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High‐efficiency Cu(In,Ga)Se2 solar cells rely on Ga grading to mitigate back surface recombination. However, the inhomogeneous absorber has drawbacks, including increased non‐radiative loss and inadequate absorption. Therefore, literatures demand a paradigm shift of using a hole‐transport layer to passivate the back surface. Herein, a functional hole‐transport layer is demonstrated as an alternative to Ga grading. The novel hole‐transport layer is prepared as a double‐layer: co‐evaporated CuGaSe2 covered by solution combustion synthesis prepared In2O3. As demonstrated by micrographs, elemental mapping, and photoluminescence spectroscopy, the oxide layer improves thermal stability and prevents Ga diffusion. However, during the absorber deposition, a complete ion exchange of In and Ga converts CuGaSe2/In2O3 into CuInSe2/GaOx. Incorporating this hole‐transport layer in co‐evaporated nongraded CuInSe2 solar cells leads to significantly increased minority carrier lifetime from 5 to 113 ns, yielding an 80 meV improvement in quasi‐Fermi‐level splitting. The devices exhibit improved open‐circuit voltage, as well as a promising fill factor of over 71%, indicating good hole‐transport properties. In these results, the passivation effect and good hole‐transport properties of the hole‐transport layer are experimentally demonstrated. Thus, high‐efficiency solar cells can be achieved by using a functional hole‐transport layer without relying on Ga grading. [ABSTRACT FROM AUTHOR]

In this study, a picosecond (ps) laser (wavelength 532 nm) with a top-hat beam was used to ablate a dielectric stack on a polished surface to improve the quality of the ablated surface. Homogeneous removal was achieved at an appropriate fluence for the ablation, since the uniform absorption of laser energy in the stack occurred by using a top-hat beam and a polished surface process. When the fluence was in the range of 0.51–0.74 J/cm2 for a top-hat beam, the direct ablation played a leading role, since more energy was absorbed in the stack rather than in the silicon, resulting in minimum damage. However, the surplus peak fluence of a ps laser with a Gaussian beam penetrated the stack and consequently caused heat shock to the silicon, and partial lift-off ablation generated thermal damage with a depth of more than 2 μm. Average efficiency of 23.40% for the passivated emitter and rear contact (PERC) cells applied with the superior ablation exceeded that for the reference cells applied with the nanosecond laser ablation with a Gaussian beam by 0.11% absolute. The significant improvement of open-circuit voltage (Voc), short-circuit current (Isc) and fill factor (FF) was mainly due to the reduced recombination at the rear contacts and decreased leakage current. The mechanisms of the laser ablation with a top-hat beam resulting in reduced damage are also applicable to other lasers with different wavelengths and can be used for improving the efficiency of other cells where a low level of damage in the ablation process is needed to decrease the surface recombination. [ABSTRACT FROM AUTHOR]

The Schockley–Quisser (SQ) limit of 28.64% is distant from the Sb2S3 solar cells' record power conversion efficiency (PCE), which is 8.00%. Such poor efficiency is mostly owing to substantial interface-induced recombination losses caused by defects at the interfaces and misaligned energy levels. The endeavor of this study is to investigate an efficient Sb2S3 solar cell structure via accurate analytical modeling. The proposed model considers different recombination mechanisms such as non-radiative recombination, Sb2S3/CdS interface recombination, Auger, SRH, tunneling-enhanced recombination, and their combined impact on solar cell performance. This model is verified against experimental work (Glass/ITO/CdS/Sb2S3/Au) where a good coincidence is achieved. Several parameters effects such as thickness, doping, electronic affinity, and bandgap are scrutinized. The effect of both bulk traps located in CdS and Sb2S3 on the electrical outputs of the solar cell is analyzed thoroughly. Besides, a deep insight into the effect of interfacial traps on solar cell figures of merits is gained through shedding light into their relation with carriers' minority lifetime, diffusion length, and surface recombination velocity. Our research findings illuminate that the primary contributors to Sb2S3 degradation are interfacial traps and series resistance. Furthermore, achieving optimal band alignment by fine-tuning the electron affinity of CdS to create a Spike-like conformation is crucial for enhancing the immunity of the device versus the interfacial traps. In our study, the optimized solar cell configuration (Glass/ITO/CdS/Sb2S3/Au) demonstrates remarkable performance, including a high short-circuit current (JSC) of 47.9 mA/cm2, an open-circuit voltage (VOC) of 1.16 V, a fill factor (FF) of 54%, and a notable improvement in conversion efficiency by approximately 30% compared to conventional solar cells. Beyond its superior performance, the optimized Sb2S3 solar cell also exhibits enhanced reliability in mitigating interfacial traps at the CdS/Sb2S3 junction. This improved reliability can be attributed to our precise control of band alignment and the fine-tuning of influencing parameters. [ABSTRACT FROM AUTHOR]

Sb2Se3, a promising thin‐film photovoltaic (TFPV) absorber material known for its non‐toxic nature, abundance on Earth, and stability has the inherent limitations of low doping density of 1013 cm−3 and poor carrier mobility of 1.5 cm2 V−1 s−1, leading to a low built‐in potential and inefficient carrier collection. To address these challenges and enhance the built‐in potential and carrier collection, an effective hole‐transport layer (HTL), e.g. CdS, which contains toxic components is used. A less‐toxic alternative is explored: ZnSe as the electron‐transport layer (ETL) to mitigate this issue. In this study, the performance is evaluated of Sb2Se3/ZnSe solar cells using six different HTLs (CuSCN, MoSe2, NiO, Spiro‐OMeTAD, SnS, MoOx) through the utilization of the SCAPS‐1D modeling tool. The HTL plays a critical role in improving the effectiveness of the built‐in potential, enhancing carrier collection, and suppressing back surface recombination. The analysis involves varying the thickness and doping concentration of the absorber, buffer, and HTLs, and exploring the impact of temperature, series and shunt resistance, and the metal work function of the back contact. Among the tested devices, the one with NiO as the HTL demonstrates the highest efficiency, exhibiting a VOC (open‐circuit voltage) of 0.81 V and a PCE (power conversion efficiency) of 24.07%. [ABSTRACT FROM AUTHOR]

Including an ultrathin insulator interlayer at the perovskite/charge transport interface is a critical strategy for suppressing surface recombination in state‐of‐the‐art perovskite solar cells. However, its further improvement with increased thickness faces a trade‐off due to the exponentially inhibited electrical transport. Here, a patterned insulator contact (PIC) design is presented to overcome this passivation‐transport trade‐off where the conventional ultrathin interlayer is replaced by a thicker counterpart with local openings. Such a PIC is realized using metal fluorides with a high coverage of 80% and a thickness tolerance increased by 3–5. Balancing inhibited transport via local openings is verified by direct observation with local photocurrent mapping. It revealed the atomic passivation mechanism of hydrogen bonding between fluoride ions and perovskite organic cations. It extends the top‐surface passivation to double‐sided passivation and find that LiF‐modified substrate improves the wettability and promotes the out‐of‐plane growth of perovskite. These combined advances and distilled knowledge allow us to achieve power‐conversion‐efficiency (PCE) of 25% (certified 24.95%) in p–i–n perovskite solar cells by simultaneously enhancing the open‐circuit voltage (Voc) and the fill factor (FF). The device's reproducibility and operational stability are also improved. [ABSTRACT FROM AUTHOR]

