Photovoltaic Materials Research Articles

Synthesis and simulation study of titanium dioxide-based nanomaterial for electron carrier selective contact solar cell

This research introduces a novel approach to synthesizing titanium dioxide (TiO2) nanomaterials using the sol–gel method, specifically aimed at enhancing the performance of Silicon Heterojunction (SHJ) solar cells. The innovation lies in utilizing Iso-Propanol Alcohol and Titanium Tetra Isopropoxides for synthesis, leveraging TiO2’s wide bandgap and low work function to replace the conventional n-doped amorphous silicon layer. This approach is expected to overcome the limitations of traditional materials and significantly improve electron transport efficiency. Advanced characterization techniques were employed to assess the synthesized TiO2 nanomaterials. Atomic Force Microscopy (AFM) measured the roughness and 3D profile, while UV-V spectrophotometry evaluated the absorption properties. The structure and surface morphology were meticulously analyzed using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). These comprehensive analyses ensured a detailed understanding of the nanomaterials’ physical properties. Simulations conducted with the AFORS-HET simulator revealed that TiO2, with a refractive index compatible with a-Si:H(n) and a work function of 4.6 eV, significantly enhances SHJ solar cell performance. The results demonstrated a remarkable 22.57 % improvement in efficiency, achieving an open-circuit voltage (Voc) of 716.8 mV, a short-circuit current density (Jsc) of 37.71 mA/cm2 and a fill factor (FF) of 83.49 %. These findings underscore the potential of TiO2 nanomaterials to revolutionize SHJ solar cell technology by providing a more efficient and effective electron transport layer. Future research will focus on refining the nanostructure of TiO2 further to enhance its photovoltaic applications, aiming to push the boundaries of current solar cell efficiencies even further. This study marks a significant advancement in the field of photovoltaic materials, presenting a novel and promising solution to improving solar energy conversion.

(Invited) Semi-Monolithically Integrated Photoelectrochemical Devices for Unassisted Water Splitting

Photoelectrochemical (PEC) water splitting has the potential to become an efficient method for renewable hydrogen production. However, the efficiency, projected cost, and durability of lab-scale systems are not yet at the level required to make this technology economically feasible. Amongst all materials studied to date, the chalcopyrite class is arguably one of the most promising classes for PEC water splitting, as it has already demonstrated low-cost and high photoconversion capabilities as a photovoltaic material. In the context of PEC, our group demonstrated that co-evaporated 1.65 eV bandgap (EG) CuGaSe2 is capable of evolving hydrogen with Faradaic efficiency greater than 85% and generate photocurrent densities over 15 mA.cm-2, as measured in a 3-electrode configuration in 0.5M H2SO4 under simulated AM1.5G illumination. Unfortunately, CuGaSe2’s narrow EG limits its integration as top absorber into multi-junction stacked PEC device. In the present communication, we report on our latest efforts to synthesize wide-EG (1.8-2.0 eV) chalcopyrites compatible with the stacked multi-junction integration scheme. We present specifically results on EGtunable Cu(In,Ga)S2, CuGa(S,Se)2 and order vacancy compound CuGa3Se5. We also discuss some of the strategies developed to improve their surface energetics for the hydrogen evolution reaction, including the use of bandgap tunable MgZnO n-type buffer layers. Finally, we introduce the concept of semi-monolithic tandems, a new integration scheme where wide- and narrow-bandgap chalcopyrites are first integrated on separate substrates, then exfoliated, and finally bonded together to create fully functional multi-junction PEC devices.

(Invited) Parameter Prediction in Colloidal Quantum Dot Solar Cells Using Residual Neural Networks Trained on Experimental Data

