High Fill Factor Research Articles

Unveiling the mechanism of attaining high fill factor in silicon solar cells

AbstractA world record conversion efficiency of 26.81% has been achieved recently by LONGi team on a solar cell with industry‐grade silicon wafer (274 cm2, M6 size). An unparalleled high fill factor (FF) of up to 86.59% has also been certified in a separated device. The theoretical FF limit has been predicted to be 89.26%, while the practical FF is far below this limit for a prolonged interval due to the constraints of recombination (i.e., SRH recombination) and series resistance. The ideality factor (m) in the equivalent circuit of silicon solar cells is consistently ranging from 1 to 2 and rarely falls below 1, resulting in a relatively lower FF than 85%. Here, this work complements a systematic simulation study to demonstrate how to approach the FF limit in design of silicon solar cells. Firstly, a diode component with an ideality factor equal to 2/3 corresponding to Auger recombination is incorporated in the equivalent circuit for LONGi ultra‐high FF solar cell; Secondly, an advanced equivalent circuit is put forward for comprehensive analysis of bulk recombination and surface recombination on the performance, in which specific ideality factors are directly correlated with various recombination mechanisms exhibiting explicit reverse saturation current density (J0). Finally, we evaluate precisely the route for approaching theoretical FF in practical solar cell fabrication based on electrical design parameters using the developed model.

Permanent-magnet-based transverse thermoelectric generator with high fill factor driven by anomalous Nernst effect

A transverse thermoelectric generator for magnetic-field-free and high-density power generation utilizing the anomalous Nernst effect is constructed and its performance is characterized. By alternately stacking two different permanent magnets with the large coercivity and anomalous Nernst coefficients of opposite sign, transverse thermoelectric voltage and power can be generated in the absence of external magnetic fields and enhanced owing to a thermopile structure without useless electrode layers. In the permanent-magnet-based stack, the magnetic attractive force enables easy construction of the thermopile structure with a high fill factor. In this study, we construct a bulk module consisting of 12 pairs of SmCo5- and Nd2Fe14B-type permanent magnets having positive and negative anomalous Nernst coefficients, respectively, whose fill factor reaches ∼80%, whereas that of conventional thermoelectric modules based on the Seebeck effect is typically 30%–60%. We demonstrate magnetic-field-free anomalous Nernst power generation up to 177 µW at a temperature difference of 75 K around room temperature, which corresponds to the largest anomalous Nernst power density of 65 µW/cm2. The presented module structure concept will provide a design guideline for high-performance transverse thermoelectric power generation.

Fabrication of efficient natural dye-sensitized Solar Cells using Mediterranean olive leaves as natural dye sensitizer

The synthesis of synthetic dyes employed in dye-sensitized solar cells (DSSCs) is often associated with substantial costs and environmental concerns. As a result, there is growing interest in utilizing natural dyes as sensitizers for DSSCs. This paper presents a comprehensive investigation into the extraction of natural dyes from Mediterranean olive leaves using a methanol-based solution, with a particular focus on the impact of different drying times during the dye extraction process on the efficiency of fabricated solar cells. The extracted olive leaf dyes were systematically characterized, encompassing their optical properties analyzed through ultraviolet–visible (UV–Vis) and Fourier Transform Infrared (FTIR) spectroscopy, electrochemical behavior, photovoltaic performance, crystallographic and morphological structures, as well as elemental composition. The research findings unveiled distinctive attributes of the olive leaf dyes, attributable to variations in their charge transfer processes to the band edge of the TiO2 semiconductor. These outcomes were substantiated through comprehensive analyses involving UV–Vis, FTIR, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Notably, the olive leaf dye subjected to a longer drying time (referred to as OLDS1) exhibited an energy level of the lowest unoccupied molecular orbital (LUMO) closer to that of the conduction band of TiO2, facilitating efficient electron transfer. Furthermore, X-ray photoelectron spectroscopy revealed alterations in elemental composition upon dye adsorption onto the TiO2 surface, with a notable reduction in the intensities of the Ti 2p and O 1 s peaks. The OLDS1 dye demonstrated lower charge transfer resistance and recombination rates compared to the shorter drying time for both fluorine-doped tin oxide (FTO) and indium-doped tin oxide (ITO)-based natural DSSCs (NDSSCs). Importantly, the choice of substrate material, specifically FTO and ITO, significantly influenced the NDSSC performance. The FTO/TiO2/OLDS1 configuration exhibited remarkable characteristics, including a high fill factor (FF) of approximately 0.73 and an efficiency of 0.31 %, accompanied by a short-circuit current density of 0.662 mA/cm2 and an open-circuit voltage of 0.642 V. These results highlight the crucial role of drying time and substrate selection in the fabrication of NDSSCs utilizing Mediterranean olive leaf extracts, with the FTO/TiO2/OLDS1 configuration emerging as the most promising and efficient combination.