A decentralized energy system requires photovoltaic solutions to meet new aesthetic paradigms, such as lightness, flexibility, and new form factors. Notwithstanding, the materials shortage in the Green Transition is a concern gaining momentum due to their foreseen continuous demand. A fruitful strategy to shrink the absorber thickness, meeting aesthetic and shortage materials consumption targets, arises from interface passivation. However, a deep understanding of passivated systems is required to close the efficiency gap between ultra‐thin and thin film devices, and to mono‐Si. Herein, a (Ag,Cu)(In,Ga)Se2 ultra‐thin solar cell, with 92% passivated rear interface area, is compared with a conventional nonpassivated counterpart. A thin MoSe2 layer, for a quasi‐ohmic contact, is present in the two architectures at the contacts, despite the passivated device narrow line scheme. The devices present striking differences in charge carrier dynamics. Electrical and optoelectronic analysis combined with SCAPS modelling suggest a lower recombination rate for the passivated device, through a reduction on the rear surface recombination velocity and overall defects, comparing with the reference solar cell. The new architecture allows for a 2% efficiency improvement on a 640 nm ultra‐thin device, from 11% to 13%, stemming from an open circuit voltage increase of 108 mV. [ABSTRACT FROM AUTHOR]

Improving thermal stability is of great importance for the industrialization of polymer solar cells (PSC). In this paper, we systematically investigated the high-temperature thermal annealing effect on the device performance of the state-of-the-art polymer:non-fullerene (PM6:Y6) solar cells with an inverted structure. Results revealed that the overall performance decay (19% decrease) was mainly due to the fast open-circuit voltage (VOC, 10% decrease) and fill factor (FF, 10% decrease) decays whereas short circuit current (JSC) was relatively stable upon annealing at 150 °C (0.5% decrease). Pre-annealing on the ZnO/PM6:Y6 at 150 °C before the completion of cell fabrication resulted in a 1.7% performance decrease, while annealing on the ZnO/PM6:Y6/MoO3 films led to a 10.5% performance decay, indicating that the degradation at the PM6:Y6/MoO3 interface is the main reason for the overall performance decay. The increased ideality factor and reduced built-in potential confirmed by dark J − V curve analysis further confirmed the increased interfacial charge recombination after thermal annealing. The interaction of PM6:Y6 and MoO3 was proved by UV-Vis absorption and XPS measurements. Such deep chemical doping of PM6:Y6 led to unfavorable band alignment at the interface, which led to increased surface charge recombination and reduced built-in potential of the cells after thermal annealing. Inserting a thin C60 layer between the PM6:Y6 and MoO3 significantly improved the cells' thermal stability, and less than 2% decay was measured for the optimized cell with 3 nm C60. [ABSTRACT FROM AUTHOR]

Back‐contact perovskite solar cells offer a significant potential to reach high efficiency due to reduced parasitic absorption from the top surface. However, the currently reported efficiencies are considerably lower (<10%) than planar perovskite solar cells (>20%). Herein, back‐contact perovskite solar cells are fabricated to study loss mechanisms that cause low device efficiency. This work spatially resolves the short‐circuit current, open‐circuit voltage, photoluminescence quantum yield, carrier lifetime, and external quantum efficiency of the devices. The results indicate that the front surface recombination, increased nonradiative recombination at hole contact layer/perovskite interface, and the extraction barriers are three main mechanisms limiting devices from achieving high efficiencies. [ABSTRACT FROM AUTHOR]

Charge extraction methods are popular for measuring the charge carrier density in thin film organic solar cells and to draw conclusions about the order and coefficient of nongeminate charge recombination. However, results from such studies may be falsified by inhomogeneous steady state carrier profiles or surface recombination. Here, we present a detailed drift-diffusion study of two charge extraction methods, bias-assisted charge extraction (BACE) and time-delayed collection field (TDCF). Simulations are performed over a wide range of the relevant parameters. Our simulations reveal that both charge extraction methods provide reliable information about the recombination order and coefficient if the measurements are performed under appropriate conditions. However, results from BACE measurements may be easily affected by surface recombination, in particular for small active layer thicknesses and low illumination densities. TDCF, on the other hand, is more robust against surface recombination due to its transient nature but also because it allows for a homogeneous high carrier density to be inserted into the active layer. Therefore, TDCF is capable to provide meaningful information on the order and coefficient of recombination even if the model conditions are not exactly fulfilled. We demonstrate this for an only 100 nm thick layer of a highly efficient nonfullerene acceptor (NFA) blend, comprising the donor polymer PM6 and the NFA Y6. TDCF measurements were performed as a function of delay time for different laser fluences and bias conditions. The full set of data could be consistently fitted by a strict second order recombination process, with a bias- and fluence-independent bimolecular recombination coefficient k2 = 1.7 × 10−17 m3 s−1. BACE measurements performed on the very same layer yielded the identical result, despite the very different excitation conditions. This proves that recombination in this blend is mostly through processes in the bulk and that surface recombination is of minor importance despite the small active layer thickness. [ABSTRACT FROM AUTHOR]

Inserting an ultrathin low-conductivity interlayer between the absorber and transport layer has emerged as an important strategy for reducing surface recombination in the best perovskite solar cells. However, a challenge with this approach is a trade-off between the open-circuit voltage (Voc) and the fill factor (FF). Here, we overcame this challenge by introducing a thick (about 100 nanometers) insulator layer with random nanoscale openings. We performed drift-diffusion simulations for cells with this porous insulator contact (PIC) and realized it using a solution process by controlling the growth mode of alumina nanoplates. Leveraging a PIC with an approximately 25% reduced contact area, we achieved an efficiency of up to 25.5% (certified steady-state efficiency 24.7%) in p-i-n devices. The product of Voc × FF was 87.9% of the Shockley-Queisser limit. The surface recombination velocity at the p-type contact was reduced from 64.2 to 9.2 centimeters per second. The bulk recombination lifetime was increased from 1.2 to 6.0 microseconds because of improvements in the perovskite crystallinity. The improved wettability of the perovskite precursor solution allowed us to demonstrate a 23.3% efficient 1-square-centimeter p-i-n cell. We demonstrate here its broad applicability for different p-type contacts and perovskite compositions. [ABSTRACT FROM AUTHOR]

Successful manipulation of halide perovskite surfaces is typically achieved via the interactions between modulators and perovskites. Herein, it is demonstrated that a strong‐interaction surface modulator is beneficial to reduce interfacial recombination losses in inverted (p‐i‐n) perovskite solar cells (IPSCs). Two organic ammonium salts are investigated, consisting of 4‐hydroxyphenethylammonium iodide and 2‐thiopheneethylammonium iodide (2‐TEAI). Without thermal annealing, these two modulators can recover the photoluminescence quantum yield of the neat perovskite film in contact with fullerene electron transport layer (ETL). Compared to the hydroxyl‐functionalized phenethylammonium moiety, the thienylammonium facilitates the formation of a quasi‐2D structure onto the perovskite. Density functional theory and quasi‐Fermi level splitting calculations reveal that the 2‐TEAI has a stronger interaction with the perovskite surface, contributing to more suppressed non‐radiative recombination at the perovskite/ETL interface and improved open‐circuit voltage (VOC) of the fabricated IPSCs. As a result, the VOC increases from 1.11 to 1.20 V (based on a perovskite bandgap of 1.63 eV), yielding a power conversion efficiency (PCE) from ≈20% to 21.9% (stabilized PCE of 21.3%, the highest reported PCEs for IPSCs employing poly[N,N′′‐bis(4‐butylphenyl)‐N,N′′‐bis(phenyl)benzidine] as the hole transport layer, alongside the enhanced operational and shelf‐life stability for unencapsulated devices. [ABSTRACT FROM AUTHOR]

