Photovoltaic Materials Research Articles

Standing 1D Chains Enable Efficient Wide-Bandgap Selenium Solar Cells.

The recent surge in tandem solar cells and indoor photovoltaics has renewed interest in selenium (Se), the world's first photovoltaic material, due to its intrinsic wide bandgap of ≈1.9eV, high stability, and non-toxicity in small quantities when applied in photovoltaics. However, with a 1D chained crystal structure, Se tends to grow crystalline films with a lying orientation-chains parallel to substrates arising from the low surface energy; this results in poor carrier transport across chains held together by weak van der Waals forces. Here a substrate-heating strategy that facilitates the interfacial bonding between Se and substrate is introduced, enabling the growth of Se films with a standing orientation-chains perpendicular to substrates. This achieves efficient carrier transport along covalently bonded chains. The resulting Se films thereby exhibit a fourfold increase in carrier mobility compared to lying-oriented Se films. Consequently, Se solar cells are achieved with the highest power conversion efficiency of 8.1% under AM1.5G 1-sun illumination. The unencapsulated devices exhibit negligible efficiency loss after 1000 h of storage under ambient conditions.

Theoretical Insights into Ultrafast Separation of Photogenerated Charges in a Push-Pull Polarized Molecular Triad.

Herein, we propose a purely-organic donor-acceptor (D-A) molecular triad, with a light-absorbing polarized molecular wire (PMW) used as a central linkage, as a proof of concept for the possible future applications of the D-PMW-A arrangement in molecular photovoltaics. This work builds upon our earlier study on the PMW unit itself, which proved to be highly promising for the ultrafast photogeneration of free charge carriers. Quantum-chemical calculations performed for the D-PMW-A triad at a semi-empirical level of theory reveal a large electric dipole moment of the system, and show strong charge-transfer (CT) character of its lowest-energy excited electronic states, including the S1, which favours efficient dissociation of an exciton initially formed upon the absorption of light. The confirmation for this effect was found with nonadiabatic molecular dynamics simulations, revealing an ultrafast relaxation from higher, bright excited states to S1, completed on a subpicosecond timescale. The architecture of the proposed molecular triad enables its electronic coupling to the surrounding environment through chemical bonds, or noncovalent stacking interactions, which might open way for synthesis of a new class of D-PMW-A efficient molecular organic photovoltaic materials.

Furan-substituted benzodithiophene-based polymer semiconductor for charge transport materials in organic transistors and nanocrystal photovoltaics

Furan-substituted benzodithiophene-based polymer semiconductor for charge transport materials in organic transistors and nanocrystal photovoltaics

Interface-enhanced germanium selenide solar cells comprising an ultrathin and uniform antimony selenide buffer layer via hydrothermal approach

Germanium selenide (GeSe) is a promising thin film photovoltaic absorber material owing to its excellent optoelectronic properties, high stability, and low toxicity. Interface engineering by introducing an ultrathin antimony selenide (Sb2Se3) buffer layer between the CdS electron transport layer and GeSe absorber layer is an effective technique for enhancing solar cell performance. However, the key to this technique is the fabrication of a uniform and smooth Sb2Se3 buffer layer with minimal thickness. In this study, instead of the conventional closed-space sublimation method, a hydrothermal method was employed to slowly grow an Sb2Se3 buffer layer with a thickness of approximately 8 nm. The Se/Na2SO3 molar ratio in the selenium source during the hydrothermal synthesis was adjusted; a molar ratio of 1:2 led to an uneven Sb2Se3 buffer layer thickness, whereas a molar ratio of 1:10 resulted in the formation of Sb2O3 particles on the buffer layer surface. When the Se/Na2SO3 molar ratio was 1:6, a smooth, uniform, dense, and impurity-free Sb2Se3 buffer layer was obtained, achieving the highest efficiency of 3.33 % in a GeSe solar cell. Moreover, GeSe solar cells with hydrothermally grown Sb2Se3 buffer layers demonstrated superior device interface properties and efficiency comparable with those using Sb2Se3 buffer layers deposited via closed-space sublimation. This technique offers an effective method for steadily improving the performance of GeSe solar cells.

