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Regardless of the fact that the confirmed Power Conversion Efficiency (PCE) of kesterite materials for photovoltaic cells is lower than that of other chalcogenide materials, there is still sign of improvement due to their high absorption rate, flexibility to have a tunable bandgap, abundance in nature, and so on.The primary objectives of this study was to assess the combined utilisation of quantum dots and quantum wells in kesterite material. This was achieved through three key approaches: firstly, by altering the quantity of quantum dots and wells present in the nanostructure; secondly, by modifying the composition of the dots and well material through adjustments in the Sulphur and Selenium ratio of CZTSSe. The third aspect to consider is the analysis of the effect of changes in operating temperature on high-performing nanostructures, building upon the information gathered from the previous two processes. Electrical properties such as PCE, $ V_{oc}$ , $ J_{sc}$ , and IV curve have been analyzed so that the performance of the hybrid structure can be examined. A quantum well and a quantum dot layer are both present in the p-i-n structure. The quantum dot layer is composed of ten quantum dots placed in an array. The effects of quantum dot thickness (5 and 10 nm) were also investigated. According to the findings, as few as three quantum dot layers and three quantum wells resulted in a 21% PCE. By varying the operating temperature between 250 K to 500 K, the temperature dependency of high-PCE structures was examined. [ABSTRACT FROM AUTHOR]

There is a plethora of thin-film photovoltaic materials like copper indium gallium sulfur (CIGS), CIGS-Selenium (CIGSSe), Cu2ZnSnS4 (CZTS), $\text {Cu}_{{2}}\text {ZnSn} (\text {S}_{x}, \text {Se}_{{1}-{x}})_{{4}}$ (CZTSSe), and so on that are currently under research and are suitable for commercial use. In this study, a Cu2CdSnS4 (CCdTS)-based thin-film solar cell is simulated using Silvaco technology computer-aided design (TCAD) to extract its optical and electrical properties such as efficiency, electric field (EF), short circuit current, quantum efficiency, and so on. The device is also optimized by variations in physical parameters such as thickness, doping concentration, and material defects of the absorber layer. A remarkable efficiency of 21.2% is reached under the condition of defect absence, whereas the efficiency of 7.5% is obtained for the defect present in the absorber layer. Changes in the behavior of the solar cell with material defects following Gaussian- and tail-type distribution are also analyzed and corresponding conclusions are drawn. [ABSTRACT FROM AUTHOR]

In this work, we have investigated perovskite-based solar cells (PSCs) with seven different organic hole transport layers (HTLs), which include spiro-2,2’,7,7’-Tetr- akis-(N, N-di-4-methoxyphenylamino) −9,9’-spirobifluorene (OMeTAD), poly(triaryl amine) (PTAA), poly (3,3”’-dialkyl- quaterthiophene) (PQT), poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), poly (3-hexylthioph- ene-2,5-diyl) (P3HT), Poly [2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), and n-Propyl Bromide (nPB). This article reports the impact of several device parameters, such as perovskite layer defect density, and thickness, on the solar cell performance. We examined the device performance for the PSC device architecture, i.e., fluorine-doped tin oxide (FTO)/TiO2/CH3NH3PbI3/HTLs/Au. For this study, numerical simulation has been performed and optimized for optimum absorber layer thickness and defect density. In this study, we report the power conversion efficiency (PCE) with various HTLs, such as 10.01% for MEH-PPV, 13.94% for PEDOT:PSS, 14.75% for P3HT, 15.42% for PQT, 15.74% for NPB, 17.08% for PTAA, and 17.11% for spiro-OMeTAD at an optimized thickness of 300 nm. It is asserted that there is an enhancement in the photovoltaic performance observed while using spiro-OMeTAD and PTAA as HTL. PSC using spiro-OMeTAD as HTL shows exceptional performance compared to other HTLs. Other parameters obtained for PSC using spiro-OMeTAD are ${V}_{OC}$ of 1.10 V, ${J}_{SC}$ of 20.772 mA/cm2, FF of 0.74%, and PCE of 17.11%. The elicited simulation results suggest that spiro-OMeTAD is the most promising candidate for HTL to fabricate low-cost, highly efficient, and low-temperature processed hybrid PSC. [ABSTRACT FROM AUTHOR]

The formamidinium lead triiodide (FAPbI3)-based perovskite solar cell (FPSC) is perceived as a potential replacement of conventionally exploited methylammonium lead triiodide (MAPbI3)-based PSC owing to its better stability. In this work, we explore the possibility of utilizing molybdenum disulfide (MoS2) as a prospective replacement of conventional titanium dioxide (TiO2) (requires high processing temperature) as an electron transport layer (ETL) in FPSC using SCAPS-1D. The results are quantitatively compared in terms of the performance metrics of simulated baseline models. Furthermore, the performance variations are also compared with respect to varying absorber layer defect density. Moreover, the reproducibility aspect of cells is compared with respect to varying carrier mobility of the absorber layer. We observe an outstanding improvement in efficiency and reproducibility of FPSCs with MoS2 as ETL. The results highlight the vitality of ETL material properties toward efficiency and reproducibility enhancement of FPSCs. These findings serve as an important benchmark for improving the commercialization prospects of FPSCs. [ABSTRACT FROM AUTHOR]