Larger solar cells are preferred for higher power output. However, they produce higher current and lead to higher ohmic loss. This loss has prompted manufacturers to laser cut cells into halved cells, resulting in lower current, higher voltage string‐cells. While these techniques reduce ohmic loss, they introduce cutting‐edge recombination. The monolithic solar cell resembles halved cell but without requiring cutting the original cell into strings of cells which saved the cutting‐edge recombination loss. However, we observed that the interconnection of base regions of the string‐cells on the same wafer leads to problems such as lateral forward bias current, resulting in severe degradation of the fill factor (FF) and open‐circuit voltage (VOC). Solutions to these issues are proposed including depassivated surfaces between string‐cells, optimized spacing between the string‐cells, lowered base doping density, thinner wafers, and shading regions between the string‐cells. According to simulation results, these methods could increase the efficiency of the monolithic cell to very close to the baseline cell. With the consideration of the reduced shading, ohmic loss, and module blank areas on the cell‐to‐module process, the efficiency of a module with monolithic cells could exceed that of a module with baseline cells or a module of halved/shingling cells. [ABSTRACT FROM AUTHOR]

This work aims at inspecting the device operation and performance of a novel flipped npn microstructure solar cell based on low-cost heavily doped silicon wafers. The flipped structure was designed to eliminate the shadowing effect as applied in the conventional silicon-based interdigitated back-contact cell (IBC). Due to the disappearance of the shadowing impact, the optical performance and short-circuit current density of the structure have been improved. Accordingly, the cell power conversion efficiency (PCE) has been improved in comparison to the conventional npn solar cell microstructure. A detailed analysis of the flipped npn structure was carried out in which we performed TCAD simulations for the electrical and optical performance of the flipped cell. Additionally, a comparison between the presented flipped microstructure and the conventional npn solar cell was accomplished. The PCE of the conventional npn structure was found to be 14.5%, while it was about 15% for the flipped structure when using the same cell physical parameters. Furthermore, the surface recombination velocity and base bulk lifetime, which are the most important recombination parameters, were studied to investigate their influence on the flipped microstructure performance. An efficiency of up to 16% could be reached when some design parameters were properly fine-tuned. Moreover, the impact of the different physical models on the performance of the proposed cell was studied, and it was revealed that band gap narrowing effect was the most significant factor limiting the open-circuit voltage. All the simulations accomplished in this analysis were carried out using the SILVACO TCAD process and device simulators. [ABSTRACT FROM AUTHOR]

A combination of transient and static techniques has been applied to bulk-heterojunction solar-cells to gain insight into the influence of charge-carrier dynamics and of energy level shifts in the vicinity of the cathode on the open-circuit voltage. Devices with a different thermal-annealing history but with similar active layer-morphology were compared. P3HT:PC60BM bulk heterojunction solar-cells with a standard ITO/PEDOT:PSS/active-layer/Al were investigated. We show that the open-circuit voltage increase that occurs when a sample is annealed before or after cathode deposition is due roughly one third to a shift between the energetics of the photoactive blend adjacent to the cathode and that in the bulk of the photoactive layer and roughly two thirds to a significant increase in the charge-carrier lifetime for this type of solar-cell. [ABSTRACT FROM AUTHOR]

While 2D Ruddlesden‐Popper (RP) perovskites exhibit attractive opto‐electronic properties and stability for use in perovskite solar cells (PSCs), their complicated film‐forming processes often induce a non‐negligible level of defects that significantly undermine the power conversion efficiency (PCE) and stability of PSCs. Here, the use of two organic ammonium salts with the same chain length, namely monoammonium (butylammonium iodide, BAI) and diammonium (1,4‐butanediamine dihydroiodide, BDAI2) for surface defect passivation of RP‐2D perovskite films of (AA)2MA4Pb5I16 (n = 5) are reported. It is found that the diammonium BDAI2 not only effectively reduces the defect density (similarly to using monoammonium BAI) but forms a Dion‐Jacobson (DJ) 2D structure to enhance interfacial charge extraction and suppress surface charge recombination. As a result, a boosted PCE of 18.34% has been obtained with a high open‐circuit voltage of 1.24 V. Owing to the enhanced structural integrity of the DJ phase, the RP‐2D/DJ‐2D perovskite heterojunction films exhibit supreme material robustness, which translates to the impressive environmental stability of devices, showing nearly zero‐degradation of the efficiency after 800 h of continuous thermal aging (60 °C) for 800 h. This work enriches the fundamental understanding of the impacts of the DJ‐2D structure on the surface properties of 2D perovskites. [ABSTRACT FROM AUTHOR]

• Optoelectronic characteristics of core–shell GaAs 0.99 Bi 0.01 /P3HT HSC have been investigated. • 3D finite-difference time-domain (FDTD) method has been employed for geometry optimization and optical simulation. • The E-filed profile, generation rate profiles at different wavelengths have been studied. • Radial core–shell doping profile have been used. • An extensive investigation on the variation of electrical performance parameters with carrier lifetime and surface recombination is performed for a fixed core and shell doping. The optoelectronic characteristics of the vertically aligned conformally coated radial junction, core–shell nanowire (NW) hybrid solar cell (HSC) having a core active layer of GaAs 0.99 Bi 0.01 as acceptor and donor shell layer of poly(3-hexylthiophene-2,5-diyl) (P3HT), have been investigated. Since axial junction solar cells (SCs) have been experimentally showing better efficiency as compared to their radial counterpart, our objective is to improve the efficiency of radial pn junction nanowire solar cells. In order to achieve that, the geometrical parameters, including the core diameter, shell thickness comprising P3HT layer and ITO for a fixed pitch of 480 nm are optimized. A fixed thickness of 10 nm is considered for P3HT due to a diffusion length of 20 nm. 3D finite-difference time-domain (FDTD) method has been employed to examine the effect of geometrical parameter variation on carrier generation and a detailed study has been presented. The core diameter of our proposed structure is 160 nm (R core = 80 nm) and the thickness of the surrounding shell is considered to be 90 nm (R shell = 90 nm) for further optoelectronic performance study. The absorption spectra, generation rate profile and electric field profiles for the wavelength (λ) range of 400–900 nm have been presented for depicting the improvement caused due to incorporation of conformal coating of P3HT on core GaAs 0.99 Bi 0.01 NW. An extensive investigation on the variation of electrical performance parameters such as open circuit voltage (V oc) , short circuit current (J sc) , fill factor (FF) and power conversion efficiency (PCE) with carrier lifetime and surface recombination velocity (SRV) is performed for a fixed core and shell doping. An efficiency of 19% is achieved for the device featuring minority carrier lifetime of 60 ns and sufficiently high SRV of 105cm/s at the contacts for lightly doped core (∼1 × 1016 cm−3) and heavily doped shell (∼1 × 1019 cm−3) and substrate (∼1 × 1019 cm−3). [ABSTRACT FROM AUTHOR]

Perovskites are a promising class of semiconductor materials, which are being studied intensively for their applications in emerging new flexible optoelectronic devices. In this paper, device manufacturing and characterization of quasi-interdigitated back-contact perovskite solar cells fabricated on flexible substrates are studied. The photovoltaic parameters of the prepared flexible quasi-interdigitated back-contact perovskite solar cells (FQIBC PSCs) are obtained for the front- and rear-side illumination options. The dependences of the device's open-circuit potential and short-circuit current on the illumination intensity are investigated to determine the main recombination pathways in the devices. Spectral response analysis of the devices demonstrates that the optical transmission losses can be minimized when FQIBC PSCs are illuminated from the front-side. Optoelectronic simulations are used to rationalize the experimental results. It is determined that the obtained FQIBC PSCs have high surface recombination losses, which hinder the device performance. The findings demonstrate a process for the fabrication of flexible back-contact PSCs and provide some directions for device performance improvements. [ABSTRACT FROM AUTHOR]

