High-efficiency Solar Cells Research Articles

Theoretical study of the strong piezo-phototronic effect in 2D monochalcogenides for multi-junction solar cells

The piezophototronic effect is a new scientific area that investigates the synergistic interactions of piezoelectric, semiconductor, and photoexcitation features. This effect is seen in crystals lacking inversion symmetry, where applied strain alters electronic transport and provides a way to modify material properties. Monolayer 2D semiconductors, such as transition metal dichalcogenides (TMDCs) and group IV monochalcogenides, have higher piezoelectric coefficients than conventional piezoelectric materials. This study proposes the development of a stable, high-performance multijunction solar cell (MJSC) leveraging the piezo-phototronic effect. The emphasis is on single-type 5-layer 2D monochalcogenides (SnS, SnSe, GeS, and GeSe) with the assistance of strain engineering. Surprisingly, the ultrathin parallel-connected solar cell achieves an electric power conversion efficiency of over 31% when tested under blackbody radiation, surpassing the recognized Shockley–Queisser (S-Q) limit. The piezophototronic effect improves solar cell performance while also addressing voltage mismatch issues. This work introduces a novel approach to developing and manufacturing high-efficiency and robust monolayer multijunction photovoltaic solar cells (MJPSC) based on 2D monochalcogenides.

Cu gradient design to attain high efficient solution-processed CuIn(S,Se)2 solar cells

Solution-processed chalcopyrite solar cells are widely regarded as a promising alternative method in reducing the cost compared with vacuum-based techniques. It is noted that the absorber layer usually needs to be prepared under a high insert pressure (∼1.6 atm) to suppress element loss or under a mild pressure but additional surface etching is needed for fabricating high efficient solar cell. Herein, a copper gradient structured precursor is proposed to prepare CuIn(S,Se)2 (CISSe) film under a mild pressure (1.1 atm). The designed gradient Cu not only promotes crystal grain growth and tailors the defects, but also avoids the surface etching of the formed CISSe film for the fabrication of high efficient solar cells. Further, Cu gradient design decreases the conduction band offset of heterojunction, boosting the carriers transport across the p-n heterojunction. Accordingly, a 13.35% efficient CISSe solar cell, comparable to the high efficient CISSe solar cell prepared by this method under high pressure or with film surface etching, is fabricated. This work provides a facile pathway to fabricate high efficient solution-processed chalcopyrite solar cell, avoiding high selenization pressure and film etching, and shows huge potential for solution-processed copper-based solar cells.

Endgroup engineering of the third component for high-efficiency ternary organic solar cells

In this study, we carefully designed and synthesized three A-D-A type molecules, namely YF-C8-CN, YF-C8-S, and YF-C8-O. These molecules feature a 2,2′-bithiophene core, which bears two 2,4,6-tripropylbenzene steric hindrance groups, as the central electron-donating unit, and utilize rhodanine (Rh), thiazolidinedione, and dicyanoyl-modified benzotriazole (BTA) respectively as the electron acceptor unit (A-unit). We investigated their impact as the third component on the performance of ternary organic solar cells (OSCs). Our studies indicate that YF-C8-S, with rhodanine terminal groups, exhibits complementary absorption characteristics and cascaded energy levels when combined with the host binary system (D18:eC9-4F). Compared to YF-C8-CN and YF-C8-O, ternary OSCs based on YF-C8-S demonstrate significantly higher exciton diffusion and charge transport efficiency, favorably impacting the short-circuit current density (JSC) and fill factor (FF) of the OSCs. Furthermore, devices based on YF-C8-S exhibit reduced non-radiative energy loss, contributing to an enhanced open-circuit voltage (VOC). Consequently, ternary OSCs based on YF-C8-S achieve a remarkable efficiency of 19.12%, positioning it among the highest reported values. This comprehensive research on the third component of the YF-C8 series underscores their significant potential for fabricating high-performance ternary OSCs.