In this work, a lead-free Cs3Sb2Br9 perovskite material is used as wide bandgap material (WBG) for top cell of the all-perovskite tandem device for the first time. A comparative study between the commonly used lead-based organic MAPbI3 and lead-free CsSn0.5Ge0.5I3 is performed for narrow bandgap material (NBG) for the bottom cell of the all-perovskite tandem solar cell (TSC). The current matching conditions between WBG top cell and both NBG bottom cells are observed through the variation in the thickness of perovskite materials. The effects of bottom absorbers’ thickness, absorber defect density, and carrier lifetime for both NBG perovskite solar cells (PSCs) are also investigated. Both the all-perovskite TSCs achieved excellent performance with Cs3Sb2Br9/CsSn0.5Ge0.5I3 TSC yielding a maximum power conversion efficiency (PCE) of 20.63% with ${V}_{\text {OC}}$ of 2.19 V, ${J}_{\text {SC}}$ of 10.64 mA $\cdot $ cm $^{ -{2}}$ , and fill factor (FF) of 88.53%, respectively. The CsSn0.5Ge0.5I3-based TSC demonstrated better tandem device due to all-inorganic structure with higher carrier mobility, higher effective density of state, better stability, and environment-friendly conditions under external conditions, which highlights the viability of Cs3Sb2Br9/CsSn0.5Ge0.5I3 TSC for commercial photovoltaics (PV) technology. [ABSTRACT FROM AUTHOR]

This present work emphasizes the numerical modeling of lead-free methylammonium tin tri-iodide (MASnI3)-based perovskite solar cells (PSCs) under optimizing preconditions. The prior selection of the perovskite material of MASnI3 is feasible for a more extended absorption spectrum due to a smaller bandgap of 1.3 eV than higher bandgap methylammonium lead tri-iodide (MAPbI3)-based PSC and the factor of lesser toxicity. Furthermore, to enhance the efficiency of the device, selecting potentially steadier and superior carrier transport materials (CTMs) is among the most effective approaches for optimizing device outputs. Among the proposed materials, a prior selection of copper antimony sulfide (CuSbS2) and zinc oxide (ZnO) as CTMs with an optimized thickness of MASnI3 material has offered a higher power conversion efficiency (PCE) of 22.16% under the photoillumination AM1.5. Furthermore, the less-defective PSC device can also be helpful for further device optimization and futuristic development. [ABSTRACT FROM AUTHOR]

We propose an n-ZnO/p-SnOx heterojunction solar cell as a novel pathway to realize all-oxide photovoltaics that offer attractive features such as stability, cost-effectiveness, and nontoxicity. TCAD device simulator was used to investigate the performance of n-ZnO/p-SnOx thin-film solar cell using inputs on material parameters of SnOx obtained experimentally. In this study, we considered the effects of SnOx parameters, namely, bandgap and electron affinity on the performance of solar cell. Electrical transport models applied in modeling include the effects of interfacial recombination, tunneling, band discontinuity, and minority carrier lifetime. Our simulation results show that a maximum power conversion efficiency of ~15.5% can be obtained in a window of an optimum combination of bandgap and electron affinity of SnOx layer. Further enhancement in efficiency is achievable by improving the minority carrier lifetime. [ABSTRACT FROM AUTHOR]

The Si material is widely used by the manufacturers for sensing applications, because of its abundance. Better carrier sensing capability provide high performance. Solar cell is a sensor, which can sense the sun spectrum to convert it into electrical energy. This paper presents enhancement of passivation quality of GaInP/Si dual junction solar cell by enhancing the carrier transport through tunnel oxide. Reducing the SiO2 thickness increases the transport channel, thereby increasing the electric filed. This enhanced electric field accelerates the carrier transport in the passivation layer, and ultimately the passivation quality improves due to enhanced carries. The high electric field sensing accelerates the majority carriers towards the rear surface. Here, the improvement of the passivation quality is achieved via scaling down the oxide thickness as explained in the MIS tunneling theory. Reduction in oxide thickness provide more transport channels for the carriers, hence improves the tunneling process. Improved carrier sensing in 300nm-1100nm wavelength range, can progress towards the thermodynamic limit of open circuit voltage (${V}_{\textit {oc}}$). Also, we have used a wide-bandgap tunnel junction to electrically connect two cells, to see the effect on spectrum loss. The thickness and doping concentration of the tunnel junction plays very important role in tunneling process. Sharp edges and fast tunneling of the tunnel junction is the key element in proper current matching process. Numerical analysis of tunnel oxide thickness variation and wide-bandgap tunnel junction is done to obtain the optimum efficiency of 36.22% under 1-Sun concentration. [ABSTRACT FROM AUTHOR]

