Solar Cell Materials Research Articles

Constraining the Excessive Aggregation of Non-Fullerene Acceptor Molecules Enables Organic Solar Modules with the Efficiency >16.

Translating high-performance organic solar cell (OSC) materials from spin-coating to scalable processing is imperative for advancing organic photovoltaics. For bridging the gap between laboratory research and industrialization, it is essential to understand the structural formation dynamics within the photoactive layer during printing processes. In this study, two typical printing-compatible solvents in the doctor-blading process are employed to explore the intricate mechanisms governing the thin-film formation in the state-of-the-art photovoltaic system PM6:L8-BO. Our findings highlight the synergistic influence of both the donor polymer PM6 and the solvent with a high boiling point on the structural dynamics of L8-BO within the photoactive layer, significantly influencing its morphological properties. The optimized processing strategy effectively suppresses the excessive aggregation of L8-BO during the slow drying process in doctor-blading, enhancing thin-film crystallization with preferential molecular orientation. These improvements facilitate more efficient charge transport, suppress thin-film defects and charge recombination, and finally enhance the upscaling potential. Consequently, the optimized PM6:L8-BO OSCs demonstrate power conversion efficiencies of 18.42% in small-area devices (0.064 cm2) and 16.02% in modules (11.70 cm2), respectively. Overall, this research provides valuable insights into the interplay among thin-film formation kinetics, structure dynamics, and device performance in scalable processing.

Bandgap Engineering via Doping Strategies for Narrowing the Bandgap below 1.2 eV in Sn/Pb Binary Perovskites: Unveiling the Role of Bi3+ Incorporation on Different A-Site Compositions.

The integration of perovskite materials in solar cells has garnered significant attention due to their exceptional photovoltaic properties. However, achieving a bandgap energy below 1.2 eV remains challenging, particularly for applications requiring infrared absorption, such as sub-cells in tandem solar cells and single-junction perovskite solar cells. In this study, we employed a doping strategy to engineer the bandgap and observed that the doping effects varied depending on the A-site cation. Specifically, we investigated the impact of bismuth (Bi3+) incorporation into perovskites with different A-site cations, such as cesium (Cs) and methylammonium (MA). Remarkably, Bi3+ doping in MA-based tin-lead perovskites enabled the fabrication of ultra-narrow bandgap films (~1 eV). Comprehensive characterization, including structural, optical, and electronic analyses, was conducted to elucidate the effects of Bi doping. Notably, 8% Bi-doped Sn-Pb perovskites demonstrated infrared absorption extending up to 1360 nm, an unprecedented range for ABX3-type single halide perovskites. This work provides valuable insights into further narrowing the bandgap of halide perovskite materials, which is essential for their effective use in multi-junction tandem solar cell architectures.

Monosilicon Derivatives of Phenanthrene and Pyrene as Potential Singlet Fission Materials for High-Performance Solar Cells.

Singlet fission (SF) is a process in which the energy of a singlet-excited molecule is divided into two triplet excitations. This is a special case of an internal conversion that is spin-allowed and extremely fast. Ideally, this process utilizes one photon to produce two electron-hole pairs. In tandem with a layer of singlet fission material, conventional solar cells can achieve improved efficiency by utilizing higher-energy photons. This density functional theory study provides information about additional efficient SF chromophores that were theoretically modeled by functionalizing phenanthrene and pyrene via site-specific monosilicon substitutions. The SF capabilities of the derivatives were evaluated by calculating the SF thermodynamic driving force (ΔESF) and the excited state's molecular planarity. The most promising monosilicon derivatives with SF capabilities are 3-silaphenanthrene and 1-silapyrene for each family, respectively. All phenanthrene and pyrene monosilicon derivatives are strong closed-shell species, because their multiple diradical characteristics are close to zero. Based on these results, 3-silaphenanthrene and 1-silapyrene were selected for electron excitation analysis, which further demonstrated that the monosilicon functionalization of phenanthrene and pyrene led to a transfer from local excitation characters to hybridized local and charge-transfer characters of the excited states, resulting in a significant change from endoergic to exoergic in the SF chromophores.