High efficiency Sb and Ag double doped Cu2ZnSn(S, Se)4 thin film solar cells realized by post-heat treatment process of heterojunction

Cu2ZnSn (S, Se)4 (CZTSSe) semiconductors have become a recent focus of research owing to their cost-effectiveness, environmental friendliness, and high efficiency. However, insufficient band alignment between the CZTSSe absorption layer and the CdS buffer layer significantly hampers the high conversion efficiency of CZTSSe devices. In this study, problems related to energy-band matching were solved by the post-heat treatment (PHT) of the absorber and buffer layers. Based on obtaining a high-quality absorption layer through double-doped (Cu, Ag)2Zn(Sn, Sb)(S, Se)4 (CAZTSSSe), the impact of the PHT process of CAZTSSSe/CdS on the device performance and heterojunction quality was investigated. The PHT process promoted the reciprocating motion of elements in the heterojunction region, directly inducing the movement of Cd towards the absorption layer and Cu towards the buffer layer. Furthermore, the PHT method enhances the recrystallization of CdS, resulting in the formation of a CdS layer with excellent crystalline quality. After PHT processing, a more favorable conduction band arrangement was obtained, which helps to reduce non-radiative recombination. Ultimately, when the PHT temperature reaches 200 °C, we get an optimal device with an efficiency of up to 9.44 %, as open circuit voltage (VOC) escalates to 431 mV, and lower fill factor (FF) attains 55.63 %. It is believed that this PHT process can be better applied in thin film cells to obtain high-efficiency solar cells.

Enhanced charge separation at the interface of Cu2O/CuSCN composite thin films synthesized by electrodeposition technique

This study focuses on the synthesis and characterization of hole transport layers (HTLs) for solar cells, par- ticularly copper(I) thiocyanate (CuSCN) and cuprous oxide (Cu2O), synthesized via electrodeposition tech- niques. CuSCN and Cu2O offer promising properties for efficient charge transport in photovoltaic devices. The synthesis processes involve precise control of deposition parameters to achieve desired film morpholo- gies and properties. Characterization techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), and ultraviolet-visible (UV-Vis) spectroscopy provide insights into film morphology and optical properties. Optimization of synthesis parameters for Cu2O films is explored to enhance their electrical properties. Photoelectric response measurements indicate improved charge separation at the interface of Cu2O/CuSCN composite films. These findings can contribute to the advancement of solar cell technology. Furthermore, the study extends its exploration to the fabrication of Cu2O by electrodeposition at different pH levels. SEM and X-ray diffraction (XRD) analyses reveal the impact of deposition parameters on film mor- phology and crystal structure, providing valuable insights for tailored synthesis approaches. Overall, this comprehensive study not only advances the understanding of HTL materials synthesis and optimization but also provides valuable guidance for the development of high-efficiency and stable solar cell devices.

Optimizing CuInSe2 solar cells with kesterite-based upper absorber and back surface field layers for enhanced efficiency: a numerical study

Abstract This study explores the performance enhancement of an innovative multi-layer solar cell structure using the SCAPS-1D (Solar Cell Capacitance Simulator in One Dimension) software. We aim to improve the efficiency of a solar cell structure comprising ZnO/ZnSe/CZTSe/CuInSe2/CZTSSe/Mo by incorporating CZTSe as the upper absorber layer, CuInSe2 as the main absorber layer, and CZTSSe as a back surface field (BSF) layer. Initially, we compare the performance of three different configurations by analyzing their J-V characteristics. For the best performing structure, we further examine the external quantum efficiency (EQE) spectrum. We then evaluate various window (ZnO, ZnMgO, SnO2, Zn2SnO4) and buffer (ZnSe, ZrS2, SnS2, In2S3) materials, identifying ZnO and ZrS2 as the most effective for achieving high current density and efficiency. Through detailed simulations, we determine the optimal thicknesses for CZTSSe (0.2 µm), CZTSe (0.4 µm), and CuInSe2 (3.2 µm). Additionally, by optimizing the acceptor density to 1020 cm−3, we significantly enhance the performance of both CZTSe and CZTSSe layers. Temperature management is shown to be crucial, with the highest efficiency observed at 300 K. As a result of these optimizations, the solar cell structure achieves a remarkable efficiency of 35.38%. Furthermore, we compare our results with existing literature to highlight the advancements made in this study. These findings underscore the importance of material selection and structural optimization in developing high-efficiency solar cells and provide a framework for future advancements in photovoltaic technology.