Fully Non-Fused Ring Electron Acceptors Enable Effective Additive-Free Organic Solar Cells with Enhanced Exciton Diffusion Length.

Low-cost photovoltaic materials and additive-free, non-halogenated solvent processing of photoactive layers are crucial for the large-scale commercial application of organic solar cells (OSCs). However, high-efficiency OSCs that possess all these advantages remain scarce due to the lack of insight into the structure-property relationship. In this work, three fully non-fused ring electron acceptors (NFREAs), DTB21, DTB22, and DTB23, are reported by utilizing a simplified 1,4-di(thiophen-2-yl)benzene (DTB) core with varied alkoxy chain lengths on the thiophene bridge. The material-only costs of these acceptors are only 11-13$ per gram. Importantly, DTB22 has an exciton diffusion length (LD) of up to 25.5nm. The DTB21 and DTB23 exhibit decreased LDs of 20.1 and 23.1nm, respectively. After blending with the polymer donor PBQx-TF, the PBQx-TF:DTB22 film exhibits the fastest hole transfer and the longest carrier recombination lifetime among these OSCs. Consequently, the optimal PBQx-TF:DTB22-based OSC achieves an excellent PCE of 17.00%, which is among the highest values for fully NFREAs. In contrast, the PBQx-TF:DTB21- and PBQx-TF:DTB23-based OSCs show relatively lower PCEs of 15.13% and 15.63%, respectively. Notably, all these OSCs are fabricated using toluene as the solvent, without any additives. Additionally, the DTB22-based OSC also demonstrates good stability, retaining 95% of its initial efficiency after 500 h without encapsulation in a glovebox.

Interplay Between the N→C Dative Bond, Intramolecular Chalcogen Bond and π Conjugation in the Complexes Formed by Cyclo[18]carbon and C14 Polyyne with 1,2,5-Chalcogenadiazoles.

The N→C dative bond (DB), intramolecular chalcogen bond and π conjugation play important roles in determining the structures and properties of some molecular carbon materials and organic/polymeric photovoltaic materials. In this work, the interplay between the N→C DB, intramolecular chalcogen bond and π conjugation in the complexes formed by cyclo[18]carbon and C14 polyyne with 1,2,5-chalcogenadiazoles has been investigated in detail by using reliable quantum chemical calculations. This study has made four main findings. First, only the Te-containing complexes bound by N→C DBs are much more stable than their corresponding van der Waals (vdW) complexes. Second, in addition to through-bond π conjugations, through-space π conjugations also exist in some Se/Te-containing complexes bound by N→C DBs. Third, the cooperativity between intramolecular chalcogen bond, π conjugation between two monomers and N→C DB is not very strong and can be ignored. Fourth, compared to π conjugations, intramolecular Ch⋅⋅⋅C (Ch=O, S, Se, Te) chalcogen bonds play a secondary role in stabilizing the complexes bound by N→C DBs. These findings clearly indicate that the role of "conformational lock", popular in the field of organic optoelectronic materials, may have been greatly overestimated.

A Study on Assessing Supply Chain Vulnerabilities of Solar Photovoltaic Materials and Components

A Study on Assessing Supply Chain Vulnerabilities of Solar Photovoltaic Materials and Components