We have theoretically modeled ratchet-type intermediate band solar cells (IBSCs) and analyzed the effect of varying absorption coefficients on their performance. The main objective is to examine the impact of low absorptivity representing the low absorption of the practical nanostructured IBSCs. The devices are modeled using the detailed balance formalism at two bandgap combinations. Our results demonstrate that the introduction of small ratchet energy of 100 meV improves the efficiency of the IBSC. At one sun concentration, we show that using a ratchet mechanism provides steady enhancement over conventional IBSCs under different absorptivity. With an increase in light concentration, the performance of IBSCs with high absorptivity becomes close to the ratchet band solar cells (RBSCs). At the same time, the RBSCs continue to offer the enhancement at low absorptivity. These results show that the RBSCs at low to moderate sun concentration can provide promising results over the IBSCs even under low absorption conditions. [ABSTRACT FROM AUTHOR]

Quantum engineering in kesterite solar cells reveals a blending advancement keeping in mind that copper zinc tin sulfide (CZTS)-based material requires high-research implementation as a replacement for copper indium gallium selenide (CIGS) materials. In this article, quantum well-solar cells (QWSCs) on kesterite material is proposed in which CZTSxSe1−x and CZTS material is taken as well and barrier materials with different Sulfur (S) and Selenium (Se) content. All the optical, electrical, and material properties are investigated in detail to achieve high efficiency. The focus on the incorporation of a high number of quantum wells (QWs) (2 to 100 QWs) and performance analysis show the uniqueness of the study. Quantum efficiency (QE) of the solar cell with separate internal and external absorptions is also investigated here. Different issues on carrier propagation, recombination, and collection are emphasized to highlight the effect of carrier quantization in the material. A remarkable efficiency of 38% with 88% fill factor (FF) could be achieved from the broad range of the proposed structure, which may show a new path for next-generation solar cells. [ABSTRACT FROM AUTHOR]

Quantum engineering in kesterite solar cells reveals a blending advancement keeping in mind that copper–zinc–tin–sulfide (CZTS)-based material requires high-research implementation as a replacement for CIGS materials. In this article, a quantum-dot-embedded kesterite solar cell is proposed, in which CZTSx $\text{Se}1-_{x}$ and CZTS are taken as dot and barrier, respectively, with different sulfur (S) and selenium (Se) content. Focus is given on the incorporation of quantum dots (QDs) and a detailed investigation is carried out through optical and electrical performance, which shows the uniqueness of this study. Quantum efficiency of the solar cell with separate internal and external absorption is also investigated. Different issues on carrier propagation, recombination, and collection are emphasized to highlight the effect of carrier quantization in material. The reliability analysis of the solar cell is also a new scope to investigate the trap-assisted recombination. The detail analysis and remarkable efficiency may bring a new path for next-generation solar cells. [ABSTRACT FROM AUTHOR]

N-type ZnO top layer in view of improving the spectral response in the lower wavelength range (300–500 nm) has been integrated into the novel nanopillar-based n-CdS/p-CdTe solar cell. The device performance has been studied using physics-based device Simulator TCAD Silvaco. It has been found that integrated ZnO layer owing to its wide bandgap has not only improved the spectral response, and short circuit current density, but large valence band offset (VBO) energy ($\Delta {E}_{\text {v}} = 1$ eV) has also caused the increase in the open-circuit voltage (${V}_{\text {oc}}$) and efficiency ($\eta$) of the device. Besides, comparison of the device performance parameters such as short circuit current density (${J}_{\text {sc}}$), open-circuit voltage (${V}_{\text {oc}}$), and solar cell conversion efficiency ($\eta$) of the proposed device with its equivalent device structure without ZnO layer has shown the improvement by 13.96%, 3.09%, and 16.75%, respectively. Besides, added ZnO layer does not contribute to any series resistance leaving fill factor (FF) unaltered. [ABSTRACT FROM AUTHOR]

Back-contact modification using a 10-nm ZnS layer in CZTSSe-based solar cell can play a crucial role in improving photovoltaic conversion efficiency. An ultrathin layer of ZnS is deposited over Mo-coated soda lime glass substrate before depositing CZTSSe using sputtering. The crystal structure of deposited CZTSSe thin films over ZnS is recognized as (112)-oriented, polycrystalline in nature, and free from the presence of any secondary phases such as Cu2(S,Se) or Zn(S,Se). The bandgap of CZTSSe thin films deposited over ultrathin ZnS is observed to increase from 1.49 (deposited over Mo directly) to 1.58 eV at room temperature, as determined by spectroscopic ellipsometry. In addition, numerical simulation has been performed using SCAPS software. The impact of ZnS layer has been simulated by using the defects in the absorber and at the interface of ZnS/CZTSSe. The simulated results have been validated with experimentally fabricated CZTSSe device. Simulated device with ZnS intermediate layer is observed to give rise to a photovoltaic conversion efficiency of 15.2%. [ABSTRACT FROM AUTHOR]