Inner Side Chain Modification of Small Molecule Acceptors Enables Lower Energy Loss and High Efficiency of Organic Solar Cells Processed with Non-halogenated Solvents.

Organic solar cells (OSCs) processed with non-halogenated solvents usually suffer from excessive self-aggregation of small molecule acceptors (SMAs), severe phase separation and higher energy loss (Eloss), leading to reduced open-circuit voltage (Voc) and power conversion efficiency (PCE). Here, we designed and synthesized two SMAs L8-PhF and L8-PhMe by introducing different substituents (fluorine for L8-PhF and methyl for L8-PhMe) on the phenyl end group of inner side chains of L8-Ph, and investigated the effect of the substituents on the intermolecular interaction of SMAs, Eloss and performance of OSCs processed with non-halogenated solvents. It is found that compared with L8-PhF, which possesses strong intermolecular interactions but downgraded molecular packing order, L8-PhMe exhibits more effective non-covalent interactions, which improves the tightness and order of molecular packing. When blending the SMAs with PM6, the OSCs based on L8-PhMe shows reduced non-radiative energy loss, and enhanced Voc than the devices based on the other two SMAs. Consequently, the L8-PhMe based device processed with o-xylene and using 2PACz as the hole transport layer shows an outstanding PCE of 19.27%. This study highlights that the Eloss of OSCs processed with non-halogenated solvents could be decreased through regulating the intermolecular interactions of SMAs by inner side chain modification.

Comprehensive evaluation of recombination confined performance of CuGaO2 for solar cell application

In the quest to find an outstanding solar energy capturing system that meets requirements like affordability, widespread availability, eco-friendliness, remarkable efficiency, and enduring stability, thorough investigations have been carried out to explore the possibilities presented by ‘Delafossite’ copper gallium oxide (CuGaO2). β-CuGaO2 has an ideal bandgap of 1.5 eV, along with a high absorption coefficient and excellent carrier mobility, making it well-suited for high-efficiency solar cell applications. Theoretical modelling, utilizing the optical and electrical attributes of the CuGaO2 (CGO) material, is employed to analyze its photovoltaic performance when used as an absorber. The detailed balance analysis showed 56.9% of the incident power is wasted in spectrum loss (as thermalisation and non-absorption loss), 10.1% is wasted in intrinsic losses (such as radiative recombination, radiation dilution, entropy generation etc,), extrinsic recombination (originating from electrical losses, parasitic resistance, finite mobility, surface recombination velocity (SRV), non-ohmic contacts etc), eats up another 9.5% and the resultant 23.6% is available as net useful efficiency. Through the careful selection of a suitable buffer counterpart and optimization of material parameters, absorber thickness, defect density, contacts, and SRV, the CGO device dem onstrates an efficiency of 23.6%.

