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As the balance of system cost of photovoltaic (PV) installations governs the competitiveness of PV device market, next‐generation solar cells desire substantially enhanced power conversion efficiencies (PCEs). The single‐junction perovskite and Si solar cells have demonstrated PCEs beyond 26% and 25%, respectively. The tandem configuration has crossed the threshold posed by the shockley queisser limit by demonstrating the 33.9% PCE. However, the unresolved issues in the perovskite community from a stability perspective pose challenges for realizing highly efficient and stable perovskite–Si tandem solar cells (TSCs). This review highlights the current status of perovskite–Si TSC from a stability perspective besides elucidating the degradation mechanisms at the perovskite–Si at the cell and module level. A highly efficient perovskite–Si TSC needs optimization keeping view the specific requirements for tandem configuration like strain, current matching, and bandgap optimization between the top perovskite and bottom Si subcell. Various stressors affecting the efficiency of the perovskite–Si module, namely, reverse bias and hot spot formation, and delamination, highlight valuable insight to develop future strategies for the perovskite–Si TSC. Stability regimes for the single‐junction perovskite solar cell can provide the essential stepping stone but, modified stability regimes are inevitable. [ABSTRACT FROM AUTHOR]

The procedures for the power rating of tandem‐cell‐based concentrator photovoltaic (CPV) modules defined in the international standard IEC 62670‐3 are adapted to the requirements of tandem‐cell‐based flat plate PV modules. The adjusted procedure describes how to translate outdoor measured PV current–voltage characteristics to standard test conditions (STC): 1000 W/m, 25°C cell temperature, AM1.5g spectral conditions. In this work, we describe how to obtain all required input parameters: thermal transient measurements to determine the module temperature coefficients, categorizing and filtering the prevailing spectral irradiance conditions using spectral matching ratios, and determining the 25°C module open‐circuit voltage from dark current–voltage curves. Three specimen PV modules (triple‐junction, III‐V on Silicon and III‐V on Germanium) have been measured for several months outdoors on a dual axis tracking unit at Fraunhofer ISE in Freiburg. In this work, we demonstrate that the CPV module power rating procedures in IEC 62670‐3 are also—in a modified form—to be recommended for the outdoor rating of tandem‐cell‐based flat plate PV modules. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting, and carbon dioxide (CO 2) utilization devices have attracted immense attention as sustainable technologies for the generation of hydrogen (H 2) fuel and value-added chemicals feedstock. Among numerous semiconductors, bismuth vanadate (BiVO 4) has emerged as a promising photoanode owing to its fascinating features such as high chemical stability, straddling band alignment with water redox levels, eco-friendly, and cost-effectiveness. However, sluggish oxidation kinetics, photo-corrosive nature, low electronic conductivity, and short carrier diffusion length limit its commercialization on the PEC horizon. To mitigate these inadequacies, several strategies have emerged such as novel heterojunctions, doping with unique materials, interface modulation, morphology, facet orientation, co-catalyst loading for surface engineering, etc. to realize the outstanding cost-to-efficiency ratios and long-term stability of PEC devices. The review highlights the recent advancement in BiVO 4 -based photoanodes in last five years (2018–2022) and their utilization in the single absorber and unexplored tandem PEC systems towards boosted water splitting and CO 2 reduction. A discussion on theoretical studies of BiVO 4 -based PEC systems elucidates the microscopic mechanism of promotion effect of the bulk/interface/surface strategies on surface catalysis as well as interfacial charge transfer in boosting oxidation kinetics. Moreover, this review addresses the versatility of the BiVO 4 -based photoanode for the novel yet commercially viable PEC applications. This review will provide a broad avenue in designing highly durable, and scalable BiVO 4 -based systems toward various PEC energy conversion devices. [Display omitted] • BiVO 4 is a promising photoanode for PEC water splitting and CO 2 reduction. • Recent progress in the various strategies to improve PEC performance is reviewed. • BiVO 4 -based tandem water splitting and CO 2 reduction systems are emphasized. • Future outlooks are addressed with associated challenges. [ABSTRACT FROM AUTHOR]