In the increasingly rapid development of perovskite solar cells (PSCs), all-inorganic PSCs, especially Br-rich all-inorganic PSCs, not only inherit the advantages of an adjustable bandgap, and excellent light absorption, but also has superior stability. To find a simple-process and low-cost way to increase perovskite performance, we try to adjust the conduction band of CsPbIBr2 with the help of dipoles induced by PEI incorporating. Furthermore, we use carbon as the negative electrode to abandon the noble metal and hole transport layer (HTL). Finally, the solar cells with the structure of fluorine-doped tin oxide (FTO)/TiO2/CsPbIBr2/Carbon are prepared. The Voc and FF of the carbon-based, HTL-free and all-inorganic PSCs with polyethyleneimine (PEI) incorporating have an obvious improvement, and the champion device can get an efficiency of 7.5% with peak Voc of 1.2 V and maximum FF of 65%, which is far beyond the one without PEI incorporating. Our work hopes to give an effective method to produce a simple, cost-effective design for PSCs. [ABSTRACT FROM AUTHOR]

Research on photovoltaic solar cells has always been exciting due to its clean and green nature. However, the quest for alternative approaches to the design of highly efficient solar cells with optimal cost-efficiency ratios has also been progressing. CuSbS2-based ternary compound semiconductor is a promising candidate for the ultrathin film photovoltaic cell due to the high absorption coefficient, low cost, and earth abundant which makes it suitable to use as a thin-film absorber layer. The impact of various parameters such as thickness, bandgap, band alignment, temperature, carrier concentration, and bandgap grading has been studied to optimize the overall performance of the solar device. In present work, we have adopted the Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D) simulation approach to the design of CuSbS2 absorber-based solar heterostructure cells to boost the electrical properties of the solar cell. [ABSTRACT FROM AUTHOR]

In the endeavors to achieve lead-free perovskite solar cells, antimony-based hybrid materials have been identified as a promising alternative to toxic lead perovskite due to its stability and unique optoelectronic properties. In this study, we have presented a comprehensive analysis of MA3Sb2I9-based solar cells through device optimization. Various device parameters, such as active layer thickness, defect density, dopant concentration, interface defect density, and work function of the front contact electrode affecting the performance, have been rigorously investigated. By the optimized parameters, we achieved an open-circuit voltage (Voc) of 1.22 V, short-circuit current density (Jsc) of 31.79 mA/cm2, a fill factor (FF) of 50.82%, and a power conversion efficiency (PCE) of 19.79%. Furthermore, the addition of the tungsten disulfide (WS2) interlayer layer between the electron transport layer (ETL) and the active layer has been thoroughly studied, which enhances the PCE of the proposed device to 20.36%. This study indicates the great potential of the emerging lead-free perovskite solar cells and opens wide opportunities to design novel perovskite solar cells for broad photovoltaic applications. [ABSTRACT FROM AUTHOR]

With the perovskite-on-Si tandem solar technology at the onset of commercialization, it becomes imperative to tackle the toxicity concern of Pb in the perovskite structure. This study utilizes solar cell capacitance simulator (SCAPS) simulation software to investigate a tandem device with the crystalline Si (c-Si; bandgap: 1.12 eV) bottom cell in a mechanically stacked configuration with the stable and nontoxic CsSn0.5Ge0.5I3 (bandgap: 1.5 eV) as the top cell active layer. The device performance has been compared against that of a traditional tandem solar device setup utilizing MAPbI3 (bandgap: 1.55 eV) as the top cell active layer. Simulation results reveal power conversion efficiency (PCE) values of standalone CsSn0.5Ge0.5I3, MAPbI3, and c-Si cells to be 7.45%, 20.01%, and 25.95%, respectively, all in good agreement with published experimental results. The current matching condition between the top perovskite cell and the bottom c-Si cell has been probed through variation of perovskite layer thickness, yielding optimized thickness values for CsSn0.5Ge0.5I3 and MAPbI3 to be 365 and 225 nm, respectively. A tandem device with CsSn0.5Ge0.5I3-on-Si showcases a PCE of 28.53% (Voc : 1.72 V; Jsc : 20.02 mA/cm2; and FF: 83.74%) compared with an MAPbI3-on-Si device yielding a PCE of 32.29% (Voc : 1.88 V; Jsc : 19.969 mA/cm2; and FF: 85.99%). The results and analyses of this study highlight the feasibility of utilizing nontoxic materials, such as CsSn0.5Ge0.5I3, to attain high tandem device PCE values. [ABSTRACT FROM AUTHOR]

All-perovskite tandem solar cells have great potential to realize the efficiency beyond the Shockley–Queisser efficiency limitation of single junction solar cells. Here we investigate the photon redistribution effect induced by introduction of the optical coupling layer in two terminal (2 T) tandem solar cells. In this work, it is shown that the introduction of the optical coupling layer could not only reduce the reflection loss, but also would affect the redistribution of the absorbed photons in the tandem device due to the optical interference effect, which will disturb the previous balance and complicate the optical modulation. This photon redistribution phenomenon is systemically investigated by combining the optical and electrical aspects. By considering the coupling effect beyond the antireflection function after introducing the optical coupling layer, the new current match could be achieved, which would obviously improve the device performance further. Various materials such as LiF, MgF2, Al2O3, ZnO have been adopted as the optical coupling layer and it is demonstrated that this phenomenon is universal for all the cases. The improvement brought by photon redistribution effect may be even more obvious than antireflection function. Through analyzing the inner optical mechanism and modulating the structure, a higher performance can be achieved by carefully considering the optical coupling effect. [ABSTRACT FROM AUTHOR]