Computational Optimization for CdS/CIGS/GaAs Layered Solar Cell Architecture

Multi-junction solar cells are vital in developing reliable, green, sustainable solar cells. Consequently, the computational optimization of solar cell architecture has the potential to profoundly expedite the process of discovering high-efficiency solar cells. Copper indium gallium selenide (CIGS)-based solar cells exhibit substantial performance compared to those utilizing cadmium sulfide (CdS). Likewise, CIGS-based devices are more efficient according to their device performance, environmentally benign nature, and thus, reduced cost. Therefore, the paper introduces an optimization process of three-layered n-CdS/p-CIGS/p-GaAs (NPP)) solar cell architecture based on thickness and carrier charge density. An in-depth investigation of the numerical analysis for homojunction PPN-junction with the ’GaAs’ layer structure along with n-ZnO front contact was simulated using the Solar Cells Capacitance Simulator (SCAPS-1D) software. Subsequently, various computational optimization techniques for evaluating the effect of the thickness and the carrier density on the performance of the PPN layer on solar cell architecture were examined. The electronic characteristics by adding the GaAs layer on the top of the conventional (PN) junction further led to optimized values of the power conversion efficiency (PCE), open-circuit voltage (VOC), fill factor (FF), and short-circuit current density (JSC) of the solar cell. Lastly, the paper concludes by highlighting the most promising results of our study, showcasing the impact of adding the GaAs layer. Hence, using the optimized values from the analysis, thickness of 5 (μm) and carrier density of 1×1020 (1/cm) resulted in the maximum PCE, VOC, FF, and JSC of 45.7%, 1.16 V, 89.52%, and 43.88 (mA/m2), respectively, for the proposed solar cell architecture. The outcomes of the study aim to pave the path for highly efficient, optimized, and robust multi-junction solar cells.

Multifunctional Guanidine Ionic Liquid with Lactate Anion-Assisted Crystallization and Defect Passivation for High-Efficient and Stable Perovskite Solar Cells

Multifunctional Guanidine Ionic Liquid with Lactate Anion-Assisted Crystallization and Defect Passivation for High-Efficient and Stable Perovskite Solar Cells

Unravelling Singlet Fission in Polymer Materials: Mechanisms, Challenges, and Prospects for High-Efficiency Solar Cells

Unravelling Singlet Fission in Polymer Materials: Mechanisms, Challenges, and Prospects for High-Efficiency Solar Cells

Oligomerized Acceptors with High Efficiency and Superior Stability in Organic Solar Cells.

Oligomerized small molecular acceptors (OSMAs) have rapidly become a research hotspot in the field of organic solar cells due to their advantages of effective combination with definite structure of small molecules and high viscosity and glass transition temperature of polymers. From this perspective, we classify and summarize the representative OSMAs from the three binding sites of end, core, and wing, and we summarize the exploration of new synthesis methods to improve the plights, such as low synthesis yield and difficult purification. Finally, the existing challenges and future research directions are concluded and prospected.

Multifunctional Acetaminophen Interlayer for High Efficiency and Durability Lead-Lean Perovskite Solar Cells.

Due to the easy oxidation of Sn2+, which leads to form tin vacancy defects and poor perovskite film quality, caused by the rapid crystallization rate in tin-based perovskite solar cells (PSCs), their efficiency lags far behind that of lead-based PSCs. To improve the photovoltaic (PV) performance and stability of FA0.9PEA0.1SnI3-based PSCs (T-PSCs), a small amount of Pb(SCN)2 is introduced into a perovskite precursor as an antioxidant, and acetaminophen (ACE) with various functional groups is used to modify a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/perovskite interface. The results show that the Pb(SCN)2 additive and ACE interfacial modification can not only optimize energy level alignment in T-PSCs but also inhibit Sn2+ oxidation to reduce the trap-state density, resulting in promoted carrier transport. The synergetic effect of the Pb(SCN)2 antioxidant and ACE interfacial modification significantly reduces nonradiative recombination and improves the PV performance and stability of T-PSCs. Consequently, the unsealed T-PSCs with the Pb(SCN)2 additive and ACE modification achieve a champion efficiency of 12.04% and maintain 99% of their initial PCE after being stored in N2 for more than 2100 h, while reference T-PSCs demonstrate a champion PCE of 6.20% and retain only 72% of its initial PCE. Moreover, the modified T-PSCs without encapsulation demonstrate much better stability in humid air.

Heterogeneous Nucleation Regulation Amends Unfavorable Crystallization Orientation and Defect Features of Antimony Selenosulfide Film for High-Efficient Planar Solar Cells.