The transition toward thinner microcrystalline silicon wafers for their potential performance gain has been of interest in recent years. Theoretical predictions have estimated a maximum efficiency for silicon wafers to be at about 100−110 μm thickness. The potential and losses in silicon heterojunction solar cells prepared on wafers with thickness in the range of 60−170 μm with focus on open‐circuit voltage (VOC) and fill factor (FF) are studied experimentally. The applicability of thinner wafers for low light and indoor applications using light emitting diode (LED) lighting is also studied. The implied VOC (iVOC) is observed to increase with a decrease in wafer thickness according to theoretical predictions with absolute values approaching the theoretical limit. Unlike the iVOC, the implied FF is observed to decrease with wafer thickness reduction opposite to the theoretical predictions which are related to the effect of surface recombination. A combination of gains and losses results in a broad range of high efficiency under 1 sun for wafer thicknesses ranging from 75 to 170 μm with maximum of 22.3% obtained at 75 μm. As for indoor performance, thinner wafers show slightly better efficiency at lower light intensity under sun and LED illumination, promising improved performance for even thinner devices. [ABSTRACT FROM AUTHOR]

CZTSSe-based solar cell structures have shown remarkable properties in terms of their low cost, greater stability, high absorption coefficient, and relatively inexpensive production process. However, their maximum achieved values of power conversion efficiency remain low, close to 12.6%. This is mainly due to the problem of back surface carrier recombination. In this paper, we present the results of studies carried out using the SCAPS-1D tool to test the viability of deploying SnS (tin sulphide) and Sn2S3 (tin(IV) sulphide) materials as a back surface field (BSF) layer, due to their inherent advantage of having a similar material composition as CZTSSe. A detailed analysis is carried out on CZTSSe and BSF layer doping variation and CZTSSe/BSF interface defect density to optimize the photovoltaic (PV) performance of the devices. The results reflect an increase in the efficiency from 12.57% to 16.34% (with SnS BSF) and 17.04% (with Sn2S3 BSF). The cell with the SnS BSF delivers an open-circuit voltage (VOC) of 0.59V, a short-circuit current density (JSC) of 37.74 mA/cm2, and a fill factor (FF) of 73.36%, while the device with the Sn2S3 BSF delivers VOC of 0.59V, JSC of 37.68 mA/cm2 and FF of 76.46%. The results reported in this study could open a pathway to realize high-efficiency CZTSSe solar cell structures in the future. [ABSTRACT FROM AUTHOR]

A bandgap gradient at the front surface of solar absorbers can effectively suppress surface recombination while not affecting photocurrent. Herein, it is demonstrated that a front‐surface gradient can be formed in an inverted perovskite cell by introducing perovskite quantum dots (QDs) between the hole‐transporting layer (HTL) and the remaining absorber. Ultraviolet photoelectron spectroscopy reveals that, with the addition of CsPbBr3 QDs onto the HTL substrate, the subsequently deposited MAPbI3 is converted from mild p‐type to n‐type, and the resultant band alignment can effectively reduce the electron concentration at the front surface without significantly affecting hole extraction. Multiple independent characterizations further confirm the reduction of surface recombination. As a result, the inverted MAPbI3 cells exhibit an open‐circuit voltage of 1.154 V, which translates to a nonradiative recombination loss of 0.15 V and a power conversion efficiency of 20.51%. [ABSTRACT FROM AUTHOR]

In general, the conversion efficiency of solar cells decreases with the increase in temperature. This temperature dependence is mitigated by enhancing the open circuit voltage (VOC). Given a solar cell, its VOC can be enhanced by several routes, for example, reducing the defect density within the absorber, applying passivating contacts, and reducing the absorber thickness. In this work, we investigate the impact of wafer thickness in crystalline silicon (c‐Si) solar cells from the viewpoint of the photovoltaic performance at elevated temperatures. It is confirmed experimentally that the VOC of c‐Si solar cells increases by thinning the Si wafer, for example, VOC ≥ 0.75 V is obtained at a wafer thickness of <60 μm with a conversion efficiency of 22.7%, if surface recombination is sufficiently suppressed. It is also confirmed that thin c‐Si cells exhibiting high VOC show less temperature dependence. As a result, the optimum wafer thickness for maximizing the efficiency decreases with the increase in temperature according to the relation of −1.1 μm/°C. Numerical simulation predicts that this tendency becomes more emphasized with the suppression of Shockley–Read–Hall recombination. These findings suggest that the device structure of c‐Si solar cells including the choice of the wafer thickness should be optimized depending on the operating temperature in the field. [ABSTRACT FROM AUTHOR]

Nanostructured Si has attracted widespread attention due to its strong light‐harvesting ability, which is beneficial to improve the performance of solar cells. However, the poor contact of the organic/nanostructured Si interface and the large number of recombination centers on the Si surface result in an unsatisfactory open circuit voltage (VOC) and fill factor (FF) of the device. Herein, a simple and versatile method, Si nanowires modified with tetramethylammonium hydroxide (TMAH) and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) doped with 3‐glycidoxypropyltrimethoxydsilane (GOPS), is proposed to improve the contact quality of the heterojunction. TMAH treatment adjusts the morphology of the Si nanowires and makes the surface smoother, effectively inhibiting surface recombination at the heterojunction interface. Moreover, the GOPS‐doped PEDOT:PSS solution can achieve conformal contact on the surface of nanostructured Si, which is more conducive to the extraction and separation of charges. As a result, a record VOC of 660 mV is obtained for PEDOT:PSS/nanostructured Si hybrid solar cells. In addition, the short circuit current density (JSC) is as high as 33.00 mA cm−2, and the FF is as high as 69.03%; therefore, the efficiency of the device reaches 15.01%. The results provide a simple and feasible strategy to improve the junction quality and performance of organic/Si solar cells. [ABSTRACT FROM AUTHOR]

The recombination flux in a solar cell is determined by not only recombination centers, but also the spatial distribution of minority carriers. For halide perovskite solar cells (PSCs), although there has been a tremendous amount of work focusing on defect passivation, the issue of carrier distribution is not as well studied as for other types of solar cells. Here in this work, with the incorporation of perovskite quantum dots, the concept of the front surface gradient in PSCs using a solution process is successfully realized. Evidenced by multiple characterization techniques, the minority carriers are pushed away from the defect‐rich surface by the gradient of valence band maximum, which effectively reduces surface recombination without compromising photocurrent. As a result, the normal structured hybrid PSCs and MAPbI3 cells exhibit open‐circuit voltages exceeding 93% and 90% of their respective Shockley–Queisser limits, and the power conversion efficiencies reach 22.36% and 20.53%, respectively. [ABSTRACT FROM AUTHOR]

Short-circuit current, open-circuit voltage, and photoconversion efficiency of silicon high-efficiency solar cells with all back contact (BCSC) with planar surfaces have been calculated theoretically. In addition to the recombination channels usually considered in this kind of modeling, namely, radiative, Auger, Shockley-Read-Hall, and surface recombination, the model also takes into account the nonradiative trap-assisted exciton Auger recombination and recombination in the space charge region. It is ascertained that these two recombination mechanisms are essential in BCSCs in the maximum power operation regime. The model results are in good agreement with the experimental results from the literature. [ABSTRACT FROM AUTHOR]

[Display omitted] • A single junction CdS(n)/(Ag x Cu 1–x) 2 ZnSnSe 4 (p)/Cu 2 ZnSnSe 4 (p +) solar cell is presented. • Photoconversion efficiency of 18.63% is achieved from the optimized cell including different recombination mechanisms. • A relative improvement of ~47.6% in the performance of selenium rich low bandgap CZTSe solar cell is reported. • (Ag x Cu 1–x) 2 ZnSnSe 4 (ACZTSe) is used as the main absorber for better cationic ordering. • ITO is used as the back electrode to improve band bending and Schottky contact. • CZTSe is used as the back-surface field layer to prevent surface recombination. Direct bandgap Cu 2 ZnSnSe 4 (CZTSe) material is a promising absorber for thin film photovoltaics due to its affordable production cost and ecofriendly constituents. However, bulk defects, small grain size, short minority carrier lifetime and band bending at CZTSe/Mo (back contact) interface limit the performance of CZTSe solar cells. To overcome these issues, we design a single junction CdS(n)/ (Ag x Cu 1–x) 2 ZnSnSe 4 (p) /Cu 2 ZnSnSe 4 (p +) solar cell where we use (Ag x Cu 1–x) 2 ZnSnSe 4 (ACZTSe) as the main absorber layer. We have chosen the carrier density of each layer in a such way that ACZTSe becomes depleted and generated minority are collected efficiently. In our design, we utilize CZTSe as the back surface field layer to prevent surface recombination and indium doped tin oxide (ITO) as the back electrode to avoid band bending and increase the open circuit voltage. Additionally, we optimize the thicknesses of different layers and achieve a maximum efficiency of 18.63% including Shockley-Read-Hall, radiative and surface recombination mechanisms. The photo conversion efficiency (PCE) of our designed solar cell is 6 % higher (12.6% vs 18.63%) than that of the best reported selenium rich CZTSe solar cell. The design concept proposed in this work would help in harvesting solar energy efficiently from next generation CZTSe solar cells. [ABSTRACT FROM AUTHOR]