The Influence of Donor/Acceptor Interfaces on Organic Solar Cells Efficiency and Stability Revealed through Theoretical Calculations and Morphology Characterizations

AbstractEnd‐groups halogenation strategies, generally refers to fluorination and chlorination, have been confirmed as simple and efficient methods to regulate the photoelectric performance of non‐fullerene acceptors (NFAs), but a controversy over which one is better has existed for a long time. Here, two novel NFAs, C9N3‐4F and C9N3‐4Cl, featured with different end‐groups were successfully synthesized and blended with two renowned donors, D18 and PM6, featured with different electron‐withdrawing units. Detailed theoretical calculations and morphology characterizations of the interface structures indicate NFAs based on different end‐groups possess different binding energy and miscibility with donors, which shows an obvious influence on phase‐separation morphology, charge transport behavior and device performance. After verified by other three pairs of reported NFAs, a universal conclusion obtained as the devices based on D18 with fluorination‐end‐groups‐based NFAs and PM6 with chlorination‐end‐groups‐based NFAs generally show excellent efficiencies, high fill factors and stability. Finally, the devices based on D18: C9N3‐4F and PM6: C9N3‐4Cl yield outstanding efficiency of 18.53 % and 18.00 %, respectively. Suitably selecting donor and regulating donor/acceptor interface can accurately present the photoelectric conversion ability of a novel NFAs, which points out the way for further molecular design and selection for high‐performance and stable organic solar cells.

The Influence of Donor/Acceptor Interfaces on Organic Solar Cells Efficiency and Stability Revealed through Theoretical Calculations and Morphology Characterizations.

End-groups halogenation strategies, generally refers to fluorination and chlorination, have been confirmed as simple and efficient methods to regulate the photoelectric performance of non-fullerene acceptors (NFAs), but a controversy over which one is better has existed for a long time. Here, two novel NFAs, C9N3-4F and C9N3-4Cl, featured with different end-groups were successfully synthesized and blended with two renowned donors, D18 and PM6, featured with different electron-withdrawing units. Detailed theoretical calculations and morphology characterizations of the interface structures indicate NFAs based on different end-groups possess different binding energy and miscibility with donors, which shows an obvious influence on phase-separation morphology, charge transport behavior and device performance. After verified by other three pairs of reported NFAs, a universal conclusion obtained as the devices based on D18 with fluorination-end-groups-based NFAs and PM6 with chlorination-end-groups-based NFAs generally show excellent efficiencies, high fill factors and stability. Finally, the devices based on D18: C9N3-4F and PM6: C9N3-4Cl yield outstanding efficiency of 18.53 % and 18.00 %, respectively. Suitably selecting donor and regulating donor/acceptor interface can accurately present the photoelectric conversion ability of a novel NFAs, which points out the way for further molecular design and selection for high-performance and stable organic solar cells.

Effect of Silver Powder Microstructure on the Performance of Silver Powder and Front-Side Solar Silver Paste.