Antimony selenosulfide (Sb2(S,Se)3) has obtained widespread concern for photovoltaic applications as a light absorber due to superior photoelectric features. Accordingly, various deposition technologies have been developed in recent years, especially hydrothermal deposition method, which has achieved a great success. However, device performances are limited with severe carrier recombination, relating to the quality of absorber and interfaces. Herein, bulk and interface defects are simultaneously suppressed by regulating heterogeneous nucleation kinetics with barium dibromide (BaBr2) introduction. In details, the Br adsorbs and dopes on the polar planes of cadmium sulfide (CdS) buffer layer, promoting the exposure of nonpolar planes of CdS, which facilitates the favorable growth of [hk1]-Sb2(S,Se)3 films possessing superior crystallinity and small interface defects. Additionally, the Se/S ratio is increased due to the replacement of S/Se by Br, causing a downshift of the Fermi levels with a benign band alignment and a shallow-level defect. Moreover, Ba2+ is located at grain boundaries by coordination with S and Se ions, passivating grain boundary defects. Consequently, the efficiency is increased from 7.70% to 10.12%. This work opens an avenue towards regulating the heterogeneous nucleation kinetics of Sb2(S,Se)3 film deposited via hydrothermal deposition approach to optimize its crystalline orientation and defect features.

Effect of bromine on the formation of δ-CsPbI3 in Cs0.22FA0.78Pb(I1-xBrx)3 perovskite solar cells

Applying CsxFA1-xPbI3 perovskite is a useful strategy for synthesizing high-efficiency organic-inorganic lead halide perovskite solar cells because it improves the stability of the perovskite structure. High concentration of cesium (Cs) in CsFAPbI3 synthesized under ambient conditions typically lead to phase separation due to δ-CsPbI3 formation and moisture, thereby reducing light absorption and increasing non-radiative recombination. To counter this, we fabricated the mixed halide Cs0.22FA0.78Pb(I1-xBrx)3 perovskite films. Introducing bromine (Br) content effectively reduced the δ-CsPbI3 formation and grain boundaries, thus suppressing the non-radiative recombination between perovskite and charge transport layers. Employing this approach, our perovskite solar cells with a 10 % Br concentration achieved a power conversion efficiency of 15.81 %. This demonstrates the potential of Br incorporation in enhancing the stability and efficiency of perovskite solar cells.

Dimeric Small Molecule Acceptors via Terminal-End Connections: Effect of Flexible Linker Length on Photovoltaic Performance.

The dimerization of small molecule acceptors (SMAs) holds significant potential by combining the advantages of both SMAs and polymer acceptors in realizing high power conversion efficiency (PCE) and operational stability in organic solar cells (OSCs). However, advancements in the selection and innovation of dimeric linkers are still challenging in enhancing their performance. In this study, three new dimeric acceptors, namely DY-Ar-4, DY-Ar-5, and DY-Ar-6 are synthesized, by linking two Y-series SMA subunits via an "end-to-end" strategy using flexible spacers (octyl, decyl, and dodecyl, respectively). The influence of spacer lengths on device performance is systematically investigated. The results indicate that DY-Ar-5 exhibits more compact and ordered packing, leading to an optimal morphology. OSCs based on PM6: DY-Ar-5 achieves a maximum PCE of 15.76%, attributes to enhance and balance carrier mobility, and reduce carrier recombination. This dimerization strategy using suitable non-conjugated linking units provides a rational principle for designing high-performance non-fullerene acceptors.

Mapping Spatial Strain Distribution and Its Effects on Optoelectronic Properties in Wrinkled Perovskite Films.

Organic-inorganic halide perovskite films, fabricated by using the antisolvent method, have garnered intense attention for their application in high-efficiency and stable solar cells. These films characteristically develop periodic wrinkled microstructures. Previous research has indicated that macroscopic residual strain significantly influences the optoelectronic behaviors of these films. However, the detailed interplay between the wrinkled morphology, strain distribution, and local photophysical properties at the micro- and nanoscale has not been fully elucidated. Here, we explore the microscopic morphology-strain-property relationship within wrinkled perovskite films employing correlative micro-optical and nanoelectrical microscopy techniques. Microphotoluminescence (PL) mapping supplemented by in situ strain PL measurements identifies a heterogeneous spatial strain distribution across the microstructural hills and valleys. Additionally, light-intensity-dependent photoconductive atomic force microscopy reveals that valleys experiencing less compressive strain exhibit a lower conductivity and a higher propensity for ion migration. The findings underscore the potential of targeted strain engineering to optimize the performance and longevity of perovskite solar cells.