With the success of silicon (Si) solar cell technology, research and development on higher efficiency multijunction solar cells is gaining much attention. Tandem cells with a perovskite top cell and a Si bottom cell show particular potential. However, the optical modeling of such devices is complicated by the broad range of length scales involved; the optically thin layers and nanoscale features of a perovskite solar cell require some version of wave optics or even full field electromagnetic (EM) calculations, while the micrometer scale structuring and large dimensions of Si cells are much more manageable using geometrical (ray) optics. In the present work, a method for combining EM and ray optical calculations is developed and described in detail, with examples provided in the software Comsol Multiphysics. For regions with thin films or nanoscale features, EM wave calculations are performed using the finite element method. These calculations provide the phase and amplitude of the waves diffracted into different orders, of which only the regular reflection and transmission are typically of relevance for nanoscale periodicity. In the ray optics simulation, the corresponding regions are implemented as diffracting interfaces, with deterministic transformations of the Stokes vector components according to the EM wave calculations. Meanwhile, the absorbed intensity of intersecting rays is recorded. The method is applied to separate perovskite and Si solar cells and to a few tandem solar cells of relevance for two- versus four-terminal configurations. Corrections for strongly absorbing media in the ray tracing algorithm, which use generalized versions of the Fresnel coefficients, Snell's law and the Beer-Lambert law, are also evaluated. In a typical Si solar cell with a front surface structure of inverted pyramids, such corrections are found to reduce the absorption by up to 0.5 percentage units compared to a conventional ray tracing calculation. The difference is concluded to originate mainly from reduced absorption rates of inhomogeneous waves, rather than from enhanced escape probabilities for (quasi-) trapped rays at the Si front surface. The method is further applied to evaluate the effects of a plasmonic nanoparticle array, embedded in a perovskite solar cell stack that is located directly on the microstructured Si surface. [ABSTRACT FROM AUTHOR]

As perovskite photovoltaics (PV) advance from the laboratory to commercial prototypes, their accurate and reliable performance testing is becoming increasingly important. The well‐documented dynamic response of perovskite solar cells to an external applied voltage has led to the development of steady‐state performance measurement methods; however, these methods have not been widely adopted by the perovskite PV community. A key reason for this is that steady‐state measurement methods take tens of minutes to complete, as opposed to conventional "fast" current–voltage (I–V) measurements usually lasting a few seconds. Fast I–Vs arise from a snapshot, almost always not a steady‐state condition of the device; however, given their widespread use, the question arises: how do performance parameters of perovskite PV compare when measured with fast I–V and with a steady‐state method? Results compiled from approximately 200 perovskite PV cells, including single junction, and two‐terminal perovskite–perovskite and perovskite–Si tandems, show that fast I–Vs can provide a useful measure of the open‐circuit voltage of the devices, while the short‐circuit current and the overall efficiency can be widely misestimated. The implications of these findings on performance testing protocols are discussed and possible options for fast and accurate testing of perovskite PV are proposed. [ABSTRACT FROM AUTHOR]

The development of an efficient conversion system to transform solar energy into chemical energy, such as renewable hydrogen, is a promising way to overcome energy problems. Photoelectrochemical (PEC) water splitting is a promising means of obtaining renewable hydrogen directly from water utilizing sunlight. Recent reports have demonstrated that a PEC cell with a tandem configuration (tandem cell) has the potential to realize a high solar‐to‐hydrogen (STH) energy conversion efficiency by solar water splitting. However, there are still many obstacles to the development of practical and cost‐effective tandem cells. In particular, development of efficient photoanodes for the oxygen evolution reaction (OER) is a prerequisite for improving the STH efficiency. Herein, recent progress in developing (semi)transparent photoanodes for the OER, such as Fe2O3, BiVO4, and Ta3N5, is described based on the topics of preparation methods, semiconductor properties, and PEC performance. In addition, the strategies for enhancing the STH efficiency of tandem cells consisting of (semi)transparent photoanodes conjugated with photovoltaic (PV)‐based cathodes are summarized. This Review is expected to provide guidelines for the future development of tandem cells capable of highly efficient and stable water splitting.