Trends Research Synthesis of TiO2 Thin Films as Solar Cell Materials (2015-2024): A Systematic Review

Research in the field of solar cells continues to increase along with the development of the times and human needs for renewable energy sources. One of the fields of study that is often used as a research topic is the development of Thin Film Solar Cells or known as Thin Film Solar Cells (TFSC). This research aims to identify and analyze research trends of synthesis of TiO2 thin films as solar cell materials. This research method is descriptive and analytical. The data used in this research was obtained from documents indexed by Google Scholar from 2015-2024 using Publish or Perish and Dimension.ai. Research procedures use PRISMA guidelines. The data identified and analyzed are the type of publication, publication source, and the title of research on synthesis of Ti02 thin films as solar cell materials that is widely cited. The data analysis method uses bibliometric analysis assisted by VOS viewer software. The results of the analysis show that research trend on synthesis of TiO2 thin films as solar cell materials indexed by Google Scholar from 2015 to 2024 has experienced increases and decreases. There are many documents in the form of articles, proceedings, chapters, preprints, monograph and edited books that discuss research about synthesis of TiO2 thin films as solar cell materials. Key words that are often used in research about it are dye sensitized cell, electrode, electron, characterization, etc.

Light-Induced Metallic and Paramagnetic Defects in Halide Perovskites from Magnetic Resonance.

Halide perovskites are promising next-generation solar cell materials, but their commercialization is hampered by their propensity to degrade under operating conditions, particularly under heat, humidity, and light. Identifying degradation products and linking them to the degradation mechanism at the atomic scale is necessary to design more stable perovskite materials. Here we use magnetic resonance methods to identify and characterize the formation of both metallic lead clusters and Pb3+ defects upon light-induced degradation of methylammonium lead halide perovskite using nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) measurements. Paramagnetic relaxation enhancement (PRE) of the 1H NMR resonances demonstrates the presence of localized paramagnetic Pb3+ defects, a large Knight shift of the 207Pb NMR proves the presence of lead metal, and their relative proportions are determined by the differing temperature dependence in variable-temperature EPR. This work reconciles previous conflicting literature results, enabling the use of EPR spectroscopy to monitor photodegradation of perovskite devices.

Formation of High-Photoresponsivity BaSi2 Films by Radio-Frequency Sputtering and Evaluation of a BaSi2/TiN/Glass Heterojunction by Transmission Electron Microscopy.

Barium disilicide (BaSi2) is a thin-film solar cell material composed of abundant elements, and its application potential is further enhanced by its formation on inexpensive substrates, such as glass. The effect of the substrate temperature on the co-sputtering of BaSi2 and Ba targets to form BaSi2 films on Si(111) and TiN/glass substrates was investigated. Contrary to expectations, the photoresponsivity reached maximum values exceeding 5 and 2 A W-1, respectively, the highest value ever reported for as-deposited samples formed at 750 °C, more than 100 °C higher than those reported previously. Because the photoresponsivity is proportional to carrier lifetime, this result indicates that high-temperature growth can bring out the high performance of BaSi2 as a light-absorbing layer. Because amorphous SiC (a-SiC) has a larger forbidden band gap and electron affinity than BaSi2, it is considered suitable as an electron transport layer (ETL) material for BaSi2 solar cells. On the basis of this, the formation of BaSi2 (absorption layer)/a-SiC (ETL)/TiN (electrode)/glass heterojunctions was also attempted, and the layered structure was examined by cross-sectional transmission electron microscopy (TEM). Polycrystalline BaSi2 films were found to be even on the amorphous layer by TEM. A high photoresponsivity of over 2 A W-1 was obtained. Therefore, the BaSi2/a-SiC/TiN structure provides a guideline for the structural design of BaSi2-based thin-film solar cells on glass.