Design and simulation of highly efficient CZTS/CZTSSe based thin-film solar cell

Thin-film solar cells are a substitute for more common crystalline silicon solar cells, which consist of thin semiconductor layers. Thin-film materials comprise direct bandgap and can absorb sunlight more efficiently than silicon. In this article, a double-absorber-based thin-film solar cell comprising CZTS/CZTSSe is designed and optimized through numerical simulation. The proposed solar cell structure consists of a transparent window layer made of aluminum-doped zinc oxide, followed by an intrinsic zinc oxide layer, an n-type cadmium sulfide layer, and a p-type combined absorber layer of copper zinc tin sulfide (Cu2ZnSnS4) (CZTS) and copper zinc tin sulfur-selenium alloy (Cu2ZnSn(S,Se4)) (CZTSSe). The structure is further optimized by introducing two interfacial layers between CZTSSe/CZTS and CZTS/CdS. The highest conversion efficiency is achieved by adjusting the thicknesses of the layers, the doping densities in different layers, and the defect densities in the two absorber layers. The optimized model, with a total thickness of 2.01 μm, demonstrates an open-circuit voltage (Voc) of 0.7669 V, a short-circuit current (Jsc) of 48.57740 mA/cm2, a fill factor (FF) of 70.61%, and efficiency (η) of 26.31%. These results suggest that CZTS is a promising candidate for replacing other thin-film photovoltaic materials, such as CdTe. The proposed double-absorber thin-film solar cell optimizes doping concentration, thickness, and defect density to enhance performance metrics and efficiency while utilizing non-toxic materials to promote cost-effective, environmentally friendly energy solutions.

Application and Research Progress of Perovskite in the Field of Optoelectronic Materials

Perovskite refers to a class of materials with the formula of ABO3. These oxides were first discovered in calcium titanate compounds. Perovskite materials have attracted widespread attention in the field of contemporary photovoltaic research due to their excellent photovoltaic properties, heralding their potential as protagonists of a new generation of photovoltaic materials. Nevertheless, the stability of perovskite materials needs to be enhanced. In addition, reducing the toxicity of the materials is a key challenge in advancing their commercialization. Currently, the rapid development of perovskite in the field of optoelectronics and its unique combination of properties have laid a solid foundation for its position as a mainstream optoelectronic material of the future. Therefore, this work focuses on the properties and applications of perovskite optoelectronics. With deeper scientific research and technological innovation, perovskites have the potential to overcome existing limitations and move towards large-scale commercial production. In the future, the further application of perovskite optoelectronic materials would have far-reaching implications for the global energy transition and environmental protection.

Probing into the low efficiency of CdS/SnS-based solar cells and remediation through surface treatments

Tin sulfide (SnS) is a highly promising photovoltaic absorption material in thin-film solar cells with abundant reserves, environmental friendliness, low cost and long-term stability. An efficiency of up to 4.8 % has been achieved for SnS absorber/CdS heterojunction solar cells where the CdS buffer layer is usually obtained by chemical bath deposition. However, current CdS/SnS devices often suffer from severe interface recombination loss, which deteriorates device performance. This report focuses on the CdS film surface to identify performance-degrading factors for CdS/SnS-based solar cells. XRD and XPS reveal numerous oxides on freshly fabricated CdS films increasing surface roughness and reducing conductivity. Herein, a method based on ammonium sulfide (AS) chemical treatment is proposed, which can effectively reduce the oxide content on the surface of CdS and optimize the band alignment, leading to the facilitation of charge carrier transport and the suppression of interface recombination. Consequently, the PCE of the FTO/CdS/SnS/Ag device is enhanced about three times (from 0.18 % to 0.47 %) with excellent moisture stability.

Effect of Chlorine Inclusion in Wide Band Gap FAPbBr3 Perovskites

AbstractWide bandgap perovskites have recently gained attention owing to their physical properties, versatility, and potential in various optoelectronic devices including LEDs, detectors, and building‐integrated photovoltaics (BIPV). However, BIPV materials must meet conflicting requirements, necessitating high performance, high transparency in the visible spectrum and color neutrality. This study investigates the controlled addition of chlorine in FAPb(Br1‐xClx)3 perovskites to achieve band gaps exceeding 2.4 eV. Increasing chlorine content from xCl = 0.00 to xCl = 0.25 widens the band gap from 2.37 to 2.52 eV, effectively improving the visible light transparency. Advanced characterization techniques including X‐ray diffraction, synchrotron radiation photoelectron spectroscopy, photoluminescence imaging, and fast transient absorption spectroscopy, complemented by density functional theory, reveal insights into absorption properties, electronic structure, and ultrafast recombination dynamics as a function of the thin film chemical composition. Furthermore, this study evaluates energetic disorder, carrier recombination rates, and non‐radiative losses for different compositions by extracting quantitative parameters such as Urbach energy and quasi‐Fermi level splitting, offering novel insights and guidelines for the design and optimization of emerging photovoltaic (PV) materials. Optimal PV performance metrics are achieved with a wide bandgap bromine perovskite containing 14% chlorine, striking a balance between morphology, transparency, and voltage losses.