With the advancement of technology, highly efficient eco-friendly perovskite solar cells (PSCs) are desirable candidates for energy applications. In this article, we propose a design approach and potentiality of promising Pb-free PSC to analyze the different parameters. Different design strategies and factors such as defect density, characteristic decay energies, and capture cross section area have investigated using device simulation software. The defects in absorber layer are modeled by using exponentially decaying band tails for shallow-level defects and Gaussian distribution for the deep-level defects. By optimizing the device parameters, we have achieved a simulated conversion efficiency of 13.35% with open-circuit voltage (Voc) = 0.89 V, short circuit current density (Jsc) = 22.79 mA/cm2, and a fill factor (FF) = 65.28% under AM1.5G illumination. We have also studied the impact of absorber layer thickness and interface defect density on the performance of the solar cell. These simulation results can aid researchers in a reasonable choice of materials and optimally design high-performance PSC. [ABSTRACT FROM AUTHOR]

An irreversible model of the thermophotonic cell (TPC) with a heated forward-based light-emitting diode (LED) as an emitter and a photovoltaic cell (PVC) is established. The performances of the TPC are optimized and compared with those of the thermophotovoltaic cell (TPVC) based on finite-time thermodynamics. The results obtained show that there exist the optimally operating ranges of the voltages and band-gap energies of the LED and PVC. The thermal flow emitted from the heated LED dramatically exceeds that from the pure thermal emitter. The maximum efficiency of the TPC is less than that of the TPVC, whereas the maximum power density of the TPC surpasses that of the TPVC under an arbitrary emitter temperature. The TPC has the advantages of the relatively high optimal band-gap energies and relatively low-operating temperatures so that it is easier to be made than the TPVC. [ABSTRACT FROM AUTHOR]

The effectiveness of the mesoporous TiO2 layer, which acts as an active n-type semiconductor layer in dye-sensitized solar cells (DSSCs), was investigated by varying AgVO3 doping. To optimize the meso-superstructure, the doping concentration was varied from 0% to 25% using experimentally validated simulations. Moreover, performance comparisons between the experimentally fabricated DSSCs based on natural beetroot dye and the commonly used N719 dye were made. A 15% doping concentration was found optimum for our DSSC, which delivered an output power of 19.24 mW, 6.1% power conversion efficiency, and an open-circuit voltage, ${V}_{\text {oc}}$ , of 0.5 V and a short-circuit current density, ${J}_{\text {sc}}$ , of 21 mA/cm2 in diffused light conditions. Based on these performance results, we integrated our optimized DSSC in an underwater sensing unit as a light harvester. [ABSTRACT FROM AUTHOR]

An analytical study has been carried out to obtain the device performance parameters of InGaN/GaN-based multiple quantum well solar cell (MQWSC). Significant improvements are made upon the preexisting models reported in the literature for predicting device performance matrix for MQWSC. The American Society for Testing and Materials (ASTM) standards data sheets are utilized for attaining photon flux density instead of blackbody radiation formula. Furthermore, the photon flux density is utilized to evaluate the performance parameters of MQWSC and bulk p-i-n solar cell. Results suggest that by incorporating QWs in the intrinsic region (${x} = {0.1}$ in $\text{In}_{x}\text{Ga}_{{1}-{x}}\text{N}$), ∼27% increment in the conversion efficiency can be achieved as compared to that from the bulk solar cell. Moreover, the impact of operating temperature in the solar cell performance is also studied. The rise in temperature leads to an increase in short-circuit current density; however, open-circuit voltage and conversion efficiency decrease. A decrement of ∼9.7% in the conversion efficiency of MQWSC is observed with the rise in temperature from 200 to 400 K as compared to ∼11.6% decline in p-i-n solar cell. [ABSTRACT FROM AUTHOR]

Thermoradiative cells provide a means of electricity generation through direct transfer of energy from heat flux at the cell to radiation from the cell to a colder ambient. While thermodynamic limits and detailed models have been developed for thermoradiative cells, intuitive models to guide the development of thermoradiative cells and associated circuits have not been established. This work presents an equivalent circuit model for thermoradiative cells based on the underlying thermodynamic device description and incorporation of parasitic nonradiative processes. The compact model combines common circuit elements and defines the specific quantitative parameters needed to describe the behavior of these devices, serving as an important tool for the development of thermoradiative energy devices and circuits. [ABSTRACT FROM AUTHOR]

A novel architecture of cell structure tailored to ultra-high (>2000 suns) concentration ratios is proposed. The basic solar cell consists of two p-n junctions connected in series by a highly doped tunnel diode with the metallic contacts located laterally. The tunneling connection allows using direct band-gap semiconductor compounds aiming to optimize the absorption of the spectrum. The performance of the novel architecture is investigated up to ultra-high concentration using TCAD software. Simulations show its viability for developing a new generation of solar cells to increase the potential in terms of efficiency and cost reduction of ultra-high concentrator systems. The solar cell does not show any degradation with concentration and efficiency as high as 28.4% at 15000 suns has been obtained for a preliminary design. [ABSTRACT FROM AUTHOR]