Enhanced Design of Kesterite Solar Cells through High-Throughput Screening and Machine Learning Approaches.

Kesterite Cu2ZnSnS4 (CZTS) is regarded as one of the most promising materials for thin-film solar cells due to its high light absorption capability, composition of earth-abundant and nontoxic elements, and ease of low-cost mass production. Although the certified power conversion efficiency (PCE) of kesterite solar cells has exceeded 14%, this efficiency remains significantly below the Shockley-Queisser limit. In this study, we generated a Perdew-Burke-Ernzerhof (PBE) band gap data set encompassing 263 64-atom species for high-throughput screening by substituting elements at different sites in A2BCX4 quaternary kesterite materials. Additionally, we utilized a symbolic regression method based on genetic programming to explore the functional relationship among the oxidation state, ionic radius, and electronegativity of kesterites with PBE band gaps. Simultaneously, we employed decision tree models (XGBoost, LightGBM, CatBoost, and random forest) and convolutional neural network (CNN) models (CustomCNN, VGG16, DenseNet121, Xception, and EfficientNetV2B0) to predict band gaps, achieving a coefficient of determination (R2) of up to 0.93. Furthermore, we selected 54 kesterite materials with PBE band gaps ranging from 0.4 to 1.5 eV for detailed electronic structure calculations with Heyd-Scuseria-Ernzerhof (HSE06) functional and investigated the effects of B-site atomic substitutions on the performance of solar cell materials. Compared to Ag2CaSnSe4, Ag2SrSnSe4 exhibits fewer deep defects and richer shallow defects, which contribute to an increased carrier concentration and reduced charge and energy losses, making it a superior candidate for solar cell applications.

Numerical simulation of lead-free MASnI3 perovskite/silicon heterojunction for solar cells and photodetectors

Lead free n-type doped methyl ammonium tin iodide (MASnI3) perovskite/p-Silicon heterojunction (HJ) for solar cells and photodetectors are simulated using AFORS-HET automat simulation software. In the earlier work, lead based methyl ammonium lead iodide perovskite/silicon (n-MAPbI3/p-Si) heterojunction devices were studied. In view of the toxicity and environmental concerns related to lead, it is substituted with tin to make lead-free tin based perovskite to make n-MASnI3/p-Si HJ devices. Various parameters associated with the layers of MASnI3 perovskite and silicon wafer like, Band gap, thickness, doping concentration and texturing angle have been optimized. Various transparent conducting oxide (TCO) materials like indium tin oxide (ITO) and zinc oxide (ZnO) are used and its performance with ideal device is compared. Various metals are considered as front and back contact, to obtain best metals for each sides. This study investigates the potential of lead-free perovskite materials in solar cells, achieving a notable efficiency improvement compared to traditional lead-based counterparts. Our numerical simulations demonstrate that the optimized lead-free perovskite with structures, n-MASnI3/p-Si heterojunction can reach efficiencies of 27.2%. These findings suggest that lead-free perovskites could serve as a viable, environmentally friendly alternative in the photovoltaic industry.

Tailoring Diversified Peripheral Anchor Groups in Spirofluorene‐Dithiolane‐Based Hole Transporting Materials for Efficient Organic and Perovskite Solar Cells from First‐Principle