• A first working monolithic CZTS/Si tandem cell is presented and characterized. • A MoS 2 /FTO/ZnO intermediate contact between top and bottom cells is developed. • Limiting factors of this device are addressed and investigated to overcome them. Earth abundant Cu 2 ZnSnS 4 (CZTS) semiconductor can find a promising application as wide-bandgap top cell absorber in CZTS/Silicon tandem devices. The coupling between the top and the bottom cells in a monolithic device requires the development of a proper intermediate connection able to ensure: (i) high transparency in the infrared region (ii) good electric contacts and (iii) good chemical stability under thermal treatments used for the CZTS growth, in order to prevent elements interdiffusion and silicon degradation. To this purpose, some multilayered structures based on MoS 2 and different Transparent Conductive Oxides (TCOs) were tested as intermediate connection in CZTS/Silicon tandem devices. The first working monolithic tandem cell, with open circuit voltage of about 950 mV and an efficiency of 3.5%, was obtained using a MoS 2 /FTO/ZnO trilayer structure as intermediate contact between the top and the bottom cells. Some limiting factors of this device were addressed and investigated in order to increase the tandem cell efficiency. [ABSTRACT FROM AUTHOR]

A series of zinc tetraphenylporphyrin photosensitizers furnished with three different anchoring groups, benzoic acid, phenylphosphonate and coumarin-3-carboxylic acid, were prepared using 'click' methodology. All three gave modest performances in liquid junction devices with I3–/I– as the electrolyte. The distinct spectroscopic properties of the porphyrins allowed a detailed investigation of the adsorption behaviour and kinetics for charge transfer at the NiO‖porphyrin interface. The adsorption behaviour was modelled using the Langmuir isotherm model and the phosphonate anchoring group was found to have the highest affinity for NiO (6.65 × 104 M−1) and the fastest rate of adsorption (2.46 × 107 cm2 mol−1 min−1). The photocurrent of the p-type dye-sensitized solar cells increased with increasing dye loading and corresponding light harvesting efficiency of the electrodes. Coordinating the zinc to a pyridyl-functionalized fullerene (C60PPy) extended the charge-separated state lifetime from ca 200 ps to 4 ns and a positive improvement in the absorbed photon to current conversion efficiency was observed. Finally, we confirmed the viability of electron transfer from the appended C60PPy to phenyl-C61-butyric acid methyl ester, a typical electron transporting layer in organic photovoltaics. This has implications for assembling efficient solid-state tandem solar cells in the future. This article is part of a discussion meeting issue 'Energy materials for a low carbon future'. [ABSTRACT FROM AUTHOR]

Over recent decades, the possibility of using solar power as an energy source has been limited by the implementation costs and the net conversion efficiency. Additionally, in comparison with the traditional sources, solar energy cannot produce energy for all the twentyfour hours of the day, which increases the costs of the source, due to the need of a backup system. Therefore, this paper studies the effect of combining different types of semiconductors as Si, Ge, AlGaAs and GaAs, focusing on how the conversion efficiency can be improved. In order to perform this, a multilayer solar cells analysis across the study of the quantum efficiency, which quantifies the amount of energy lost in the power conversion process, is implemented. In order to develop the required study PC1D software, specialized in simulate semiconductor's behavior based on its physiochemical properties, which gives the possibility to create different layers of solar cells is utilized. From the data acquired of the simulated cells, the paper presents the electrical results starting from a cell of one layer to a cell of four layers with the aim of establishing the relation between the number of layers and the net conversion efficiency under standard environmental conditions. [ABSTRACT FROM AUTHOR]