A new model of the intermediate band thermoradiative cell (IBTRC) is put forward. Expressions for the power output density (POD) and efficiency of the IBTRC are derived. The current densities and PODs arising from the normal transitions and interband transitions of electrons are compared. It is found that when the IBTRC with a bandgap of 0.2 eV is operated between the heat source at 1000 K and the surroundings at 300 K, the maximum POD and efficiency of the cell are approximately $1.583\times $ and $1.096\times $ of those of the thermoradiative cell without intermediate bands (IBs) under the same operating temperature and bandgap, respectively. This shows that the performance of the IBTRC can be largely improved by the insert of the IB. Moreover, the optimal selection criteria of some key parameters are provided, and then the optimum operating conditions of the IBTRC are determined. Finally, several issues that will influence the performances of the IBTRC are pointed out. These results may help engineers to fabricate high-performance IBTRCs. [ABSTRACT FROM AUTHOR]

In this study, we have proposed an optical broadband angular reflector having a band selective feature and high reflectivity rate for photovoltaic implementations by using a photonic crystal structure made of two different dielectric layers. This paper presents new and useful information about a reflector that was designed by using a periodic structure composed of two Si based layers for the visible range in the solar spectrum region. The system has been adjusted in such a way that it could cover a wide wavelength area between the photonic band gaps at nearly λ ≈ 300-800 nm. We have tested the proposed reflector against different angles of incidence of the light. The reflectivity spectra of the optical structure have been calculated. [ABSTRACT FROM AUTHOR]

An analytic expression for the JV-characteristic of intermediate band (IB) solar cells with overlapping absorption coefficients is derived. The characteristic contains six voltage-independent parameters that are calculated from material properties, cell properties, and external conditions. Combined with exponential functions containing the cell voltage, these describe the full JV-characteristic. Expressions are also derived for the short-circuit current and open-circuit voltage. The model represents a major simplification compared with the existing model for this type of devices. The simplicity will facilitate the understanding of the operation of such cells. Furthermore, the computation time required when modeling IB solar cells with overlapping absorption coefficients can be shortened considerably. The model also facilitates the incorporation of light trapping schemes. Light trapping with Lambertian surfaces is used as an example. [ABSTRACT FROM AUTHOR]

We studied the miniband dependence on the structural parameters and shape in type-II multilayer germanium (Ge)/silicon (Si) quantum dot superlattice (QDSL) solar cell. A maximum tunable range of ground-state energy is 19% by tuning layer distance down to 0.5 nm, whereas 24.5% is achieved by adjusting the horizontal dot-to-dot spacing down to 0.3 nm. The reduction of effective bandgap is severe for cylindrical QDs than ellipsoidal and conical QDs in the ultradense QDSL, thus leading to a relatively lower conversion efficiency. On average, the thickness of QD shows a negative correlation to conversion efficiency. We observed a high conversion efficiency of 27.22% in a bilayer conical QDSL under an AM1.5 spectral irradiance and one sun illumination. [ABSTRACT FROM AUTHOR]

Based on the near-field (NF) model of a thermophotovoltaic cell (TPVC) consisting of an emitter and a photovoltaic (PV) cell separated by a vacuum gap, two important formulas for the power output and efficiency are analytically derived by using fluctuation electrodynamics theory. The general performance characteristics of the NF-TPVC are evaluated. The optimum choice criteria of several key parameters, such as the power output density, efficiency, and distance of the vacuum gap of the TPVC, the current density and voltage output of the PV cell, and the band-gap of semiconductor materials in the PV cell, are supplied. Moreover, the maximum power output densities and efficiencies of three NF-TPVCs made of InSb, InAs, and InGaAsSb are calculated and the corresponding optimum values of other parameters are determined. The results obtained may provide some theoretical guidance for engineers to optimally design NF-TPVCs. [ABSTRACT FROM PUBLISHER]

The effect of nitrogen insertion in a benzothiadiazole (BT) moiety was investigated via the synthesis of a novel copolymer based on dithienosilole (DTS) and pyridalthiadiazole (PT), the heterocyclic counterpart. Stille cross coupling of the electron rich and electron poor units yields poly[(4, 4’-didodecyldithieno[3, 2-b:2’, 3’-d]silole-2, 6-diyl)-alt-(2, 1, 3-pyridalthiadiazole-4, 7-diyl), a nonsoluble polymer. Dense π–π stacking interactions that inhibited polymer solubility were cured by the introduction of two solubilizing hexylthiophene spacers, and a new soluble low-bandgap copolymer, namely poly[(4, 4’-didodecyldithieno[3, 2-b:2’, 3’-d]silole-2, 6-diyl)-alt-4, 7-bis[2-(3-hexyl)thienyl]-2, 1, 3-pyridalthiadiazole-5, 5’-diyl] (PDTSDTPT), was alternatively obtained. For reasons of comparison, the corresponding oligomer, i.e., ODTSDTPT, was also synthesized. Their chemical, thermal, optical, electrical, and electrochemical properties were investigated. UV–visible spectroscopy revealed that PDTSDTPT alternating copolymer is more absorbing than its BT analog. It has a lower optical bandgap, higher absorptivity, and red-shifted absorption spectrum into the near-infrared region up to 900 nm. Photovoltaic applicability was investigated for PDTSDTPT and its derived oligomer in bulk heterojunction solar cells employing PC 60BM, [6,6]-phenyl-C60 butyric acid methyl ester, as the n-type semiconductor. Significant improvement of open-circuit voltage was evidenced with PT-based materials. The short-circuit current (J SC) and fill factor (FF), however, remain a material of continuous improvement by morphology control. [ABSTRACT FROM PUBLISHER]