Colloidal quantum dots (CQDs) are an attractive third-generation material for photovoltaics, especially as infrared materials for multi-junction solar cells. Characterization and materials parameter prediction both play a critical role in the rising efficiencies in this field. However, there are numerous materials properties that need to be measured in order to fully characterize a device, leading to high research costs and slow development times. Here, we leverage recent advancements in machine learning (ML), along with a recently-demonstrated multimodal spectral characterization method [1], to predict complex materials parameters in CQD solar cells from simple current density-voltage (JV) curves, using an algorithm trained on experimental data.[2]Past work ML prediction of materials properties has focused on using simulated data due to the difficulty in collecting enough experimental data to fully train an algorithm. While it is not feasible to fabricate thousands of devices in a typical research lab, it is possible to measure several thousand points on a single device. We used a micrometer-resolution 2D characterization method with millimeter-scale field of view to acquire enough training data using only a handful of devices, while learning the spatial relationships between materials parameters. Photoluminescence, trap state density, transient photovoltage, transient photocurrent, and carrier mobility were predicted (Figure 1) by five different residual neural networks, each using a ResNet block and containing over 300k learnable parameters. The design of the networks were based on the ResNet50 architecture [3]. We also implemented a novel neighborhood approach to reduce errors and account for spatial correlations in device behavior, leading to insights into transport mechanisms and correlation lengths in CQD thin films. This method could be used to study a wide range of material systems and devices, ultimately leading to a universal prediction model that greatly simplifies the characterization process for optoelectronic devices and accelerates development times.

(Invited) Forecasting Hybrid Perovskites’ Dynamic Response through Machine Learning

Machine learning (ML) can significantly accelerate the discovery of materials for clean energy. Hybrid perovskites (an emerging class of materials for photovoltaics and light-emitting diodes) encompass an enormous chemical composition space, resulting in a hyperparameter space that is nearly impossible to be interrogated via traditional trial-and-error methods. Thus, there has been a pressing need within the materials research community to identify ML models that can be implemented to inform the physical and chemical behavior of the perovskites. Here, we apply distinct ML models (mostly based on recurrent neural networks) to classify and forecast physical properties encompassing electrical conductivity, photoluminescence response, the power conversion efficiency of photovoltaic devices, etc. Specifically, we use automated, in situ optical measurements to predict the optical response of a series of perovskites for 50+ hours, upon materials’ exposure to moisture. We quantitatively compare linear regression, echo state network, and seasonal auto-regressive integrated moving average with eXogenous regressor algorithms and achieve accuracy of >90% for the latter. Demonstrating the ability of this model to capture non-linear features. Our high-throughput measurements and ML-assisted data analysis exemplifies the potential of ML to diagnose and forecast hybrid perovskites’ response with a variety of chemical compositions.

Distinct High-Pressure Responses of Halide Perovskites from Bulk to Low Dimension

Hybrid organic-inorganic perovskites (HOIPs) are low-cost and highly efficient optoelectronic and photovoltaic materials for applications in solar cells, light emitting diodes (LEDs), and so on, which is correlated with their intrinsic structures. Now the hybrid perovskite families include three-dimensional (3D) (CH3NH3PbBr3), two-dimensional (2D) ((C4H9NH3)2(CH3NH3)n-1PbnI3n+1) and nanostructured ((CH3NH3PbBr3 nanoparticles) materials. Herein, well understanding the relationship between the cystal structures and the related functional properties of HOIP materials is essential to the application point of view. High pressure up to gigapascal, offers a comprehensive way to study the structure-property correlation of solid materials in the atomic level, where both crystal structures and electronic properties are changed dramatically.In this presentation, high pressure induced dramatically inorganic and organic part changes in 2D HOIPs are comprehensively studied[1,2], as shown in Figure 1. On the other hand, structural phase transition and morphology changes are also explored in 3D HOIP and their nanoparticles[3], as shown in Figure 2. All the high pressure-induced inorganic structural transition is resolved by in situ X-ray powder diffraction (XRD) measurements, morphology change is resolved by transmission electron microscopy (TEM), the correlated optical responses are investigated by absorption and photoluminescence spectroscopy. And the rotational isomerism is evidenced by the vibrational properties of the organic BA chain by Raman spectroscopy combined with the Ab initio calculations.Reference:[1] T Yin, B Liu, J Yan, Y Fang, M Chen, WK Chong, S Jiang, J-L Kuo, J Fang, P L, S-H W, K-P Loh, T-C Sum, T J. White, and Z Xiang, J. Am. Chem. Soc. 141, 1235 (2019).[2] Yin T, Yan H, Abdelwahab I, Lekina Y, Lü X, Yang W, Sun H, Leng K, Cai Y, Shen Z, Loh KP, Nat. Commun. 14, 411 (2023).[3] T Yin, Y Fang, WK Chong, KT Ming, S Jiang, X Li, J-L Kuo, J Fang, T-C Sum, T J. White, J Yan, and Z Xiang, Adv. Mater. 30, 1705017 (2018). Figure 1

Contrasting Ultra-Low Frequency Raman and Infrared Modes in Emerging Metal Halides for Photovoltaics.