Thermal transport in metal halide perovskites and other third-generation photovoltaic materials

Third-generation photovoltaic materials, including metal halide perovskites (MHPs), colloidal quantum dots (QDs), copper zinc tin sulfide (CZTS), and organic semiconductors, among others, have become attractive in the past two decades. Unlike their first- and second-generation counterparts, these advanced materials boast properties beyond mere photovoltaic performance, such as mechanical flexibility, light weight, and cost-effectiveness. Meanwhile, these materials possess more intricate crystalline structures that aid in understanding and predicting their transport properties. In particular, the distinctive phonon dispersions in MHPs, the layered architecture in quasi-two-dimensional (2D) perovskites, the strong quantum confinement in QDs, and the complex crystal structures interspersed with abundant disorders in quaternary CZTS result in unique and sometimes anomalous thermal transport behaviors. Concurrently, the criticality of thermal management in applications such as photovoltaics, thermoelectrics, light emitting diodes, and photodetection devices has received increased recognition, considering that many of these third-generation photovoltaic materials are not good thermal conductors. Effective thermal management necessitates precise measurement, advanced modeling, and a profound understanding and interpretation of thermal transport properties in these novel materials. In this review, we provide a comprehensive summary of various techniques for measuring thermal transport properties of these materials and discuss the ultralow thermal conductivities of three-dimensional (3D) MHPs, superlattice-like thermal transport in 2D perovskites, and novel thermal transport characteristics inherent in QDs and CZTS. By collecting and comparing the literature-reported results, we offer a thorough discussion on the thermal transport phenomenon in these materials. The collective understanding from the literature in this area, as reviewed in this article, can provide guidance for improving thermal management across a wide spectrum of applications extending beyond photovoltaics.

Advancing Solar Power Efficiency: Innovations in Material Science and System Optimization for Enhanced Solar Energy Conversion

This study aims to advance solar power efficiency through innovations in material science, surface engineering, and system optimization. The research integrates experimental testing and computational modeling to assess improvements in energy conversion efficiency. The methodology includes testing photovoltaic materials such as perovskite and multi-junction cells, anti-reflective coatings, self-cleaning surfaces, and optimizing panel orientation, cooling systems, and Maximum Power Point Tracking (MPPT) algorithms. Perovskite cells demonstrated a 22% increase in efficiency, while multi-junction cells achieved up to 35% efficiency. Anti-reflective coatings and self-cleaning surfaces improved energy capture by 4% and 7%, respectively. System optimization, including dual-axis trackers and AI-enhanced MPPT algorithms, provided additional efficiency gains of up to 25% and 10%, respectively. These findings demonstrate significant advancements in solar panel performance, providing a clear path for enhancing scalability and commercial viability in diverse environmental conditions. The integration of innovative materials and system optimizations presents a promising solution for making solar energy more sustainable and cost-effective. Future research should focus on improving the durability and reducing the costs of these technologies for widespread adoption.

First principles study of point defects and Li doping on the electronic structure and photovoltaic performance of single-layer GaN

The preparation of single-layer GaN by chemical vapor deposition inevitably generates H interstitials. In this study, the optical properties of single-layer Ga36N36, Ga34LiN36 and Ga34HiLiN36 (0 0 1) surfaces were investigated by using the first-principles method. In the presence of Li doping and H interstitial, the dielectric function and reflectivity red-shifted in the low-energy range and the dielectric function and reflectivity of the Ga36N36 improved. In the visible range of the absorption spectrum, the impurity-containing surfaces red-shifted, and the light absorption on the Ga36N36 improved. The Ga34HiLiN36 (0 0 1) surface performed better as a photovoltaic material than other surfaces.