This paper conceptualizes vertical junction, graded bandgap AlfGa1–fAs rectangular-slab and cylindrical solar cells. The cells are analyzed through numerical modeling under drift-diffusion transport framework. We find that, these special cells can significantly increase photo-current density due to asymmetry between light receiving and electrical contact areas, while at the same time bandgap grading within quasi-neutral regions enables both near band edge and short wavelength absorption. Under AM 1.5G, 1000-W/ \textm^2 illumination to the light receiving area (hence, electrical contacts receive 32 sun power during actual photo conversion), we find that rectangular-slab cells can outperform cylindrical cells of identical dimension and exhibit maximum 529.8 mA/cm2 short circuit current density, 1 V open circuit voltage and 0.88 fill factor when maximum aluminum mole fraction is fixed at 0.175, and band gap grading is fixed within 15.24 and 3.81~\mu \textm from respective depletion edges (p and n). Furthermore, we find that through a combination of bandgap grading and mole fraction tailoring, maximum 4.91\times 10^4 and 1.96\times 10^5 V/m (p and n) built-in fields can be achieved, when bandgap grading is made in 0.05- and 0.2-eV/ \mu \textm (p and n) steepness, which results in 46.8 percent efficiency in graded rectangular-slab cells [ABSTRACT FROM AUTHOR]

The ideal diode equation is regularly used to describe the \textit JV -characteristic of single junction solar cells. The connection between the diode equation and fundamental physics is the application of the Boltzmann approximation to describe the fluxes of photons emitted by the cell. In this paper, this approximation is used to derive analytic \textit JV -characteristics for three photovoltaic high-efficiency concepts, intermediate band solar cells, and solar cells optically coupled to up and downconverters. These three concepts share the common feature that they allow excitation of electrons between at least three energy levels, which assures a better utilization of the solar spectrum and leads to limiting efficiencies surpassing the Shockley–Queisser limit. Although being considerablysimpler to implementand use, the resulting \textit JV -characteristics reproduce the limiting efficiencies obtained from full detailed balancemodels. The simplicity facilitates the intuitive understanding of such devices. The presented models also have the potential to serve as a useful framework for further modeling, through savings in computation time and complexity. [ABSTRACT FROM PUBLISHER]

The peculiar nature of light-matter interaction in atomically thin transition metal dichalcogenides is recently under examination for application in novel optoelectronic devices. Here, we show that heterostructures composed of two or more such layers can be used for solar energy harvesting. The strong absorption in these atomically thin layers makes it possible to achieve an efficient power conversion with a minimal amount of active material. We describe in detail two different fabrication techniques that allow to realize heterostructures with clean, atomically sharp interfaces. The observed electrical and photovoltaic properties are analyzed. Our findings suggest that, accompanied by the advances in large area fabrication of atomically thin transition metal dichalcogenides, van der Waals heterostructures are promising candidates for a new generation of excitonic solar cells. [ABSTRACT FROM PUBLISHER]

GaInAsSb cells may show better performance than GaSb cells in low-temperature thermophotovoltaic systems due to their lower bandgap energies. In this paper, numerical simulation is used to evaluate GaInAsSb and GaSb cells with similar structures under different radiation temperatures. We find that GaInAsSb cells with n-type emitters show slightly higher output power densities compared with those for GaSb cells with n-type emitters below 1500 K given-blackbody radiation, but the power density of the GaSb cells will surpass the former’s above this temperature point. Furthermore, over the temperature range of $1200\sim 2000$ K, the efficiencies of GaSb cells with n-emitters are $1.31\sim 2.32$ times higher than those of GaInAsSb cells with n-emitters if filters with 10% subbandgap losses are used. Several parameters that affect the GaInAsSb cell were analyzed, such as doping profiles, thicknesses of GaInAsSb epitaxial layer and surface recombination velocity. The n-on-p junctions, i.e., n-type emitters vs p-type emitters are better for GaInAsSb cell fabrication, which is similar to that for the GaSb cell. [ABSTRACT FROM AUTHOR]