Fabrication of wide band-gap ( E g ) CuGaSe 2 (CGSe) thin film solar cells with large area uniformity and good reproducibility is difficult, which is crucial for tandem cells. In this work, a method was proposed and investigated to overcome this problem. CGSe solar cells were fabricated by sputtering from a ternary CGSe target and post selenization treatment at different temperatures. After selenization, the CGSe grains grow up gradually, and the copper-poor and selenium-rich CGSe absorbers are obtained successfully. The X-ray diffraction peaks are all corresponded to CGSe phase. As the temperature increases from 530 to 570 °C, the average efficiency increases from 1.57% to 3.11%. When the temperature reaches 590 °C, the efficiency drops to 2.38%. The champion device obtained at 570 °C shows an E g of 1.66 eV and an efficiency of 3.21%, which indicates the potential for the top cell in tandem solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Using dual‐photoelectrode photoelectrochemical (PEC) devices based on earth‐abundant metal oxides for unbiased water splitting is an attractive means of producing green H2 fuel, but is challenging, owing to low photovoltages generated by PEC cells. This problem can be solved by coupling n‐type BiVO4 with n‐type Bi4V2O11 to create a virtual p/n junction due to the formation of a hole‐inversion layer at the semiconductor interface. Thus, photoelectrodes with high photovoltage outputs were synthesized. The photoelectrodes exhibited features of p‐ and n‐type semiconductors when illuminated under an applied bias, suggesting their use as photoanode and photocathode in a dual‐photoelectrode PEC cell. This concept was proved by connecting a 1 mol % W‐doped BiVO4/Bi4V2O11 photoanode with an undoped BiVO4/Bi4V2O11 photocathode, which produced a high photovoltage of 1.54 V, sufficient to drive stand‐alone water splitting with 0.95 % efficiency. [ABSTRACT FROM AUTHOR]

We report the synthesis of three new push-pull dyes specially designed for the sensitization of mesoporous p type semi-conductor NiO for the construction of p type dye sensitized solar cells (pDSC). Their structure stems from the conjugation of the well-known tris(carboxy-arlyamine) anchoring moiety to a benzothiadiazole acceptor through a fluorene ( PP1 ) or thiophene-fluorene linker ( PP2 ). Appending a NDI secondary acceptor onto PP2 yielded a dyad ( PP2-NDI ). The push-pull structure is here particularly adapted to the sensitization of p-type semi-conducting materials. All three dyes were investigated by spectroscopic and electrochemical techniques, and their electronic properties were modelled by TD-DFT. In all cases, the new sensitizers exhibit adequate absorption features (spanning from 400 nm to 600 nm, extinction coefficients between 20000 and 27000 M −1 cm −1 ) and their thermodynamic parameters are all in favor of efficient interfacial charge transfers involving NiO. pDSC were constructed with all three dyes; high photoconversion efficiencies (PCE) were reached, especially in the case of dyad PP2-NDI (Jsc = 5.90 mA/cm 2 , Voc = 143 mV, FF = 33.8%, PCE = 0.29%), due to a combination of outstanding electronic properties and increased charge separation state lifetime. Tandem DSC (tDSC) composed of a TiO 2 photoanode sensitized by the dye D35 and a NiO photocathode sensitized by PP2-NDI were assembled with two different electrolytes (I 3 − /I − or T 2 /T − based electrolytes). The latter gave PCE among the best ever reported for tDSC (Jsc = 5.90 mA/cm 2 ; Voc = 896 mV; FF = 63%, PCE = 2.80% in the case of the I 3 − /I − electrolyte, Jsc = 4.52 mA/cm 2 , Voc = 840 mV, FF = 60% and PCE = 2.27% for T 2 /T − based devices) unraveling the significance of the new dyes presented in this study. [ABSTRACT FROM AUTHOR]