This paper describes the modeling and simulation of pristine and doped single-layer graphene/n-Si Schottky barrier solar cells (SBSCs) using finite element method software. The models utilize data from previous studies to ensure accuracy and are validated against experimental measurements. It was discovered through extensive simulations that the ideal Schottky contact model cannot completely capture fabricated devices' behavior. This led to identifying and quantifying nonideal resistive effects, possibly at the graphene-to-n-Si Schottky junction and graphene-to-metal interface, in addition to excessive device shunting effects. Other crucial parameters, such as the front surface recombination velocity, are also estimated. The study demonstrates that the optimal performance of single-layer graphene/n-Si SBSC can be achieved by carefully tuning the graphene's workfunction and the silicon's doping concentration. An optimal combination of these two parameters was found to maximize the open circuit voltage V OC and short circuit current J SC , leading to higher power conversion efficiency (PCE). [ABSTRACT FROM AUTHOR]

• The microsurface-sphericizing textures were realized on the diamond wire sawn (DWS) multi-crystalline (mc) wafers by the combination of metal-assisted chemical etching and rounding etching process. • The microsurface-sphericizing texture was helpful in reducing surface recombination and improving the electrode filling, thereby improving the electrical performance of the cells and modules. • The values of the open circuit voltage (Voc), the filling factor (FF) and the cell-to-module (CTM) loss of the cells and modules were improved with the microsurface-sphericizing process. The combination processes of metal-assisted chemical etching (AgNO 3 + HF + H 2 O 2) and rounding etching (HNO 3 + HF + H 2 O) were used for the texturization of diamond wire sawn (DWS) multi-crystalline silicon (mc-Si) wafers. The evolution of texture structure on the DWS mc-Si wafers was investigated in detail. The chemically microsurface-sphericizing (CMS) textures, which were nearly smooth spherical structure with a size of approximately 2–3 μm, were fabricated successfully on the DWS mc-Si wafers with the combination processes. Compared with the conventional metal-assisted chemical etching (MACE) textures, the CMS textures were improved on surface recombination and the filling of electrode, thereby boosting the electrical performance of the solar cells and the cell-to-module (CTM) loss at the module end. These CMS textures resulted in an increase in the output power of the photovoltaic module by 0.047 W per cell. The fabrication of these CMS textures may be easily scaled up in the photovoltaic production line. [ABSTRACT FROM AUTHOR]

Solar cells are semiconductor devices that turn light into electricity. The performance analysis of a Gallium Arsenide (GaAs) based solar cell model was shown using the Analysis Microelectronic and Photonic Structures (AMPS-1D) simulator in this work. A balance of semiconductor compositions, layer thicknesses, and other factors had been studied. The effect of temperature on efficiency has been explored, as the thickness of the top gallium indium layer (GaInP). As the amount of phosphorus in double junction solar cells decreases, the efficiency increases. An efficient and optimised BSF layer is a key layer in both single junction and multi junction solar cells. The use of dual layer BSF for top cells with different thicknesses is explored in this GaInP/GaAs dual junction solar cell study using the Silvaco ATLAS computer numerical simulation TCAD tool. A low-high junction at the back end of a gallium arsenide solar cell has been studied. A back surface field (BSF) is generated by the n+ layer at the rear end of a standard p+ n junction solar cell, which improves the open-circuit voltage, short circuit current, fill factor, efficiency, and spectrum response. [ABSTRACT FROM AUTHOR]

The relationship of the temperature–light intensity dependence of open‐circuit voltage Voc in nonfullerene‐based organic solar cells with their material characteristics and multimechanism recombination parameters is described. The systematic variation of the effective bandgap Eg,eff and the electrode layers allows the observation of different relative contributions of bimolecular, bulk, and surface trap‐assisted recombination mechanisms. The complementary advantages of the analytical model and the established voltage‐impedance spectroscopy technique provide a useful tool to quantify multimechanism recombination parameters, effective density of states Nc, and energetic disorder σ in organic solar cells under operating conditions. The validity of the proposed model to understand the temperature and light intensity dependent of Voc is shown by applying it to four different donor:nonfullerene acceptor blend systems with conventional or inverted device architectures. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of state‐of‐the‐art organic solar cells is still limited by significant open‐circuit voltage (VOC) losses, partly due to the excitonic nature of organic materials and partly due to ill‐designed architectures. Thus, quantifying different contributions of the VOC losses is of importance to enable further improvements in the performance of organic solar cells. Herein, the spectroscopic and semiconductor device physics approaches are combined to identify and quantify losses from surface recombination and bulk recombination. Several state‐of‐the‐art systems that demonstrate different VOC losses in their performance are presented. By evaluating the quasi‐Fermi level splitting (QFLS) and the VOC as a function of the excitation fluence in nonfullerene‐based PM6:Y6, PM6:Y11, and fullerene‐based PPDT2FBT:PCBM devices with different architectures, the voltage losses due to different recombination processes occurring in the active layers, the transport layers, and at the interfaces are assessed. It is found that surface recombination at interfaces in the studied solar cells is negligible, and thus, suppressing the non‐radiative recombination in the active layers is the key factor to enhance the PCE of these devices. This study provides a universal tool to explain and further improve the performance of recently demonstrated high‐open‐circuit‐voltage organic solar cells. [ABSTRACT FROM AUTHOR]

• The optimal cleaning process combined inline-HF/HNO 3 and batch-polish solution. • Cells with low I Rev 0.15A have good optical property after optimal cleaning process. • Developed wraparound model addressed the principle of cleaning process. • A pilot efficiency >23.53% of TOPCon cells cleaned with optimal process. The use of tunnel oxide passivated contact (TOPCon) solar cells on the n-type Cz-Si wafers has thus far attracted more interest in the photovoltaics (PV) industry. However, the cells encounter the problems of wraparound appearance and edge leakage current. These phenomena can result in the decrease in the optical and electrical performance of the cells, such as open circuit voltage (V oc), short-circuit current density (J sc), and fill factor (FF). In this work, several cleaning processes were adopted to resolve the problems for cells. The wraparound model and experimental results indicated that an effective cleaning process was carried out and revealed the correlation between the removal of the wraparound film and the edge junction layer on the surface of wafers. The optimized cleaning process did not destroy the boron-doping layer on the front side, and the poly-Si layer on the rear side. This process combined an inline etching process of HF/HNO 3 treatment and a batch-type etching process of the KOH/polish additives solution treatment, which could effectively solve the problems associated with optical properties and achieve a low reversed-biased junction leakage current (I Rev) 0.15 A at −14.5 V. After optimization of the rear surface recombination and the boron diffusion processes, industrial-type TOPCon cells at the present pilot line were obtained with the efficiency (E ff), V oc , J sc and FF of 23.53%, 706 mV, 40.65 mA/cm2 and 82.02%, respectively. This optimized cleaning process could be applied and promoted in the PV industry. [ABSTRACT FROM AUTHOR]