Lattice dynamics are critical to photovoltaic material performance, governing dynamic disorder, hot-carrier cooling, charge-carrier recombination, and transport. Soft metal-halide perovskites exhibit particularly intriguing dynamics, with Raman spectra exhibiting an unusually broad low-frequency response whose origin is still much debated. Here, we utilize ultra-low frequency Raman and infrared terahertz time-domain spectroscopies to provide a systematic examination of the vibrational response for a wide range of metal-halide semiconductors: FAPbI3, MAPbI x Br3-x , CsPbBr3, PbI2, Cs2AgBiBr6, Cu2AgBiI6, and AgI. We rule out extrinsic defects, octahedral tilting, cation lone pairs, and "liquid-like" Boson peaks as causes of the debated central Raman peak. Instead, we propose that the central Raman response results from an interplay of the significant broadening of Raman-active, low-energy phonon modes that are strongly amplified by a population component from Bose-Einstein statistics toward low frequency. These findings elucidate the complexities of light interactions with low-energy lattice vibrations in soft metal-halide semiconductors emerging for photovoltaic applications.

Computational Investigation of Structural, Electronic and Optical Properties of Ternary Chalcogenide TLGaQ2 Monoclinic Compounds: a First Principle Study

Purpose: This paper aim to investigate and predict by simulation the impact of the substitution of Q-site atom (Q꞊S, Se) on the TIGaQ2 monoclinic compounds for the first time, along the three main polarizations of the incident wave directions [100], [010] and [001]. Theoretical Framework: This study focuses mainly on ternary chalcogenide compounds TlGaQ2 (Q= S, Se) from ABQ2 family to highlight the objective resources aimed at promising prospects offered for them. Design/Methodology/Approach: A series of ab-initio calculations based on the (PW+PP) method within the density functional theory DFT framework were carried out with CASTEP code for the simulation of their physical properties (structural, electronic-optical). The exchange correlation potential was treated within the generalized gradient approximation (GGA) implemented in the CASTEP code and expressed by the PBE functional. Findings: The equilibrium lattice parameters are in good agreement with the available experimental results. The calculated band structure shows that are direct bandgap semiconductor nature 1.92eV (1.41eV) for TlGaS2 and TlGaSe2 respectively with a great potential for photovoltaic solar cell absorber materials. A set of optical parameters were calculated including the complex dielectric function, the reflective index, reflectivity, the absorption coefficient and loss function. The optical properties obtained revealed very interesting optical properties exhibiting strong optical absorption in UV range up to (~2x105cm-1) for both compounds making them appropriate for photovoltaic solar-cell absorber materials. Furthermore, low reflectivity and energy loss function are shown within in the visible and ultraviolet energy range, allowing them to be promising materials in several optoelectronics applications likes photosensitive devices. Implications: All these findings results show a successful accurately prediction for chalcogenide materials behavior and will be helpful for future studies allowing a better understanding of their potential applications in modern photovoltaic technologies as well as within UV ranges for optoelectronics applications.

Ab Initio Study of Structural, Electronic, Optical, and Thermoelectric Properties of Cs2(Li/Na)GaI6 for Green Energy Applications