Tandem photoelectrochemical water splitting cells utilizing crystalline Si and metal oxide photoabsorbers are promising for low-cost solar hydrogen production. This study presents a device design and a scalable fabrication scheme for a tandem heterostructure photoanode: p+n black silicon (Si)/SnO2 interface/W-doped bismuth vanadate (BiVO4)/cobalt phosphate (CoPi) catalyst. The black-Si not only provides a substantial photovoltage of 550 mV, but it also serves as a conductive scaffold to decrease charge transport pathlengths within the W-doped BiVO4 shell. When coupled with cobalt phosphide (CoP) nanoparticles as hydrogen evolution catalysts, the device demonstrates spontaneous water splitting without employing any precious metals, achieving an average solar-to-hydrogen efficiency of 0.45% over the course of an hour at pH 7. This fabrication scheme offers the modularity to optimize individual cell components, e.g., Si nanowire dimensions and metal oxide film thickness, involving steps that are compatible with fabricating monolithic devices. This design is general in nature and can be readily adapted to novel, higher performance semiconducting materials beyond BiVO4 as they become available, which will accelerate the process of device realization. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting, which is a type of artificial photosynthesis, is a sustainable way of converting solar energy into chemical energy. The water oxidation half-reaction has always represented the bottleneck of this process because of the thermodynamic and kinetic challenges that are involved. Several materials have been explored and studied to address the issues pertaining to solar water oxidation. Significant advances have recently been made in the use of stable and relatively cheap metal oxides, i.e., semiconducting photocatalysts. The use of BiVO4 for this purpose can be considered advantageous because this catalyst is able to absorb a substantial portion of the solar spectrum and has favourable conduction and valence band edge positions. However, BiVO4 is also associated with poor electron mobility and slow water oxidation kinetics and these are the problems that are currently being investigated in the ongoing research in this field. This review focuses on the most recent advances in the best-performing BiVO4-based photoanodes to date. It summarizes the critical parameters that contribute to the performance of these photoanodes, and highlights so far unresolved critical features related to the scale-up of a BiVO4-based PEC water-splitting device. [ABSTRACT FROM AUTHOR]

A photoelectrochemical (PEC) cell composed of a WO 3 /dye-sensitized solar cell (WO 3 /DSSC) and copper oxide (Cu x O, where x =1 and 2) wire arrays as a dual-absorber photoanode and cathode, respectively, is demonstrated as a stand-alone, durable device for CO 2 photoconversion. The Cu x O wire arrays, which have high surface-to-volume ratios, exhibit promising electrocatalytic activity for CO 2 conversion to CO at Faradaic efficiencies of ~80% and ~60% at E=−0.2 and −0.4 V vs . RHE, respectively, and H 2 production is minimized at a Faradaic efficiency <~20% in the potential range between −0.2 and −1.0 V vs . RHE. The single-absorber cell of a WO 3 photoanode and Cu x O wire array cathode couple (WO 3 -Cu x O) requires a minimum overpotential of ~0.7 V to drive CO 2 conversion. For stand-alone CO 2 conversion, a DSSC is coupled to the WO 3 -Cu x O system. In the dual-absorber cell (WO 3 /DSSC-Cu x O), the long-wave band (λ > ca . 450 nm) passed through the semitransparent WO 3 film is absorbed by the dye-sensitized TiO 2 electrode of the DSSC. The WO 3 /DSSC-Cu x O shows a potential gain of ~0.7 V and is able to successfully drive CO 2 conversion on Cu x O and simultaneously oxidize water on WO 3 without an external power supply. In this stand-alone system, the primary CO 2 conversion product is CO, with a solar-to-chemical energy efficiency of ~2.5%; H 2 and formate are obtained with energy efficiencies of 0.7% and 0.25%, respectively, in 5 h (overall efficiency ~3.45%). Neither CO 2 conversion product nor H 2 is found using the single-absorber system. [ABSTRACT FROM AUTHOR]

Fluctuational electrodynamics and minority carrier diffusion equations are applied to evaluate the electric power output of a near-field tandem thermophotovoltaic (TPV) system with a bulk tungsten emitter (at 1500 K) and InGaSb/InAs tandem cells (at 300 K). We give evidence of the superiority of the tandem TPV system over the single-junction TPV system in the near-field regime because a tandem structure can harvest useful photons in a wider spectral range. It is also found that in comparison with the system with a bulk tungsten emitter, the practically achievable indium‑tin‑oxide (ITO) emitter and multilayer emitter could enhance the electricity output by a factor of 1.7 and 2.9 as a result of the supported surface plasmon resonances and hyperbolic modes, respectively. The conversion efficiency of the ITO emitter is 6% higher due to the suppression of the surface recombination loss, but the efficiency of the multilayer emitter is even 15% lower because of the heavy bulk recombination loss. These results highlight the possibilities to enhance the performance of the near-field tandem TPV systems via optimizing the radiative absorption distribution in the tandem cells, which is paramount important for the design and improvement of near-field tandem TPV systems. • The performance of a near-field tandem TPV system is theoretically investigated. • The near-field tandem TPV system is superior to the single-junction one. • The impacts of surface plasmonic resonance and hyperbolic modes are examined. • ITO and multilayer emitters can enhance electric power by 1.7 times and 2.9 times, respectively. • Physical mechanisms enabling higher or lower conversion efficiency are analyzed. [ABSTRACT FROM AUTHOR]