AbstractThis quantum mechanical approach recommends push–pull molecular engineering to fabricate hole‐transporting materials (HTMs) for photovoltaic cells. It integrates acceptor moieties via thiophene to fluorene core, resulting in five novel HTMs (SFD‐1 to SFD‐5). The results exhibit that derivative HTMs show excellent coherence in excitation, dispersion, and transportation of charge carriers, ensuring robust hole mobility. The anchor moieties functionalized HTMs unveil excellent band alignment with perovskite with fitting HOMO energy levels (−4.93–−5.35 eV), less optical absorption in visible portion ( < 520). This acceptor integration has improved the hole mobility in derivatives, accredited to the smaller hole reorganization energy (0.14–0.68 eV), and greater hole transfer integral (0.22–0.33 eV). The transition density matrix analysis exhibited robust electronic coupling, subtler charge carrier overlapping and greater charge transfer length (7.48–13.73 Å). This resulted in an excellent upsurge in intrinsic charge transference (70.75–92.70%) and smaller exciton binding energy, leading to easier exciton dissociation, and fewer recombination fatalities. However, an adequate variation in dipole moment (4.04 D to 16.34 D) and Gibbs solvation‐free energy (−18.06 to −21.89 kcal mol−1) ensures facile film formation and processability. In conclusion, this approach recommends these flourene‐based HTMs are highly desireable for forthcoming solar cell technology.

Extending the defect tolerance of halide perovskite nanocrystals to hot carrier cooling dynamics

Defect tolerance is a critical enabling factor for efficient lead-halide perovskite materials, but the current understanding is primarily on band-edge (cold) carriers, with significant debate over whether hot carriers can also exhibit defect tolerance. Here, this important gap in the field is addressed by investigating how intentionally-introduced traps affect hot carrier relaxation in CsPbX3 nanocrystals (X = Br, I, or mixture). Using femtosecond interband and intraband spectroscopy, along with energy-dependent photoluminescence measurements and kinetic modelling, it is found that hot carriers are not universally defect tolerant in CsPbX3, but are strongly correlated to the defect tolerance of cold carriers, requiring shallow traps to be present (as in CsPbI3). It is found that hot carriers are directly captured by traps, instead of going through an intermediate cold carrier, and deeper traps cause faster hot carrier cooling, reducing the effects of the hot phonon bottleneck and Auger reheating. This work provides important insights into how defects influence hot carriers, which will be important for designing materials for hot carrier solar cells, multiexciton generation, and optical gain media.

Highly reliable anti-reflection radiative cooling glass applicable to thermal management of solar cells

The encapsulation materials of solar cells have a significant impact on the performance and stability of the cells. Herein, an anti-reflection radiative cooling (ARRC) glass for photovoltaic (PV) devices is proposed by multi-layer design. Harnessing the synergy of anti-reflection layers and a transparent radiative cooling layer, ARRC glass can dissipate heat radiatively through molecular vibrations. Concurrently, it maintains the functionality and aesthetics of the associated devices. ARRC possesses four prominent characteristics, enabling it to serve as an encapsulation glass to enhance the performance and stability of solar cells. 1. Superior maximum visible light transmittance (0.954, 602 nm). 2. Outstanding mid-infrared emittance (0.951). 3. Excellent UV blocking performance (reached 99 % at 320 nm). 4. Marvelous thermal management performance (6.6 °C cooling for multi-crystalline silicon solar cells and 8.6 °C cooling for perovskite cells). Excellent anti-reflection and cooling performance of ARRC glass improves conversion efficiency by 1.08 % and 1.79 % for multi-crystalline silicon solar cells and perovskite solar cells (PSCs), respectively. Moreover, ARRC glass enhances the UV stability of PSCs by 4 times and significantly alleviates the thermal decomposition of PSCs. The ARRC glass, with excellent adhesion, scalability, economy, and stability, is expected to be applied on a large scale and further contribute to energy and environment sustainability.

Influence of sulfurization temperature on grain growth in Cu2ZnSnS4 thin films synthesized for solar cell applications

Copper-zinc-tin-sulfur (CZTS) thin films, prepared through a dip-coating solution method, present a highly attractive option as absorber materials for thin-film solar cells. This is due to their affordability, environmentally friendly composition, and abundant availability of raw materials. Although films processed with hydrazine-based solutions have achieved the highest efficiency of approximately 12.6%, the toxic and carcinogenic nature of hydrazine negates these advantages. In the ongoing global research on solution-based processing methods, the size of the grains has emerged as a critical factor in the fabrication of efficient solar cells. In our study, we have successfully prepared CZTS thin films with a pure kesterite phase, characterized by large micro-sized grains, using a dip-coating process with an ethanol-based precursor solution, followed by sulfurization. We investigated how the grain size evolves with varying sulfurization temperatures. Notably, we observed that increasing the temperature led to larger and more uniform grain growth. These results underscore the potential of our approach for the straightforward production of high-quality films with sizable grains, ultimately enhancing their photosensitivity and making them a promising candidate for efficient solar cell applications.