The recent year has witnessed a flurry of activities in investigating the promising electronic, optical, and transport properties of lead‐free double perovskite halides. In the present work, the structural, electronic, optical, and transport properties of Cs2(Li/Na)GaI6 are carefully examined. The predicted negative formation energy, absence of imaginary frequency in the phonon spectra, and ab‐initio molecular dynamics calculations show that they are thermodynamically stable. Additionally, electronic studies employing generalized gradient approximation (GGA)–Perdew–Burke–Ernzerhof (PBE) + modified Becke‐Johnson + spin‐orbit coupling reveal that Cs2(Li/Na)GaI6 exhibits a direct bandgap, with values of 1.24 eV for Cs2LiGaI6 and 1.39 eV for Cs2NaGaI6. The exceptional optical properties, including a high absorption coefficient (105 cm−1) and excellent optical conductivity with low reflectivity across the entire UV–visible range, indicate that Cs2(Li/Na)GaI6 are promising materials for solar cell applications. Moreover, the ultralow thermal conductivity, high Seebeck coefficient, and substantial electrical conductivity of Cs2(Li/Na)GaI6 result in a high figure of merit over the temperature range of 200–600 K. Thus, Cs2(Li/Na)GaI6 shows strong potential as both photovoltaic and thermoelectric materials.

Effect of Molecular Conformation on Intermolecular Interactions and Photovoltaic Performances of Giant Molecule Acceptors

AbstractThe molecular conformation of giant molecule acceptors (GMAs) plays a significant role in regulating the intermolecular interactions and their photovoltaic performances in organic solar cells (OSCs). For the linear GMA GT‐l, the stronger homo‐molecular interaction causes its aggregation being weakly affected by the donor, thus forming an ordered molecular stacking and proper phase separation in its blend film. The star‐shaped GMA GT‐s‐based blend film shows a dominant hetero‐molecular interaction that suppresses the aggregation of the donor and acceptor, resulting in smaller phase separation and more uniform vertical phase distribution. While for another star‐shaped GMA GTs, the weakest hetero‐molecular interaction causes its blend film to form larger phase separation. Therefore, the GT‐l based OSC with PM6 as donor shows the highest charge mobilities, the fastest charge transfer (CT) process, reduced energy loss and less charge recombination, contributing to a higher power conversion efficiency (PCE) of 19.03%. Comparatively, the PCEs of the OSCs based on GTs and GT‐s are 18.05% and 17.58% respectively. Notably, all the three GMAs based OSCs show excellent thermal stability and long‐term storage stability. This study provides a facile strategy by tuning the linking unit and its connecting mode for designing highly efficient and stable organic photovoltaic materials.

Compact microstructured Cu2ZnSnS4 thin films with enhanced optoelectronic properties via (NH4)2S tunable hybrid colloidal ink coating and transformation

Kesterite Cu2ZnSnS4 (CZTS) is a quaternary semiconductor material composed of earth-abundant elements that is a promising material for sustainable thin film photovoltaics and other optoelectronic applications. In this work, CZTS thin films are deposited using aqueous colloidal suspensions of binary sulfides (Cu and Zn) and thiostannate complexes formed by in situ reaction of SnS2 with (NH4)2S. In a departure from previous works that used only dissolved thiostannate complexes, we utilize a hybrid state of tin sulfide as both nanoparticles and thiostannate complexes to improve thin film quality. This finding was made by adjusting the (NH4)2S concentration in our aqueous inks, which modified the relative abundance of thiostannate complexes vis-à-vis the amount of SnS2 nanoparticles. In the absence of (NH4)2S, the unstable ink yields nonuniform, partially oxidized thin films. Meanwhile, thiostannate complex formation with the use of (NH4)2S (2–10 vol%) can suppress the presence of secondary phases such as CuxS in the absorber layer and protects against oxidation (avoiding undesirable SnO2 formation). Lowering the aqueous (NH4)2S concentration to 2 vol% yielded the most stable ink formulation, featuring a hybrid state of tin sulfide as both colloidal particles and dissolved thiostannate complexes. The hybrid tin sulfide ink produced compact thin films and reduced the level of Cu-Zn antisite defects in the kesterite crystal structure. We attribute the compact microstructure attained with the hybrid tin sulfide formulation to thiostannate complexes acting as linkers among the three binary sulfides (Cu, Zn, and Sn), enabling their orderly packing into an amorphous, quaternary initial state which is then annealed to grow crystalline kesterite CZTS. UV-Vis absorption characterization shows the Tauc bandgap for 2 vol% hybrid ink coated films to be 1.40 eV with reduced absorption tails based on Urbach energy measurements, while photoluminescence studies showed significantly enhanced emission.