Solar cells manufactured on top of Ge substrates suffer from inherent drawbacks that hinder or limit their potential. The most deleterious ones are heavy weight, high bulk recombination, lack of photon confinement, and an increase of the heat absorption. The use of thinned Ge substrates is herein proposed as a possible solution to the aforementioned challenges. The potential of a thinned Ge subcell inside a standard GaInP/Ga(In)As/Ge triple‐junction solar cell is assessed by simulations, pointing to an optimum thickness around 5–10 μm. This would reduce the weight by more than 90%, whereas the available current for the Ge subcell would decrease only by 5%. In addition, the heat absorption for wavelengths beyond 1600 nm would decrease by more than 85%. The performance of such a device is highly influenced by the front and back surface recombination of the p–n junction. Simulations remark that good back surface passivation is mandatory to avoid losing power generation by thinning the substrate. In contrast, it has been found that front surface recombination lowers the power generation in a similar manner for thin and thick solar cells. Therefore, the benefits of thinning the substrate are not limited by the front surface recombination. Finally, Ge single‐junction solar cells thinned down to 85 μm by wet etching processes are demonstrated. The feasibility of the thinning process is supported by the limited losses measured in the current generation (less than 6%) and generated voltage (4%) for the thinnest solar cell manufactured. [ABSTRACT FROM AUTHOR]

We fabricate and characterize methylammonium lead halide perovskite film as a novel back contact to CdTe thin‐film solar cells. We apply ~0.75 μm perovskite film at the interface of CdCl2‐activated and Cu‐doped CdTe surface and complete the device with Au back contact. We use Cu/Au back contact as a reference to compare results with novel back contact. Our investigation shows that incorporation of thin layer of perovskite film before the back contact metal reduces back contact barrier effect and improves fill factor (FF) and open‐circuit voltage (VOC) of the solar cells. Our low temperature JV results prove that thin‐film perovskite is a very necessary component in CdTe solar cells to reduce back contact barrier, to minimize interface or surface recombination, to improve collection efficiencies, and to increase the efficiency of solar cells. Our best device shows 7% increase in VOC to 0.875 V and ~7% increase in FF with the highest FF of 81%, and solar cell's efficiency finally increases by 10% with the use of MAPb(I1‐xBrx)3 as an interface layer. [ABSTRACT FROM AUTHOR]

• A novel heterostructure (ITO/CeO 2 /SnS/NiO/Mo) of SnS-based solar cell has been designed and simulated. • NiO HTL has enhanced the open circuit voltage by 345 mV. • Maximum PCE of 25.1% has been achieved with V OC of 0.890 V, J SC of 32.67 mA/cm2, and FF of 86.19%, respectively. In this article, the numerical investigations on a novel (ITO/CeO 2 /SnS/NiO/Mo) heterostructure of the SnS-based solar cell have been presented using SCAPS-1D simulation software. The main objective of the study was the exploration of the effect of NiO hole transport layer (HTL) on the performance of the proposed SnS-based heterojunction solar cell. The open circuit voltage of the proposed cell has been enhanced up to 345 mV after using NiO HTL which indicates a significant reduction of surface recombination velocity at SnS/electrode interface. Around 12.78% efficiency enhancement was observed after using NiO HTL in the SnS-based heterojunction solar cell, and an efficiency of 25.1% could be obtained from the proposed heterojunction solar cell. It was found that the cell performance depended on the carrier concentration and thickness of the CeO 2 electron transport layer (ETL), SnS absorber layer, and NiO HTL, respectively. The effects of deep level defect density of the SnS absorber layer and interface defect density of NiO/SnS and CeO 2 /SnS on the cell performance ware also studied. These findings reveal that the NiO could be a promising HTL for the fabrication of low cost, high-efficiency SnS-based heterojunction solar cell. [ABSTRACT FROM AUTHOR]

The junction properties at the solution-processed titanium dioxide (TiO2)/n-type crystalline Si(n-Si) interface were studied for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/n-Si heterojunction solar cells by the steady-state photovoltaic performance and transient reverse recovery characterizations. The power conversion efficiency could be increased from 11.23% to 13.08% by adjusting the layer thickness of TiO2 together with increasing open-circuit voltage and suppressed dark saturation current density. These findings originate from the enhancement of the carrier collection efficiency at the n-Si/cathode interface. The transient reverse recovery characterization revealed that the surface recombination velocity S was ∼375 cm/s for double TiO2 interlayer of ∼2 nm thickness. This value was almost the same as that determined by microwave photoconductance decay measurement. These findings suggest that solution-processed TiO2 has potential as a hole blocking layer for the crystalline Si photovoltaics. [ABSTRACT FROM AUTHOR]

Passivation contact (PSC), which simultaneously achieves high passivation quality and low contact resistivity, has been proven to be a delicate design to fabricate high‐efficiency solar cells (SCs). However, traditional PSC materials, that is, intrinsic a‐Si:H/doped a‐Si:H or tunnel SiO2/doped poly‐Si, overly rely on the complex procedures and have inevitable optical or Auger recombination losses. Herein, a novel low‐temperature oxidation (LTO) process is developed and an electron‐selective TiOx film (LTO‐TiOx) is fabricated, reaching a low‐effective surface recombination velocity of 13.7 cm s−1. The high‐quality passivation performance is mainly attributed to the chemical passivation of Ti–O–Si bonds and the surface carrier manipulation ability of the LTO‐TiOx film. Next, by adding a low work function (WF) layer of LiFx film, the surface band bending effect is formed and the contact resistivity of TiOx‐based PSC is also optimized. Furthermore, the dual‐functional LTO‐TiOx/LiFx electron‐selective PSC is integrated in Si SCs and a champion efficiency is achieved near 19% with an open‐circuit voltage near 640 mV. Finally, a comprehensive simulation analysis indicates a high efficiency of more than 22% based on LTO‐TiOx PSC, followed by a detailed roadmap of efficiency improvements, demonstrating its huge application potential in SCs. [ABSTRACT FROM AUTHOR]

• Replacing commonly used ZnO EEL with PEI can eliminate UV-induced V oc loss of OSCs. • Unlike ITO/ZnO, ITO/PEI contacts maintain their hole blocking functionality. • UV-induced surface recombination and contact's charge selectivity losses are shown. • A correlation between reduced contact selectivity and a UV-induced V oc loss is shown. The effect of using Polyethylenimine (PEI) instead of ZnO in the electron extraction layers (EELs) of inverted organic solar cells (OSCs) on their photo-stability behavior is investigated. Studies on inverted OSCs based on two different donor/acceptor bulk heterojunction material systems show that replacing ZnO by PEI substantially reduces the open-circuit voltage (V oc) loss in OSCs that is often observed under prolonged UV irradiation. Analysis of current density-voltage characteristics of the solar cells as well as of hole-only devices shows that the higher V oc stability attained upon using PEI instead of ZnO is mainly due to the ability of the ITO/PEI contact to maintain a higher degree of electron selectivity and hole blocking properties under UV exposure in comparsion to the ITO/ZnO contact. Using V oc vs light intensity analysis, a UV-induced transition in the dominant recombination mechanism from a trap-assisted bulk recombination mechanism to a surface recombination one at the contacts is found to occur in solar cells with ZnO EELs. Similar tests on PEI show that it suppresses that increase in surface recombination and confirms its ability to maintain the hole blocking properties of the contact upon UV exposure. This study provides a direct observation of increased surface recombination in OSCs due to UV irradiation and direct evidence of the importance of maintaining charge selectivity of contacts to suppress surface recombination and maintain high V oc photo-stability. [ABSTRACT FROM AUTHOR]