Carrier-selective contacts based on thin oxides of nickel and titanium are computationally investigated for heterojunction silicon solar cells. Replacing the standard amorphous/c-Si heterojunction with NiO/c-Si (front) and TiO2/c-Si (back), we explore the physical requirements to enhance the cell efficiency beyond the physical limits of the conventional structure. Under ideal conditions, a wider bandgap (>3 eV) of these metal oxides provides a high optical transparency, whereas a near-perfect alignment of their energy bands with silicon ensures a high fill factor (FF), which is often difficult to obtain in some of the other wide-bandgap alternatives, e.g., SiOx, due to imperfect band offsets that hinder carrier extraction. We explore the practical nonidealities that could possibly degrade cell efficiency below its ideal limit. In particular, effects of interfacial defects, Fermi-level pinning at c-Si/TiO2/metal contact, variability in the bandgap of NiO, and nonoptimized metal oxide doping density are investigated quantitatively. Using the reported experimental data for these nonideal effects, we highlight that the cell efficiency of \sim 28 % could be achieved under AM1.5 illumination with an optimal cell design. These modeling insights provide useful guidelines for the future development of exploratory window layers for silicon solar cells using NiO (front) and TiO2 (back) heterojunctions. [ABSTRACT FROM AUTHOR]

The organic-metal halide perovskite solar cells have recently shown the high power conversion efficiency (PCE) exceeding 20%. A better understanding of the relationships between material parameters, device architectures, and performance is still required for the continued development of the perovskite solar cells. Three types of architectures are simulated with the program 1-D device simulation program for the analysis of microelectronic and photonic structure. The hole transport material-free MAPbI3 solar cells attain the simulated PCE of 24.1%. A maximum PCE of 26.60% and a maximum V\mathrm {OC} (open-circuit voltage) of 1.83 V for FTO/ZnO/MAPbX3 ( X = I and Br)/CuSCN/Au-based solar cells are predicted, respectively. The FTO/ZnO/MAPbI3/MAPbBr3/CuSCN/Au-based solar cells first designed possesses a characteristic of tunable PCE and V\mathrm {OC} by changing the thicknesses of MAPbI3 and MAPbBr3, and the PCE of 27.50% ( J_{\mathrm {SC}} = 26.17 mA/cm2, V\mathrm {OC} = 1.19 V, and \textrm {FF} = 0.88 ) was obtained. These simulation results can help researchers to reasonably choose materials and optimally design high-performance perovskite solar cells. [ABSTRACT FROM AUTHOR]

We present the electronic properties of the crystalline-silicon (c-Si)/SiO2/am-Al2O3 interface using first principles calculations. First, we generate a relaxed $3\,\times \,1$ supercell of amorphous (am)-Al2O3, which we use as a benchmark structure, validated through the experimental data. Next, using this, we generate a relaxed supercell of the c-Si/am-Al2O3 interface with a thin layer of SiO2 sandwiched between them. With this structure, we demonstrate that at the interface section, the percentage of the tetrahedral coordinated Al atoms decreases while that of the octahedral coordinated Al atoms increases compared with the Al atoms present in the bulk section of the interface structure. In addition, on an average, the effective charges on Al atoms increase by 0.19|e|, while for O atoms, the effective charges decrease by 0.02|e|. This change in the bonding distribution and charges near the interface might be responsible for the occurrence of negative fixed charges, also confirmed by various experiments involving am-Al2O3 passivation in Si-based solar cells. The origin of these negative charges on the other hand is under discussion and speculation. [ABSTRACT FROM AUTHOR]

Effort to improve the bulk heterojunction organic solar cells’ absorption efficiency utilizes tandem structures combining low- and high-bandgap absorbing polymers so that a broader spectrum of sunlight's energy can be used for the photon-to-electron conversion and the thermalization loss of photon energy can be reduced. However, at the intersection of the upper energy level of the high-bandgap polymer and the lower energy level of the low-bandgap polymer, photon absorption efficiency remains low due to the destructive interference of these energy states at the band edges. In order to circumvent this issue, we theoretically propose using dielectric fiber arrays to generate lensing effects atop of a thin-film polymer/organic tandem solar cell (OTSC), aiming to enhance its optical absorption efficiency. Dielectric fibers have been calibrated to generate the optimal antireflection coating resulting in an integrated absorption enhancement up to 11% compared to its flat-OTSC counterpart. The overall integrated AM1.5 G (air mass 1.5 global simulated solar spectra) absorption yields absorption efficiencies of 83% in an optimal configuration, with a cell size of 600 nm and fiber radius of 150 nm. By using fibers as focusing lenses/antireflectors, we demonstrate that there exists zero reflection at multiple visible frequencies, leading to a relative broadband absorption of an ultrathin substrate. [ABSTRACT FROM PUBLISHER]

Within the envelop-function framework, we propose a more efficient finite-element method to calculate the miniband structure and density of states in an idealistic nanocrystal array with realistic geometrical parameters. This method clearly reveals the miniband formation and accurately calculates the energy dispersion relationship. The calculated result agrees well with the analytical Kronig-Penney method. More importantly, this method surmounts the theoretical approximations of the multidimensional Kronig-Penney method, and provides significant information for 3-D quantum dots solar cell design by simulating an in-plane germanium nanodisk array in bulk silicon. [ABSTRACT FROM AUTHOR]