Silver powder, as the primary component of solar silver paste, significantly influences various aspects of the paste's performance, including printing, sintering, and conductivity. This study reveals that, beyond the shape and size of the silver powders, their microstructure is a critical factor influencing the performance of both silver powders and silver pastes in solar cell applications. The growth process leads to the formation of either polycrystalline aggregated silver powder or crystal growth silver powder. Analyzing the performance characteristics of these different microstructures provides guidance for selecting silver powders for silver pastes at different sintering temperatures. Polycrystalline aggregated silver powder exhibits higher sintering activity, with a sintering initiation temperature around 450 °C. The resulting silver paste, sintered at 750 °C, demonstrates a low sheet resistance of 2.92 mΩ/sq and high adhesion of 2.13 N. This silver powder is suitable for formulating silver pastes with lower sintering temperatures. The solar cell electrode grid lines have a high aspect ratio of 0.37, showing poor uniformity. However, due to the high sintering activity of the silver powder, the glass layer dissolves and deposits more silver, resulting in excellent conductivity, a low contact resistance of the silver electrode, a low series resistance of the solar cell of 1.23 mΩ, and a high photoelectric conversion efficiency of 23.16%. Crystal growth silver powder exhibits the highest tap density of 5.52 g/cm3. The corresponding silver paste shows improved densification upon sintering, especially at 840 °C, yielding a sheet resistance of 2.56 mΩ/sq and adhesion of 3.05 N. This silver powder is suitable for formulating silver pastes with higher sintering temperatures. The solar cell electrode grid lines are uniform with the highest aspect ratio of 0.40, resulting in a smaller shading area, a high fill factor of 81.59%, and a slightly higher photoelectric conversion efficiency of 23.17% compared to the polycrystalline aggregated silver powder.

Comparative study on perovskite solar cells using P_ZnO, Al_ZnO and In_ZnO as ETMs by SCAPS-1D

This study uses the SCAPS 1D software to analyze solar cells with lead iodide perovskite (CH3NH3PbI3) as the active material and three different types of ZnO doping: undoped (P_ZnO), aluminum-doped (Al_ZnO), and indium-doped (In_ZnO) as the electron transport layer (ETL). This study aims to investigate the effects of charge carrier density on the J-V characteristics and electrical properties (Jsc, Voc, FF, Eff) of a solar cell structure made up of FTO/ETL/CH3NH3PbI3/CuInSe2/Au. Gold makes up the back contact, and tin oxide doped with fluorine (FTO) makes up the front contact. These two compounds have work roles are 5.47 eV and 4.4 eV respectively. Zinc oxide, both undoped and doped, makes up the electron transport layer, whereas methyl ammonium lead iodide makes up the absorber layer. Thin sheets, indium diselenide, and copper make up the hole transport layer. An optimal perovskite layer was obtained by decreasing the electron transportation layer's thickness (ETL) from 500 to 100 nm. For the In_ZnO ETL, this optimization was accomplished at 300K working temperature. Reduced ETL thickness was shown to result in higher efficiency (above 27%), as well as higher fill factor (above 87%). With a Voc value of 1.180V, a FF value of 87.55%, and a Jsc value of 26.276mA/cm2, the greatest efficiency performance of 27.15% was found. Using an absorber layer made of CH3NH3PbI3 with a thickness of 800 nm and indium-doped oxide of zinc (In_ZnO) is the layer that transports electrons, this performance was achieved. The results are obtained at a constant irradiance level of 1000 W/m2, under the AM1.5G spectrum.

Carboxymethyldextran sodium-modified SnO2 enables highly efficient and stable perovskite solar cells with a high fill factor of 84.89%

Carboxymethyldextran sodium (CMD) was used to modify tin dioxide to prepare highly efficient and stable SnO2-based perovskite solar cells, in which the filling factor was as high as 84.89%.

Conductor Design Method considering AC Resistance for High Efficiency of PMSM using High Fill Factor Winding

Conductor Design Method considering AC Resistance for High Efficiency of PMSM using High Fill Factor Winding

Molecular engineering of BTO for superior photovoltaic efficiency: A DFT exploration

In this study, Density Functional Theory (DFT) was employed using Gaussian 09 software to optimize the molecular structures of reference and designed molecules. Various functionals (PBE0, B3PW91, TPSSh, CAM-B3LYP, MPW1P91, ωB97XD, and B3LYP) and basis sets (6-31G(d,p), 6-311-G(d,p), and def2-tzvp) were utilized to determine the optimal computational parameters. The computed results showed that the synthesized molecules with electron-donor groups exhibited decreased binding energies, indicating improved charge transfer. Dipole moments were calculated, revealing that the designed molecules had enhanced solubility in chlorobenzene solvent. These modifications also led to improved charge transmission and exciton dissociation, making the molecules potential candidates for organic solar cells. The designed compounds displayed altered voltage of open circuit (VOC) values and higher fill factor (FF) values compared to the reference molecule. The fill factor values indicated enhanced performance in charge collection and extraction efficiency. The power conversion efficiency (PCE) values of the designed molecules exceeded that of the reference molecule, with BTO-A5 (43.61 %) exhibiting the highest PCE value. Overall, the study demonstrated the potential of the designed molecules for high-performance solar devices. Further research could explore their application in solar energy conversion technologies.