Large voltage losses are the main obstacle for achieving high efficiency in organic solar cells (OSCs). Here we construct ternary OSCs by introducing an asymmetric small molecule acceptor AITC into PBDB-TCl : BTP-eC9 system and demonstrate the effectiveness in simultaneously decreasing energy disorder and non-radiative voltage losses. It is found that the introduction of AITC can modify domain size and increase the degree of crystallinity, which enhances open-circuit voltage and power conversion efficiency (19.1%, certified as 18.9%). Inspiringly, an output efficiency of 20.6% of the constructed tandem OSCs based on PBDB-TCl : AITC : BTP-eC9 ternary active layer output a recorded efficiency of 20.6% (certified as 20.3%), which is the highest value in OSCs field to date. This work demonstrates that decreasing the voltage losses by ternary strategy and constructing of tandem architecture are effective approaches towards improving photovoltaic performance., (© The Author(s) 2023. Published by Oxford University Press on behalf of China Science Publishing & Media Ltd.)

We design a thermo-photovoltaic Tandem cell which produces high open circuit voltage ( V oc ) that causes to increase efficiency ( η ). The currently used materials (AlAsSb–InGaSb/InAsSb) have thermo-photovoltaic (TPV) property which can be a p – n junction of a solar cell, but they have low bandgap energy which is the reason for lower open circuit voltage. In this paper, in the bottom cell of the Tandem, there is 30 quantum wells which increase absorption coefficients and quantum efficiency (QE) that causes to increase current. By increasing the current of the bottom cell, the top cell thickness must be increased because the top cell and the bottom cell should have the same current. In the top cell, by increasing the thickness, absorption coefficients and quantum efficiency increase that causes to increase the current. Current increment is also the second factor that causes to increase overall efficiency. [ABSTRACT FROM AUTHOR]

Optical characteristics of the top and bottom cells in Cd 1− x Mg x Te/CuInSe 2 tandem solar cells with transparent ZnTe interconnection layer are investigated. Since the reflection coefficient is significantly attenuated in the case of Cd 1− x Mg x Te/ZnTe interface in comparison to the Cd 1− x Mg x Te/glass interface, the transmission through the monolithic top cell of the tandem can be calculated ignoring the oscillations. It has been shown that the short-circuit currents in the top and bottom solar cells match when the bandgap of Cd 1− x Mg x Te is in the range 1.67–1.70 eV. A good agreement between the measured and calculated periodic oscillations in the top cell transmittance has been demonstrated. It has been shown that the current matching can be achieved with a lower band gap Cd 1− x Mg x Te top-cell when borosilicate glass substrate is used, and also the short circuit current density is higher, compared to soda lime glass. [ABSTRACT FROM AUTHOR]

Silicon carbide/silicon rich carbide multilayers, aimed at the formation of silicon nanodots for photovoltaic applications, have been studied. The electrical properties have been investigated at the nano-scale by conductive Atomic Force Microscopy (c-AFM) and at macro-scale by temperature dependent conductivity measurements. The mixture is composed of highly conductive Si nanoclusters and moderately conductive SiC nanoclusters in a disordered matrix. The conduction mechanism takes place via band states induced by the disorder at the interface between nanodot clusters. Structural properties have been extracted by optical spectroscopy analyses. The results contribute to the understanding of the microscopical electronic mechanisms of the composite material, which is a candidate for third generation photovoltaics. [ABSTRACT FROM AUTHOR]