The present work addresses the exhaustive study of the surfaces of multicrystalline silicon wafers after being subjected to a texturization process for silicon heterojunction solar cell applications. The investigations described include the effect that the time of isotropic etching based on combinations of hydrofluoric and nitric acids has on the reflectance, the morphology of the surfaces and the surface recombination through the evolution of the implicit open-circuit voltage. The influence of previous treatments and the elimination of porous silicon or silicon oxide formed on wafer surfaces as a consequence of these texturization processes are also addressed. Textured multicrystalline silicon wafer surfaces with a good uniformity and low weighted hemispherical reflectances (23–24%) have been achieved with short etching times. These texturization processes have also been tested on upgraded metallurgical silicon wafers, resulting in weighted hemispherical reflectance values around 23%, but at the cost of the appearance of important surface defects. [ABSTRACT FROM AUTHOR]

Substantial improvement of the open-circuit voltage of thin film solar cells has been investigated by applying an electron reflector strategy. Cd 1- x Mg x Te has a strong potential as an electron reflector to keep minority carriers away from the CdTe back surface to reduce the back surface recombination. In this paper, SCAPS simulations were first used to investigate device performance for CdTe solar cells with the electron reflector layers. The theoretical results indicate that the ∼0.4 eV electron barrier height for CdTe solar cells with Cd 1- x Mg x Te (E g ∼1.85 eV) is sufficient to decrease the back surface recombination and improve device performance, especially the open-circuit voltage. Thus the variation of energy gap of the Cd 1- x Mg x Te thin films prepared by coevaporation as a function of x was investigated from the transmittance spectra. Then Cd 1- x Mg x Te (x ∼0.3) thin films were used as the electron reflectors for the CdTe thin film solar cells. It is found that CdTe solar cells with Cd 1-x Mg x Te yielded open-circuit voltage of 804 mV and fill factor more than 70% after an 425 °C anneal, which is higher than those without Cd 1- x Mg x Te. The electron reflector in CdTe solar cells can effectively reduce the carrier surface recombination, thereby resulting in the increase of the fill factor and the open-circuit voltage. The wide bandgap material, CMT with a negligible valence band offset to CdTe, was proposed to be inserted prior to the back contact to reduce the recombination of the photo-generated carriers by reflecting them back to the main junction. Significant improvements in cell performance have been achieved for CdTe solar cells. Image 10816 • SCAPS simulations were used to investigate device performance for CdTe solar cells with an electron reflector layer. • The ∼0.4 eV barrier height for CdTe solar cells with CMT (∼1.85 eV) is sufficient to decrease the back surface recombination. • CMT thin films were prepared by vacuum coevaporation. • Significant enhancements in open-circuit voltage and fill factor for CdTe solar cells were achieved. • Enhanced device performance is ascribed to the introduction of an electron reflector structure. [ABSTRACT FROM AUTHOR]

• Three absorber bandgap gradation structures respectively were simulated to seek optimization of the CTGS based thin film solar cell performance. • The effects of the two different back contact metal working function on device performance were calculated. • The effects of various bulk defects of CTGS absorber on solar cell properties were investigated. • The depth profile of the carrier recombination rate was calculated to understand of the fundamental device physics. The bandgap of the ternary chalcogenide Cu 2 SnS 3 (CTS) can be tuned by alloying with Ge. The performance of CTS based solar cell devices with varies band gap grading profiles have been simulated with respect to the solar cells with a uniform band gap absorbing layer. It was revealed that band gap engineering geared to controlling the grading profile in the absorber layer lead to performance enhancement comparing to that of a device without band gap grading. Moreover, bandgap profiles with various back metal working function (φ m) were simulated. An over 4–5% efficiency improvement was obtained due to the increasing φ m with different band gap grading profile. The optimum PCE of 15.65%, 19.03% and 19.9% have been obtained with uniform, single and double band gap structures respectively. Moreover, the effects of various defects density on solar cell properties were investigated and the results indicate that there is a threshold of 1 × 1016 cm−3 for both acceptor/donor and neutral defects. The depth profile of the carrier recombination rate was calculated to understand of the fundamental device physics. The result show that a great improvement of both V oc and J sc was obtained in the back surface grading structure cell comparing to that of the uniform bandgap cell due to the additional quasi-electric field associated to the affinity (conduction band) variation with position benefitting the carrier collection and reducing the back surface recombination and bulk recombination typically characterized by the diffusion length. A slight enhancement of short-circuit current density without significantly sacrificing the open-circuit voltage was obtained in the double band gap grading structure comparing to the single back grading owing to an increasement of front grading within the SCR. [ABSTRACT FROM AUTHOR]

Thin crystalline silicon (c‐Si) solar cells are highly attractive for realizing light‐weight and flexible wafer‐based solar cells as well as for reducing the material cost. Silicon heterojunction (SHJ) architecture using hydrogenated amorphous silicon (a‐Si:H) is suitable for realizing very thin c‐Si cells, because of its capability of excellent surface passivation. In this work, the potential of very thin c‐Si solar cells is examined by characterizing SHJ solar cells with a wide range of thicknesses from 50 to 400 μm. A trade‐off between the open‐circuit voltage (VOC) and the short circuit current density (JSC) against wafer thickness is clearly observed in these SHJ cells, whereas a decrease in fill factor (FF) is found for thin SHJ cells below 80 μm. The loss analysis for the thin SHJ cells with numerical simulation clarifies that the infrared parasitic absorption loss due to the supporting layers is enhanced for thinner wafers, which limits the JSC in the thin SHJ cells. In addition, it is confirmed that the FF is more sensitive to surface recombination than the VOC, and this tendency becomes more pronounced with the decrease in the wafer thickness. A high efficiency of 22% is achieved in a SHJ solar cell with a thickness of only 46 μm, demonstrating a high potential for flexible high‐efficiency c‐Si solar cells. [ABSTRACT FROM AUTHOR]

The p/n heterojunction with low surface recombination losses and good band alignment is one of the key factors for obtaining efficient photovoltaic (PV) devices. Here, ultrathin Al 2 O 3 is introduced, and the effects of its thickness and growth temperature on the PV performance of Cu 2 ZnSn(S,Se) 4 (CZTSSe) solar cells are investigated. The result indicates that the increased depletion width and built-in voltage after appropriate Al 2 O 3 treatment promote the separation and transport of photogenerated carriers. The absorber surface composition and defect are optimized, and the interface band alignment is modified by reducing the conduction band offset successfully, which drives the carrier collection and increases open-circuit voltage by 60 mV. The dual passivation mechanism of chemical passivation and field-effect passivation is realized by introducing Al 2 O 3 into kesterite solar cells. This work not only reveals the intrinsic mechanism for performance enhancement CZTSSe solar cells with Al 2 O 3 , but also provides a significant guidance for the band adjustment at the interface. • Band alignment at p/n heterojunction is tailored by appropriate Al 2 O 3. • The appropriate Al 2 O 3 induces surface modification and crystallization. • W d and V bi are increased to facilitate carrier separation and transmission. • The field-effect passivation and chemical passivation mechanisms are realized. • It reveals intrinsic origin for performance enhancement of CZTSSe with Al 2 O 3. [ABSTRACT FROM AUTHOR]

One of the most significant features of lead-halide perovskites is their ability to have comparably slow recombination despite the fact that these materials are mostly processed from solution at room temperature. The slow recombination allows achieving high open-circuit voltages when the lead-halide perovskite layers are used in solar cells. This perspective discusses the state of the art of our understanding and of experimental data with regard to recombination and open-circuit voltages in lead-halide perovskites. A special focus is put onto open questions that the community has to tackle to design future photovoltaic and optoelectronic devices based on lead-halide perovskites and other semiconductors with similar properties. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'. [ABSTRACT FROM AUTHOR]