Enhancement of photovoltaic efficiency in BiVO4 films through Zr4+-W6+ Co-doped

Using a cost-effective and simple sol-gel process, BiVO4 films and Zr4+-W6+ co-doped BVO films were prepared on Pt/Ti/SiO2/Si substrates. The influence of Zr4+-W6+ co-doped on the photovoltaic properties of the synthesized BiVO4 films was systematically investigated. When the doped amount of Zr4+-W6+ is 6 %, the optical band gap of the film decreases from 2.58 eV to 2.31 eV. The increased strength of the built-in electric field of the films help to improve the separation of photogenerated charge carriers. The Zr4+-W6+ co-doped BiVO4 films demonstrated a significant increase in photocurrent density from 0.284 mA/cm2 to 1.04 mA/cm2. These findings highlight the potential of Zr4+-W6+ co-doped in advancing the performance of BiVO4-based photovoltaic materials and suggest avenues for future applications in solar energy devices.

An organic visible-photocatalytic-adsorbence mechanism to high-efficient removal of heavy metal antimony ions

Purification of emerging heavy metal antimony contaminated water based on advanced ingenious strategies. An activated modified coconut shell charcoal (CSC) was synthesized and evaluated as a substrate-supported loaded organic photovoltaic material, PM6:PYIT:PM6-b-PYIT, to prepare a surprisingly highly efficient, stable, environmentally friendly, and recyclable organic photocatalyst (CSC–N–P.P.P), which showed excellent effects on the simultaneous removal of Sb(III) and Sb(V). The removal efficiency of CSC-N-P.P.P on Sb(Ⅲ) and Sb(V) reached an amazing 99.9% in quite a short duration of 15 min. At the same time, under ppb level and indoor visible light (∼1 W m−2), it can be treated to meet the drinking water standards set by the European Union and the U.S. National Environmental Protection Agency in 5 min, and even after 25 cycles of recycling, the efficiency is still maintained at about 80%, in addition to the removal of As (III), Cd (II), Cr (VI), and Pb (II) can also be realized. The catalyst not only solves the problems of low reuse rate, difficult structure adjustment and high energy consumption of traditional photocatalysts but also has strong applicability and practical significance. The pioneering approach provides a much-needed solution strategy for removing highly toxic heavy metal antimony pollution from the environment.

Study on the Key Parameters Affecting the Power Conversion Efficiency of Cs2AgBiBr6-Based Perovskite Solar Cells

The lead-free halide double perovskite material A2BB’X6 represented by Cs2AgBiBr6, has higher potential as a photovoltaic material since it has good electronic and optical properties in recent years. However, the highest power conversion efficiency (PCE) achieved for solar cells made with Cs2AgBiBr6 as the light-absorbing layer in experiments is only 2.51%. To investigate this phenomenon, we used the Solar Cell Capacitance Simulator (SCAPS) simulation software to build five solar cell models with the structure of FTO/ZnO/Light-absorbing layer/Cu2O/Au based on different light-absorption layer materials. Two reasons causing the low PCE of Cs2AgBiBr6 solar cells were identified. On the one hand, interlayer defects in Cs2AgBiBr6 film synthesis significantly decreased the fill factor (FF), thereby reducing the quantum efficiency (QE). On the other hand, Cs2AgBiBr6’s larger indirect bandgap resulted in a narrower absorption range. Additionally, it was demonstrated that adjusting the material thickness and alloying method could, respectively, improve the two aforementioned issues. When the thickness of the light-absorbing layer material was 300[Formula: see text]nm, the FF increased from 39.88% to 55.01%, resulting in an optimal PCE of 3.88% for the solar cell. Alloying increased the short-circuit current ([Formula: see text]) from 8.44[Formula: see text]mA/cm2 to 21.24[Formula: see text]mA/cm2, leading to a simulated PCE increase of 8.92% for solar cells based on Cs2NaSb[Formula: see text]In[Formula: see text]I6. This work, from the perspective of device simulation, is highly significant for improving the photoelectric conversion efficiency of Cs2AgBiBr6-based perovskite solar cells in experimental settings. It offers new insights for optimizing solar cell efficiency.