In this paper, the selective illumination approach is adopted to separately extract the shunt resistance of the individual subcells belonging to a tandem cell. The method relies on simple theoretical considerations and is based on the measurement of the current-voltage characteristic of the tandem cell by alternately keeping one of the subcells under dark conditions. Numerical simulations are employed to support the reliability of the technique, which is experimentally tested on micromorph devices deposited onto glass covered by a V-shaped transparent conducting oxide and subject to different thermal treatments. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We report on fabrication and testing of an all-organic-dye-based photovoltaic cell using a tandem architecture. Proceeding from the well-known concept of stacked molecular p/n-junctions, we developed a device with two stacked Schottky barrier subcells. Both subcells are based on p-type organic dyes: boron subphthalocyanine chloride (SubPc/Al barrier) for the front cell and vanadyl phthalocyanine (PcVO/Mg:Ag barrier) for the back one. These two dyes are complementary to each other in terms of optical activity, so the newly formed tandem cell absorbs a broad range of wavelengths from 300 to 1100 nm. Introduction of ultrathin intermediate layer of a third conductive dye, vanadyl naphthalocyanine (NcVO), at the Al/PcVO interface makes possible a serial connection of subcells, resulting in summation of open circuit voltages. [ABSTRACT FROM AUTHOR]

Wide-bandgap (WBG) nonfullerene acceptors (NFAs) with nonfused conjugated structures play a critical role in organic photovoltaic (OPV) cells. Here, NFAs named GS-OEH, GS-OC6, and GS-ISO, with optical bandgaps larger than 1.70 eV, are synthesized without using the fused ring structures. Compared with GS-OEH and GS-OC6, GS-ISO exhibits much stronger crystallinity, leading to a smaller energetic disorder and a larger exciton diffusion coefficient. GS-ISO also possesses a higher electroluminescence external quantum efficiency of 1.0 × 10 -2 . The OPV cell based on PBDB-TF:GS-ISO demonstrates a power conversion efficiency (PCE) of 11.62% under the standard one sun illumination. Besides, the PBDB-TF:GS-ISO-based cell with effective area of 1.0 cm 2  exhibits a PCE of 28.37% under 2700 K illumination of 500 lux. A tandem OPV cell using PBDB-TF:GS-ISO as the front subcell shows an outstanding efficiency of 19.10%. Importantly, the GS-ISO-based OPV cell exhibits promising stability under the continuous illumination of simulated sunlight. This study indicates that the molecular design strategy demonstrated in this work has great superiority in developing nonfused NFAs and also that GS-ISO is a promising WBG acceptor for versatile photovoltaic applications., (© 2021 Wiley-VCH GmbH.)

Motivated by the complete lack of theoretical knowledge in view of their applications in solar device processing and in optoelectronics, I have here investigated the structural and the electronic properties of interfaces constituted by the most relevant technological surface of silicon, i.e. the (001), and methylammonium (MA) lead iodide (001)-oriented surfaces. Results show a thermodynamic enhanced stability in the case of the lead iodide (PbI 2 -) terminated CH 3 NH 3 PbI 3 /Si interface, while the other investigated termination, the MAI-rich one, shows a better alignment between bandedges once interfaced with Si. Indeed, while for the latter a clear type-II heterojunction is observed, the former still shows a type-II behavior where anyway conduction band minima of Si and CH 3 NH 3 PbI 3 are (almost) degenerate. The DOS show the raise of p -like states in the gap close to the valence band due to the strain present at the Si-Si and at the equatorial Pb-I bonds in the PbI 2 -terminated/Si interface and indicate the unsuitability of this interface for optoelectronic applications. The present work reveals how the chemistry of the interface, i.e. the different bonding arrangement between silicon and CH 3 NH 3 PbI 3 , induces completely different carrier transport properties along the heterostructure with potentially detrimental effects in the final device. To date, this work is the first theoretical modellization of the interface between these two semiconductors and provides important information in the processes involved in 2-terminal tandem device assembling and in all the processes of perovskite growth on silicon substrate. Details of the wavefunction distribution of the Valence Band maximum of the Si/CH 3 NH 3 PbI 3 (MAI-terminated) interface. Image 1 • Realistic silicon/CH 3 NH 3 PbI 3 stress-free interfaces are here assembled and optimized by means of a first-principles parameter-free approach for the very first time. • Both terminations, i.e. PbI 2- and CH 3 NH 3 I-, are considered in the interface formation with Si (001) surface. • Strain at the interface is found to play a fundamental role in the final optoelectronic applicability of such nanohybrids. • Si/CH 3 NH 3 PbI 3 (CH 3 NH 3 I-terminated) interfaces have a clear type-II heterojunction behavior but are less thermodynamically favored. • Si/CH 3 NH 3 PbI 3 (PbI 2- terminated) interfaces show a worse bandoffset alignment for optoelectronic applications (regardless their more favorable formation). [ABSTRACT FROM AUTHOR]