The key parameters of silicon solar cells with back contact and rear metallization (SC-BC), such as the short-circuit current, open-circuit voltage, and photoconversion efficiency are modeled theoretically. Among other recombination channels, the model accounts for the non-radiative Auger recombination assisted by the deep recombination center and recombination in the space-charge region. It has been ascertained that these mechanisms are important in the typical commercial SC-BC in the maximal-power regime. The theory has been developed for calculating the efficiency as a function of the SC-BC thickness. Experimental and theoretical data agree well between each other. In particular, the theory has been applied to model the SC-BC produced by SunPower Corp. Depending on the surface recombination velocity on the illuminated surface and on the total surface recombination velocity on the front and rear surfaces, two mechanisms determine the optimal SC-BC thickness, at which the output power reaches its maximal. The first mechanism dominates, when the efficiency exceeds 24% under the AM1.5 conditions and is related to an essential increase of photon mean free path in the textured silicon SC. The other mechanism, more pronounced in the SC-BC with the efficiency below 22%, imposes limitations on the optimal thickness due to the surface recombination on the front SC-BC surface. [ABSTRACT FROM AUTHOR]

ZnO-silicon heterojunction solar cell having high efficiency and high fill factor is structured and simulated to study its photovoltaic properties under different device temperature. Current-voltage measurement of dimensionally optimised device structure revealed up to 20.44% efficiency and 83.66% fill factor at 1 ν-cm2 external series resistance at 300 K. Measured current-voltage shows decrease of open-circuit voltage from 659.13 to 109.1 mV and short-circuit current from 40.65 to 39.5 mA/cm2 with increase of device temperature. Quasi-steady-state photoconductance measurement reveals small recombination current and long Shockley Read Hall lifetime under the selected temperature range indicating superior performance of the device. Adverse effect of surface recombination velocity at rear surface of the device is observed at lower temperature (100-600 K) range indicating better majority carrier collection at very high temperature 700 K and above. [ABSTRACT FROM AUTHOR]

In this work, a numerical simulation study on cadmium telluride (CdTe)-based thin film solar cell structure utilizing CdTe as absorber layer, Cadmium sulphide (CdS) as window layer, and lead-free perovskite (CH 3 NH 3 SnBr 3) as a hole transport layer (HTL) is presented for the first time. The effect of different material parameters such as shallow uniform acceptor density (N A) of absorber and HTL, thicknesses of absorber and HTL, Electron affinity of HTL, defect density of absorber layer, series and shunt resistance, back contact metal work function, and operating temperature on photovoltaic (PV) parameters such as open-circuit voltage (V oc), short circuit current (J sc), fill factor (FF), and photo conversion efficiency (PCE) has been studied. With the introduction of perovskite as HTL, it is observed that V oc increased from 0.66 V to 1.17 V by creating a suitable band alignment with the CdTe absorber layer, causing an improvement in efficiency by preventing carrier recombination at the back contact surface. The designed solar cell has shown an enhanced PCE of 27.10% with V oc ∼1.17 V, J sc ∼27.76 mA/cm2, and FF ∼83.40%. Thus, from the study, it is possible to achieve high-performance CdTe-based solar cells using perovskite as HTL for photovoltaic applications. • Perovskite as a HTL has been explored for the first time in CdTe-based thin film solar cell. • The band alignment of methyl ammonium tin bromide is suited with CdTe. • With the introduction of tin-based perovskite, enhanced V oc ∼1.17 V and efficiency ∼27.10% is observed. • Back Surface Field causes a significant decrease in the surface recombination loss and increase in the carrier collection. • Perovskite as HTL has a great impact on the stability and photovoltaic performance of solar cell. [ABSTRACT FROM AUTHOR]

In this paper, we report on the current status of absorber attributes in Liquid Phase Crystallized Silicon (LPC-Si) cells. To this end, an absorber doping series ( N D = 2·10 16 /cm³ to 7·10 17 /cm³) and an absorber thickness variation (14 and 33 µm) are evaluated. Best cells from the batches for these series showed open circuit voltages up to 640 mV and fill factors above 70%. It is observed that for state-of-the-art cells, thicknesses over 15 µm are not beneficial due to limited diffusion lengths. Lower absorber doping concentrations tend to yield longer intra-grain diffusion lengths ( L diff ) and better passivated grain boundaries, which may be due to lower impurity precipitation. The longer L diff leads to higher short circuit current densities which over-compensate a decrease in open circuit voltage and fill factor with regards to efficiency. Both front and rear surfaces are sufficiently passivated and at the current status the bulk lifetime has most potential for improvement. [ABSTRACT FROM AUTHOR]

Lead chalcogenide colloidal quantum dot solar cells (CQDSCs) have the potential to revolutionize the field of light-to-electricity conversion with their exceptional optoelectronic properties. Unfortunately, realizing their full potential has been hindered by persistent and poorly understood limitations in fill factor (FF) and open-circuit voltage (V oc) losses. In this study, we performed a systematic numerical analysis of practical PbS CQDSCs to identify the root causes of FF and V oc losses in the current development stage, and to provide a clear and feasible roadmap for achieving a PCE of more than 20% in future development stages. Our analysis revealed that the highly effective route for enhancing the current 10% device is to initially modify the internal resistances, resulting in a significant reduction in FF losses to 15%, followed by systematic optimization of surface recombination velocities in the absorber layer and the absorber/hole transfer layer (HTL) interface, which can generate a V oc improvement of 3.76%, ultimately leading to a near-15% PCE. To further elevate PCE to unprecedented heights, we identified the precise regulation of surface excess charge densities at the absorber/HTL interface and the HTL/back contact interface as critical factors. By finely tuning these performance-limiting factors, we demonstrated the feasibility of achieving over 20% PCE, with minimal V oc loss of 318.10 mV and almost negligible FF loss of 6.08% in PbS CQDSCs. Our investigation provides crucial insights into the causes of FF and V oc losses in PbS CQDSCs and offers a clear pathway for future progress in this rapidly evolving field. [ABSTRACT FROM AUTHOR]

The selectivity of electrodes of solar cells is a critical factor that can limit the overall efficiency. If the selectivity of an electrode is not sufficient both electrons and holes recombine at its surface. In materials with poor transport properties such as in organic solar cells, these surface recombination currents are accompanied by large gradients of the quasi-Fermi energies as the driving force. Experimental results from current-voltage characteristics, advanced photo- and electroluminescence as well as charge extraction of three different photoactive materials are shown and compared to drift-diffusion simulations. It can be concluded that in cases of electrodes with reduced selectivity the decrease of the open-circuit voltage can be divided into two distinct contributions, the reduction of the overall steady-state charge carrier density and the gradients of the quasi-Fermi energies. The results clearly show that for photoactive layers with poor transport properties, the gradient of the quasi-Fermi energy in the vicinity of the contact is the main contribution to the loss in open-circuit voltage. For imbalanced mobilities, this gives rise to the phenomenon that it is more challenging to realize a selective contact for the less mobile charge carrier, i.e., the hole contact in most organic solar cells. [ABSTRACT FROM AUTHOR]

Heat generation via Interface recombination in CZTSSe/CdS kesterite thin film solar cells has been investigated using a simulation model by coupling the thermal, electrical, and optical modules. Three interface defects (Cu Sn , Cu Zn , Sn Zn) located at different energy levels were considered. The defect closer to the midgap (Cu Sn at 0.55 eV) generate the highest heat power and increasing the defect density from 1014 cm−3 to 1018 cm−3 raised the interface heat generation from 60 W/cm2 to 80 W/cm2. This is nearly half of heat generation rate for Cu Zn defect located near the valence band. H surf raised from 60 W/cm2 to 74 W/cm2 by increasing the surface recombination velocity (S). This detailed simulation analysis recognizes the significant role of interface recombination and its contribution to heat generation and thermal stability in solar cells and demonstrates the importance of interface quality and interface engineering strategies in such devices. [ABSTRACT FROM AUTHOR]