The electronic stopping power of self-irradiated molybdenum in different charge states

Molybdenum is not only an excellent photovoltaic material but also a crucial component in semiconductors. However, its high bandgap restricts its application in optoelectronic devices. This limitation arises primarily because the energy barrier between photogenerated electron-hole pairs cannot be directly overcome by sunlight. Self-irradiation can overcome these barriers, allowing efficient separation of photogenerated electrons and holes, making molybdenum an excellent light-absorbing material. By altering the charge state of molybdenum-based materials, their light absorption can be adjusted. This project aims to systematically study the optical properties and electronic stopping power of molybdenum-based materials in different charge states through theoretical calculations and experiments.

Effect of different contact interfaces on electronic and optical properties in the heterojunction of SiC2/MoSSe

We investigate the effect of different contact interfaces on the electronic and optical characteristics of the SiC2/MoSSe heterojunction. It is found that SiC2/MoSSe(S) heterojunction is an indirect band gap semiconductor with type II band alignment. The SiC2/MoSSe (Se) heterojunction is a direct band gap semiconductor with a type Ⅰ band alignment. The difference in electronic properties between the two heterostructures comes from the different orientations of the intrinsic electric field of Janus MoSSe in the heterojunction. The band gap and energy band alignment are modulated under the applied electric field. Moreover, the optical properties of SiC2/MoSSe (Se) are better than the SiC2/MoSSe(S), and the applied electric field can improve the optical properties of the heterojunction. The results provide a potential way for efficient photovoltaic materials.

Excitonic Properties versus Structure Stability Trade‐Off in Halide Perovskite Photovoltaics Caused by van der Waals Interactions

Lead halide perovskites, and their derivatives, are among the most promising photovoltaic materials for third generation solar cells. Despite the large number of available works on some of these materials, excitonic properties whose assessment has been challenging are less investigated. These include quantitative measures of excitonic properties variations with van der Waals (vdW) interactions. Consistent comparisons of how vdW interactions affect phononic and optical properties are also desirable. This work focuses on cubic phases of with X = Cl, Br, I, and MA = methylammonium, using density functional theory simulations including vdW interactions. These cause 30%–38% increase of absolute cohesive energies and 15%–37% reduction of ionic/vibrational contributions to static dielectric constants, along with 10%–29% reduction of exciton Bohr radii and 29%–107% increase of exciton binding energies. The effects on band gaps, frequency‐dependent dielectric functions, and exciton effective masses are less pronounced. Within the Mott–Wannier exciton model, the results suggest a trade‐off between photovoltaic performance and structure stability. The results can help assess stability, feasibility, and performance of hybrid photovoltaic materials.

“Green” Aqueous Synthesis, Structural, and Optical Properties of Quaternary Cu2ZnSnS4 and Cu2NiSnS4 Nanocrystals

Element substitution in Cu2ZnSnS4‐like chalcogenides offers the potential to create alternative low‐cost photovoltaic and thermoelectric materials with tunable properties. In this work, the “green” synthesis of colloidal cation‐substituted Cu–Ni–Sn–S nanocrystals (CNTS NCs) in aqueous solutions using thioglycolic acid as a stabilizer is reported for the first time. The structural and optical properties of CNTS NCs are studied in colloidal solutions and thin films, and are compared with those of Cu–Zn–Sn–S (CZTS) NCs obtained under similar conditions. The NC sizes of both compounds are estimated to be in the range of 1.5–2.5 nm. Both NCs exhibit strongly non‐stoichiometric composition and a structure corresponding to cationically disordered kesterite Cu2ZnSnS4, which are common features of such quaternary metal‐based chalcogenides. The phonon Raman spectra of CNTS and CZTS NCs exhibit very similar lineshapes, but the CNTS phonon band has a larger width and lower frequency, presumably due to stronger cation disorder. The absorption of both types of NCs extends continuously through the visible range with an estimated bandgap of ≈2.2 eV and sub‐bandgap absorption due to an Urbach tail. The absorption coefficient of CNTS is determined to be α > 102 cm−1 at 700 nm and α > 104 cm−1 at 400 nm.

A High-Performance Organic Photovoltaic System with Versatile Solution Processability.