Direction Modulation of Intramolecular Electric Field Boosts Hole Transport in Phthalocyanines for Perovskite Solar Cells.

Tuning the strength of intramolecular electric field (IEF) in conjugated molecules has emerged as an effective approach to boost charge transfer. While direction manipulation of IEF would be a potential way that is still unclear. Here, we leverage the control of peripheral substituents of conjugated phthalocyanines to chemically tune the spatial orientation of IEF. By analyzing the spatial swing of side chains using the Kolmogorov-Arnold representation and least squares algorithm, a comprehensive mathematical-physical model has been established. This model enables rapid evaluation of the IEF and maximum hole transport performance induced by spatial swings. The champion phthalocyanine as dopant-free hole transport material in perovskite solar cell realizes a record performance of 23.41%. Greatly device stability is also exhibited. This work affords a new way to enhance hole transport capabilities of conjugated molecules by optimizing their IEF vector for photovoltaic devices.

Interface Engineering by Unsubstituted Pristine Nickel Phthalocyanine as Hole Transport Material for Efficient and Stable Perovskite Solar Cells.

Lead halide perovskite solar cells (PSCs) have been rapidly developed in the past decade. With the development of a PSC, interface engineering plays an increasingly important role in maximizing device performance and long-term stability. We report a simple and effective interface engineering method for achieving improvement of PSCs up to 20% by employing unsubstituted pristine nickel phthalocyanine (NiPc). Thermal annealing of NiPc improves the interface between NiPc and perovskite because of the incorporation of NiPc molecules into the perovskite grain boundaries, which creates improvements in hole extraction from the perovskite absorber layer, as evidenced by time-resolved photoluminescence measurements. This significantly improves the charge transfer and collection efficiency, which are closely related to the improvement of the interface between perovskite and NiPc.

Direction Modulation of Intramolecular Electric Field Boosts Hole Transport in Phthalocyanines for Perovskite Solar Cells

Tuning the strength of intramolecular electric field (IEF) in conjugated molecules has emerged as an effective approach to boost charge transfer. While direction manipulation of IEF would be a potential way that is still unclear. Here, we leverage the control of peripheral substituents of conjugated phthalocyanines to chemically tune the spatial orientation of IEF. By analyzing the spatial swing of side chains using the Kolmogorov‐Arnold representation and least squares algorithm, a comprehensive mathematical‐physical model has been established. This model enables rapid evaluation of the IEF and maximum hole transport performance induced by spatial swings. The champion phthalocyanine as dopant‐free hole transport material in perovskite solar cell realizes a record performance of 23.41%. Greatly device stability is also exhibited. This work affords a new way to enhance hole transport capabilities of conjugated molecules by optimizing their IEF vector for photovoltaic devices.

Tuning of optical, thermodynamic, and thermoelectric properties of Cs2CuBiX6 (X = Cl, Br, I) halide perovskites for solar cells and energy harvesting applications