Chemically functionalized diamanes - A new class of hybrid 2D materials: DFT insight into crystal, mechanical, and electronic properties

This work describes crystal and electronic structures of a new class of 2D hybrid organic-inorganic compounds based on AB-stacked diamane. Seven members thereof are considered: methyl-, pyrrolyl-, 1,2,4-triazolyl-, phenyl-, pyridinyl-, and pyrimidinyl-substituted (two isomers) diamane. DFT calculations show that an electronic structure of diamane can be modulated by organic functional groups. The chemically functionalized diamanes are semiconductors with HSE06 electronic bandgaps falling in the range [2.09–4.91] eV. Other means of diamane electronic structure tuning include variation of coverage of a diamane surface by substituents, mixing of substituents and changing their mutual orientation. Based on the obtained results we conclude that the functionalized diamanes may serve as photovoltaic materials operable in Vis and near UV spectral regions. Owing to a similarity of the aromatics-substituted diamanes to low-dimensional hybrid metal halide perovskites with aromatic organic cations the former could be photoluminescent. An enhanced resistance of the investigated materials to water is expected.

Influence of Substrate on Sb2Se3/CdS Heterojunction Thin Film Solar Cells and Evaluation of Their Performance by Dark J‐V Analysis

ABSTRACTA simple binary antimony selenide (Sb2Se3) absorber is evolving as an alternative photovoltaic material in thin film solar cells because of its unique properties and easy processing. Sb2Se3 thin films having good crystalline quality are grown via versatile thermal evaporation from pre‐synthesized near stoichiometric compound material on molybdenum‐coated soda lime glass (SLG) and borosilicate glass (BG) substrates. Following the systematic characterizations on the absorber films, substrate configured Sb2Se3/CdS heterojunction devices were fabricated and their photovoltaic characteristics have been studied using current density vs. voltage (J‐V), dark J‐V modeling, external quantum efficiency and capacitance vs. voltage measurements. The power conservation efficiency values of 4.88% and 5.04% were achieved for the devices fabricated on SLG and BG substrates, respectively with deficit in open circuit voltage. The obtained values are higher in comparison to the reported device efficiencies in substrate configured Sb2Se3 solar cells, in which the absorber is prepared through thermal evaporation. To understand the loss in open circuit voltage, a compact equivalent circuit model was considered and identified the contribution of different shunt leakage paths in the devices. In addition to that, the device fabricated on the SLG was stable with minimal changes in its photovoltaic performance for a period spanning over 200 days. The results obtained are encouraging with scope for improving the device performance through interface engineering and back surface passivation strategies.

Formamidinium Incorporates into Rb-based Non-perovskite Phases in Solar Cell Formulations.

Organic-inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI3), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non-perovskite phase complicates the application of FAPbI3in solar cells. To remedy this, alkali metal cations, most often Cs+, Rb+or K+, are included during perovskite synthesis to stabilize the photoactive phase. The atomic-level mechanisms of stabilization are complex. While Cs+dopes directly into the perovskite lattice, Rb+does not, but instead forms an additional non-perovskite phase, and the mechanism by which Rb confers increased stability remains unclear. Here, we use1H-87Rb double resonance NMR experiments to show that FA+incorporates into the Rb-based non-perovskite phases (FAyRb1-yPb2Br5andδ-FAyRb1-yPbI3) for both bromide and iodide perovskite formulations. This is demonstrated by changes in the1H and87Rb chemical shifts,1H-87Rb heteronuclear correlation spectra, and87Rb{1H} REDOR spectra. Simulation of the REDOR dephasing curves suggests up to ~60% FA+incorporation into the inorganic Rb-based phase for the bromide system. In light of these results, we hypothesize that the substitution of FA+into the non-perovskite phase may contribute to the greater stability conferred by Rb salts in the synthesis of FA-based perovskites.