Recently developed organic photovoltaic (OPV) materials have simultaneously closed the gaps in efficiency, stability, and cost for single-junction devices. Nonetheless, the developed OPV materials still pose big challenges in meeting the requirements for practical applications, especially regarding the prevalent issues of solution processability. Herein, a highly efficient polymer donor, named DP3, incorporating an electron-rich benzo[1,2-b:4,5-b']dithiophene unit as well as two similar and simple acceptor units is presented. Its primary objective is to enhance the interchain and/or intrachain interactions and ultimately fine-tune bulk-heterojunction microstructure. The DP3:L8-BO system demonstrates the highest power conversion efficiency (PCE) of 19.12%. This system also exhibits high-performance devices with over 18% efficiencies for five batches with various molecular weights (23.6-80.8KDa), six different blend thicknesses (95-308nm), differenced coating speeds (3.0-29.1mmin-1), with promising PCEs of 18.65% and 15.53% for toluene-processed small-area (0.029cm2) cells and large-area (15.40cm2) modules, thereby demonstrating versatile solution processability of the designed DP3:L8-BO system that is a strong candidate for commercial applications.

Synergistic charge-transfer dynamics of rigid fused and unfused backbone with donors lead to promising photovoltaic properties of diazaborinine-based chromophores

Herein, a series of diazaborinin based derivatives (FABD1–FABD8) having D-π-D configuration was designed by inserting different types of rigid fused and unfused π-bridges into reference molecule (FABR) to explore their photovoltaic characteristics. To determine the optoelectronic and charge transport characteristics of these analogues, DFT/TD-DFT based calculations were conducted at the MPW1PW91/6-31G (d,p) level. For this, various analyses were performed such as transition density matrix (TDM), global reactivity parameters (GRP), open-circuit voltage (Voc), optical properties (UV–Vis), binding energy (Eb), hole-electron and frontier molecular orbital (FMO) energies. Their insights indicate that a rigid fused π-bridge greatly lowers the band gap as compared to an unfused π-spacers. Particularly, FABD7 showed the lowest energy gap of 2.20 eV owing to the presence of a rigid fused central core as compared to FABR with a band gap of 2.65 eV. Similarly, the entitled designed derivatives demonstrated a redshift absorption in the range of 585.7–704.6 nm while FABR is reported with 558.7 nm in the solvent phase. Furthermore, these derivatives displayed significant Voc with blending of PC61BM acceptor. This observation was also supported by DOS and TDM based insights. Interestingly, FABD7 seemed as a viable photovoltaic material due to its strong optical properties and small band gaps. These results uncover that the designed chromophores may be considered as efficient to enhance the performance of OSCs.

Spray-Coated Transition Metal Dichalcogenides as Hole Transport Layers in Inverted NFA-Based Organic Photovoltaics with Enhanced Stability under Solar and Artificial Light

In this study, we explored the potential of exfoliated transition metal dichalcogenides (TMDs) as innovative spray-coated hole transport layers (HTLs) in organic photovoltaics (OPVs), addressing the need for efficient and stable materials in solar cell technology. This research was motivated by the need for alternative HTLs that can offer enhanced performance under varying lighting conditions, particularly in indoor environments. Employing UV-visible absorption and Raman spectroscopy, we characterized the optical properties of MoS2, MoSe2, WS2, and WSe2, confirming their distinct excitonic transitions and direct bandgap features. The nanocrystalline nature of these TMDs, revealed through XRD patterns and crystallite size estimation using the Scherrer method, significantly contributes to their enhanced physical properties and operational efficiency as HTLs in OPVs. These TMDs were then integrated into OPV devices and evaluated under standard solar and indoor lighting conditions, to assess their effectiveness as HTLs. The results demonstrated that MoS2, in particular, displayed remarkable performance, rivalling traditional HTL materials like MoO3. It maintained high power conversion efficiency across a spectrum of light intensities, illustrating its versatility for both outdoor and indoor applications. Additionally, MoS2 showed superior stability over extended periods, suggesting its potential for long-term usage in OPVs. This study contributes significantly to the field of photovoltaic materials, presenting TMDs, especially MoS2, as promising candidates for efficient and stable OPVs in diverse lighting conditions, thereby broadening the scope of solar cell applications.