SnSe2 Quantum Dots and Chlorhexidine Acetate Suppress Synergistically Non-radiative Recombination Loss for High Efficiency and Stability Perovskite Solar Cells.

Non-radiative recombination losses limit the property of perovskite solar cells (PSCs). Here, a synergistic strategy of SnSe2QDs doping into SnO2 and chlorhexidine acetate (CA) coating on the surface of perovskite is proposed. The introduction of 2D SnSe2QDs reduces the oxygen vacancy defects and increases the carrier mobility of SnO2. The optimized SnO2 as a buried interface obviously improves the crystallization quality of perovskite. The CA containing abundant active sites of ─NH2/─NH─, ─C═N, CO, ─Cl groups passivate the defects on the surface and grain boundary of perovskite. The alkyl chain of CA also improves the hydrophobicity of perovskite. Moreover, the synergism of SnSe2QDs and CA releases the residual stress and regulates the energy level arrangement at the top and bottom interface of perovskite. Benefiting from these advantages, the bulk and interface non-radiative recombination loss is greatly suppressed and thereby increases the carrier transport and extraction in devices. As a result, the best power conversion efficiency (PCE) of 23.41% for rigid PSCs and the best PCE of 21.84% for flexible PSCs are reached. The rigid PSC maintains 89% of initial efficiency after storing nitrogen for 3100 h. The flexible PSCs retain 87% of the initial PCE after 5000 bending cycles at a bending radius of 5 mm.

A Review: Application of Doped Hydrogenated Nanocrystalline Silicon Oxide in High Efficiency Solar Cell Devices.

Due to the unique microstructure of hydrogenated nanocrystalline silicon oxide (nc-SiOx:H), the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to different solar cell applications. In this work, the authors review the material properties of nc-SiOx:H and the versatility of its applications in different types of solar cells. The review starts by introducing the growth principle of doped nc-SiOx:H layers, the effect of oxygen content on the material properties, and the relationship between optoelectronic properties and its microstructure. A theoretical analysis of charge carrier transport mechanisms in silicon heterojunction (SHJ) solar cells with wide band gap layers is then presented. Afterwards, the authors focus on the recent developments in the implementation of nc-SiOx:H and hydrogenated amorphous silicon oxide (a-SiOx:H) films for SHJ, passivating contacts, and perovskite/silicon tandem devices.

Anti-solvent materials enhanced structural and optical properties on ambiently fabricated perovskite thin films

Perovskite solar cells (PSCs) hold potential for low-cost, high-efficiency solar energy, but their sensitivity to moisture limits practical application. Current fabrication requires controlled environments, limiting mass production. Researchers aim to develop stable PSCs with longer lifetimes under ambient conditions. In this research work, we investigated the stability of perovskite films and solar cells fabricated and annealed in natural air using four different anti-solvents: toluene, ethyl acetate, diethyl ether, and chlorobenzene. Films (about 300 nm thick) were deposited via single-step spin-coating and subjected to ambient air-atmosphere for up to 30 days. We monitored changes in crystallinity, electrical properties, and optics over time. Results showed a gradual degradation in the films’ crystallinity, morphology, and electro-optical properties. Notably, films made with ethyl acetate exhibited superior stability compared to other solvents. These findings contribute to advancing stable and high-performance PSCs manufactured under normal ambient conditions. In addition, we also discuss the possible machine learning (ML) approach to our future work direction to optimize the materials structures, and synthesis process parameters for future high-efficient perovskite solar cells fabrication.