(Invited) Chirality-Induced Spin Selectivity Enabling Efficient Spin-Dependent Oxygen Evolution Reaction and High-Performance Photoelectrochemical Water Splitting

The sluggish and complex multi-step oxygen evolution reaction (OER) remains an obstacle to bias-free photoelectrochemical water-splitting systems. Several theoretical and experimental studies have suggested that OER efficiency can be significantly enhanced in chiral material-based photoanodes by utilizing the chirality-induced spin selectivity (CISS) phenomenon. The final product at the photoanode is the oxygen molecules, where the spin alignment of intermediate radicals is favorable to the generation of triplet 3O2 (most stable molecular oxygen species). Considering the energy difference between a singlet 1O2 and triplet 3O2, spin-dependent chemical reactions combined with the CISS phenomenon can play a crucial role in the OER process. Moreover, chiral material-based photoanodes are capable of paralleling spin distribution on the catalytic surface. The resulting spin-aligned intermediate radicals can promote the generation of spin-allowed triplet 3O2 over that of singlet oxygen, while hindering the formation of hydrogen peroxide, in turn leading to the enhanced STH efficiency of the overall PEC water-splitting system. In this regard, chiral materials (as a spin-filter layer) have been recognized as promising candidates for achieving a breakthrough in the solar-to-hydrogen efficiency of water-splitting devices. Herein, we report that the CISS phenomena can become an impressive approach by adopting chiral 2D organic-inorganic hybrid perovskites (OIHPs) as a spin-filtering layer on the 3D OIHP photoanode. Our chiral 2D OIHP-based water-splitting device achieved enhanced oxygen evolution performance with a reduced overpotential of 0.2 V, high fill factor, and increased photocurrent of 22 mA cm–2 at 1.2 VRHE compared to a device without a spin-filtering layer. For unbiased water splitting, a perovskite-based photocathode decorated with a spatially decoupled hydrogen evolution reaction catalyst is fabricated. This decoupled geometry enables the physical protection of the perovskite layer from the electrolyte, thus allowing excellent stability for over 100 h. To investigate the overall water splitting performance, this perovskite photocathode is connected in parallel with spin-filtering layer adopted photoanode based on chirality-induced spin selectivity. An unbiased solar water splitting was achieved using all the OIHP photoelectrodes, resulting in a remarkable unassisted solar-to-hydrogen efficiency of ~12% and a continuous 10 h stable operation.

Intermediate Phase Modification Enables High‐Performance Iodine‐Rich Inorganic Perovskite Solar Cells with 3000‐Hour Stability

AbstractThe presence of excess secondary‐phase PbI2 in perovskite films shows a negative impact on their long‐term stability. Herein, an intermediate phase modification (IPM) strategy is proposed to eliminate residual PbI2 for improved quality of all‐inorganic CsPbI3‐type perovskite films, wherein the extrinsic agent is introduced to address the intermediate phase. By transforming residual PbI2 into a novel 1D perovskite phase, the IPM strategy acts as a patch to suture grain boundaries in the inorganic perovskite films. In addition, the IPM strategy not only enhances the quality of perovskite films but also mitigates energy disorder, reduces trap state density, and prolongs carrier lifetime by expediting the intermediate phase conversion process and passivating surface defects. As such, the perovskite solar cells (PSCs) with a high power conversion efficiency (PCE) of ≈20% and a high fill factor of 83.3% are considered to be very efficient, with excellent shelf stability of 3000 h of exposure in air without any encapsulation. This work not only exhibits a novel optimization route for inorganic perovskite but also emphasizes the crucial role of eliminating residual PbI2 in inorganic perovskites.