Solution processable organic semiconductors are well‐established as high‐performance materials for inexpensive and scalable solar energy conversion in organic photovoltaic (OPV) devices, but their promise in the economic conversion of solar energy into chemical energy (solar fuels) has only recently been recognized. Herein, the main approaches employing organic semiconductor‐based devices toward solar H2 generation via water splitting are compared and performance demonstrations are reviewed. OPV‐biased water electrolysis is seen to advance significantly with the development of the tandem OPV device and the optimization of operating potential and redox catalysts. This approach now exceeds 6% solar‐to‐hydrogen conversion efficiency while over 10% is reasonably feasible. By contrast, while the direct water splitting by an organic semiconductor in a photo‐electrochemical cell has attractive advantages, increasing the performance remains a challenge. Photocathodes employing a bulk‐heterojunction have been optimized to give 7–8 mA cm−2 water reduction photocurrent under standard conditions, but photoanodes remain <1 mA cm−2, and robustness remains a critical issue. However, recent investigations into the direct organic semiconductor/electrolyte interface have brought important insights into free charge generation, the nature of the semiconductor/catalyst interface, and the stability of organic photoelectrodes. Outlooks toward advancing both approaches are discussed. Splitting water with sunlight and organic semiconductor devices is emerging as a promising approach for the inexpensive and scalable solar fuel production. Herein, organic semiconductor based devices for solar water splitting are systematically reviewed. The challenges facing the advance of both photovoltaic‐based electrolysis and photo‐electrochemical cells are highlighted while new directions to consolidate these technologies are proposed. [ABSTRACT FROM AUTHOR]

Photovoltaic retinal prostheses show great potential to restore sight in patients suffering from degenerative eye diseases by electrical stimulation of the surviving neurons in the retinal network. Herein, organic photodiodes (OPDs) sensitive to near-infrared (NIR) light are evaluated as photovoltaic pixels for future application in retinal prostheses. Single-junction and tandem OPDs are compared. In the latter, two nominally identical single-junction cells are processed on top of each other, effectively doubling the open-circuit voltage (V OC ). Both single-junction and tandem OPD micropixels can deliver the required charge to stimulate neurons under pulsed NIR light at physiologically safe intensities when connected to stimulating microelectrodes in a physiological saline solution. However, only tandem OPD pixels can cover the entire charge per pulse neural stimulation window due to their higher V OC (≈1.4 V). This demonstrates the viability of high-resolution retinal prostheses based on flexible OPD arrays., (© 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In this work, a highly efficient parallel connected tandem solar cell utilizing a nonfullerene acceptor is demonstrated. Guided by optical simulation, each of the active layer thicknesses of subcells are tuned to maximize its light trapping without spending intense effort to match photocurrent. Interestingly, a strong optical microcavity with dual oscillation centers is formed in a back subcell, which further enhances light absorption. The parallel tandem device shows an improved photon-to-electron response over the range between 450 and 800 nm, and a high short-circuit current density (J SC ) of 17.92 mA cm -2 . In addition, the subcells show high fill factors due to reduced recombination loss under diluted light intensity. These merits enable an overall power conversion efficiency (PCE) of >10% for this tandem cell, which represents a ≈15% enhancement compared to the optimal single-junction device. Further application of the designed parallel tandem configuration to more efficient single-junction cells enable a PCE of >11%, which is the highest efficiency among all parallel connected organic solar cells (OSCs). This work stresses the importance of employing a parallel tandem configuration for achieving efficient light harvesting in nonfullerene-based OSCs. It provides a useful strategy for exploring the ultimate performance of organic solar cells., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)