Formamidinium Incorporates into Rb‐based Non‐perovskite Phases in Solar Cell Formulations

Organic–inorganic hybrid perovskite materials, such as formamidinium lead iodide (FAPbI3), are among the most promising emerging photovoltaic materials. However, the spontaneous phase transition from the photoactive perovskite phase to an inactive non‐perovskite phase complicates the application of FAPbI3 in solar cells. To remedy this, alkali metal cations, most often Cs+, Rb+or K+, are included during perovskite synthesis to stabilize the photoactive phase. The atomic‐level mechanisms of stabilization are complex. While Cs+ dopes directly into the perovskite lattice, Rb+ does not, but instead forms an additional non‐perovskite phase, and the mechanism by which Rb confers increased stability remains unclear. Here, we use 1H–87Rb double resonance NMR experiments to show that FA+ incorporates into the Rb‐based non‐perovskite phases (FAyRb1‐yPb2Br5 and δ‐FAyRb1‐yPbI3) for both bromide and iodide perovskite formulations. This is demonstrated by changes in the 1H and 87Rb chemical shifts, 1H–87Rb heteronuclear correlation spectra, and 87Rb{1H} REDOR spectra. Simulation of the REDOR dephasing curves suggests up to ~60% FA+ incorporation into the inorganic Rb‐based phase for the bromide system. In light of these results, we hypothesize that the substitution of FA+ into the non‐perovskite phase may contribute to the greater stability conferred by Rb salts in the synthesis of FA‐based perovskites.

Structural Modeling of Fluorinated Quinoxaline Core–Based Chromophores for Efficient Photovoltaic Materials: A DFT Study

ABSTRACTHerein, a series of fluorinated quinoxaline core–based chromophores (MTH1‐MTH6) with A1–π–A2–π–A1 configuration was designed by structural modulation of end‐capped acceptors in MTHR. The quantum chemical calculations were accomplished at MPW1PW91/6‐311G(d,p) functional to explore optoelectronic and photovoltaic properties of these designed compounds. The findings revealed that all the derivatives exhibited narrow band gap (Egap = 2.163–2.666 eV) with red shift spectra (610.24–766.944 eV in chloroform) as compared with MTHR. The designed compounds exhibited comparable open‐circuit voltage (Voc) and higher power conversion efficiencies (PCEs) as compared with the MTHR. Among the entitled chromophores, MTH1 was found to be a promising chromophore for organic solar cells (OSCs) owning to its lowest Egap (2.163 eV) with highest absorption peak (766.944 nm in chloroform and 717.709 nm in gaseous phase). The aforementioned findings indicate that molecular engineering of chromophores with extended acceptors enhances photovoltaic response, and this motivates researchers to develop highly effective photovoltaic devices.

Enhancing thermoelectric and radiation shielding performance of novel LaFe0.8Mn0.2Sb12 skutterudites for energy applications

We explore the structural, optoelectronic, and thermoelectric properties of LaFe0.8Mn0.2Sb12 skutterudites using first-principles computations and semi-classical Boltzmann Transport equations. These materials are classified as semiconductors exhibiting band gaps of 0.55 eV and 1.8 eV for spin-up and down polarizations. Valence band maxima (VBM) and conduction band minima (CBM) lie on the gamma points, indicating direct band gaps for both spin channels. The band structure, density of states, and optical characteristics reveal that the material is a semiconductor. The optical reflectivity and complex dielectric function were calculated for a wide range of photon radiation to understand these compounds' optical properties. The transport parameters were investigated using electrical conductivity, thermal conductivity, the Seebeck coefficient, the power factor, the heat capacity, and the figure of merit determined using the Boltztrap code. The LaFe0.8Mn0.2Sb12 has a Seebeck coefficient of 5.77×10−6 V/K (Up), whereas the down channel has a 4.2×10−6 V/K. The highest figure of merit is 0.99, and as a result, the theoretical findings provide a robust foundation for upcoming experimental research. In this study, utilize the Phy-X program to evaluate the radiation shielding capabilities of LaFe0.8Mn0.2Sb12, focusing on critical parameters like mass attenuation coefficients (γmac) and half-value layers (γhvl), essential for optimizing protection against hazardous ionizing radiation. Computational study of energy-renewable and thermoelectric properties enables experimenters to investigate fresh applications for predicting photovoltaic materials with atomic-level accuracy.