The double perovskites are outstanding materials for solar cells and transport applications to clean harvest energy. Therefore, the Cs2CuBiX6 (X = Cl, Br, I) are discussed comprehensively for energy harvesting by modified Becke and Johnson (mBJ) potential. The studied DPs fit the structural, mechanical, and dynamic stability scale by tolerance factor, Born–Huang criteria, and phonon dispersion band structures. The band gaps (1.20, 1.0, 0.70) eV for (Cl, Br, I) based DPs ensure the Cs2CuBiCl6 has an absorption band in the visible region while Cs2CuBiBr6 and Cs2CuBiI6 has an absorption band in the infrared region. Heavy elements’ spin–orbit coupling effect (Cs, Bi) reduces the band gap to 0.08 eV. Thermoelectric behavior regarding the merit scale against dopant carriers and temperature has been elaborated. The ultralow lattice thermal conductivity, large Debye temperature, hardness, and melting temperature increase their implication for thermoelectric and other thermodynamic applications. The variation in band gap makes them important for diverse optoelectric and thermoelectric applications. The Cs2CuBiCl6 with a band gap of 1.20 eV is suitable for solar cells, while Cs2CuBiBr6 and Cs2CuBiI6 with band gaps of 1.0 eV and 0.70 eV are significant for thermoelectric generators.

The impact of halogens on the structural, electronic, and optical properties of vacancy-ordered double perovskites Rb2SeX6 (X=I, Br, Cl)

Lead-based perovskite materials have become one of the most widely used materials in the field of photovoltaics due to their excellent properties. However, concerns over lead toxicity and the stability of materials have prompted the search for alternative, eco-friendly, and stable perovskite materials. To address this need, our study conducts an in-depth analysis of the electronic and optical properties of the lead-free double perovskite materials Rb2SeX6 (X = Cl, Br, I) using first-principles calculations. The results indicate that Rb2SeX6 perovskites possess an indirect bandgap, with values of 3.26 eV, 2.52 eV and 1.39 eV for Rb2SeCl6/Br6/I6, respectively. Rb2SeI6 has larger dielectric function and superior absorption spectrum across the visible range than the other two materials. Thus, Rb2SeI6 has a promising future as a photoelectric material for solar cells. Rb2SeCl6 and Rb2SeBr6 also have the potential for use in photodetectors, light-emitting diodes and other optoelectronic devices.

Preparation and performance study of organic small molecule photovoltaic donor materials in solar cells

Abstract In this study, PDPAT-BDT-BT was used as a donor material, combined with PC61BM and PC71BM as acceptor materials, to prepare a hybrid thin film for organic solar cells. In photovoltaic performance tests, this film shows advantages and good characteristics. The experimental results show that the PDPAT-BDT-BT polymer shows good performance in terms of thermal stability, optical properties, and electrochemical properties. It also shows better photovoltaic performance in the hybrid system with PC71BM, which lays a good foundation for its potential application in organic solar cells.

Near Room Temperature Solvothermal Growth of Ferroelectric CsPbBr3 Nanoplatelets with Ultralow Dark Current.

CsPbBr3 exhibits outstanding optoelectronic properties and thermal stability, making it a coveted material for detectors, light-emitting diodes, and solar cells. Despite observations of ferroelectricity in CsPbBr3 quantum dots, synthesizing bulk ferroelectric CsPbBr3 crystals has remained elusive, hindering its potential in next-generation optoelectronic devices like optical switches and ferroelectric photovoltaics. Here, a breakthrough is reported: a novel solvothermal technique enabling the growth of ferroelectric CsPbBr3 nanoplatelets with lateral dimensions in the tens of micrometers. This represents a significant step toward achieving large-area ferroelectric CsPbBr3 crystals. Unlike traditional methods, this approach allows for growth and crystallization of CsPbBr3 in alcohol solutions by enhancing precursor solubility. This study confirms the ferroelectric nature of these nanoplatelets using second harmonic generation, electrical characterizations, and piezoresponse force microscopy. This work paves the way for utilizing ferroelectric CsPbBr3 in novel optoelectronic devices, significantly expanding the potential of this material and opening doors for further exploration in this exciting field.

Numerical optimization of lead-based and lead-free absorber materials for perovskite solar cell (PSC) architectures: A SCAPS-1D simulation

Numerical optimization of lead-based and lead-free absorber materials for perovskite solar cell (PSC) architectures: A SCAPS-1D simulation