Over 35% efficiency of three absorber layers of perovskite solar cells using SCAPS 1-D

Perovskite solar cells (PSCs) have drawn significant scientific interest due to their promising combination of high power conversion efficiency and cost-effectiveness. This study focuses on optimizing the power conversion efficiency (PCE) of PSCs by employing absorber layers comprising CH3NH3SnI3 and FASnI3. The Solar Cell Capacitance Simulator (SCAPS) is used to investigate various parameters, including layer thickness, defect densities (Nt), bandgap values, and temperature. The most efficient configuration is found with 390 nm layer thickness, Nt at 2E13 cm3, and optimized bandgap values. The study reveals impressive electrical parameters, including an open-circuit voltage (Voc) of 1.23 V, short-circuit current density (Jsc) of 33.43 mA/cm2, a high fill factor (FF) at 88.64%, and a substantial PCE of 35.73%. These findings underscore the potential for achieving superior PSC efficiency through parameter optimization. The utilization of CH3NH3SnI3 and FASnI3 absorber layers holds great promise for enhancing PSC performance. This research provides valuable insights into optimizing PSCs, offering implications for the advancement of cost-effective and efficient photovoltaic technologies.

Optimal design of optomechanical uncooled infrared focal plane array with integrated metalens

Optomechanical uncooled infrared (IR) detectors based on the thermal deformation of bi-material micro-cantilever have proved of significant potential in the IR imaging fields. However, compared to other uncooled infrared detectors, the optomechanical type relies on the mechanical deformation of the thermomechanical cantilevers, which compete for space with the absorbers and isolation beams, resulting in limited sensitivity. By integrating a designed metalens, large deformation, high thermal isolation, and high effective fill factor can be achieved simultaneously. Several pixel designs of optomechanical uncooled IR focal plane array (FPA) with designed integrated metalens are evaluated and optimized through numerical simulation. High thermal conversion efficiency and thermomechanical sensitivity μm K−1 are simultaneously achieved with an inherent noise-equivalent temperature difference(NETD) value of mK at the preset × pixels. Using Figure of Merit(FOM) as a comprehensive evaluation of NETD and response time, the optimized structure can be improved by up to 40% over the original structure.

Tailored Succinic Acid-Derived Molecular Structures toward 25.41%-Efficiency and Stable Perovskite Solar Cells.

Minimizing interfacial charged traps in perovskite films is crucial for reducing the non-radiative recombination and improving device performance. In this study, succinic acid (SA) derivatives varying active sites and spatial configurations are designed to modulate defects and crystallization in perovskite film. The SA derivative with two symmetric Br atoms, dibromosuccinic acid (DBSA), exhibits the optimal spatial arrangement for defect passivation. Experimental and theoretical results indicate that the carboxyl group and atomic Br in DBSA synergistically interact with the under-coordinated Pb2+ . Moreover, the strong electronegativity of Br efficiently stabilizes the formamidinium cation via electrostatic interaction. Consequently, film quality is significantly improved and non-radiative recombination is markedly depressed, resulting in a photoluminesence lifetime of exceeding 4µs of and a carrier diffusion length of 3µm. An exceptional efficiency of 25.41% (certified at 25.00%) along with a high fill factor of 84.39% and excellent long-term operational stability have been achieved finally.

Insights into efficiency deviation from current-mismatch for tandem photovoltaics

For tandem solar cells (TSCs), the highest efficiency is generally believed to occur when the top and bottom sub-cells obtain an identical photocurrent, i.e., the current-match condition. However, the real situation is that there is a slight deviation from the matching point, which is an interesting phenomenon, but lacks a clear explanation. Here, we report a coupled photoelectric investigation on the intrinsic mechanisms within TSCs under various current configurations. Taking an all-perovskite TSC as an example, we find that the efficiency deviation originates from the current reduction and fill factor (FF) compensation; moreover, the optimal efficiency depends primarily on the sub-cells with higher FF. Our analysis further reveals that the higher FF and efficiency are achieved under current-mismatch condition due to the differentiated voltage assignments among the sub-cells, i.e., the sub-cells with higher currents require larger voltages in order to effectively recombine the surplus currents. We also find that the impact of sub-cell leakage on TSC performance can be partially alleviated by increasing the current of the affected sub-cell. Such an optoelectronic insight offers a valuable guidance for designing high-efficiency TSCs.

Enhancing the Efficiency of PM6:Y6 Bulk-Heterojunction Organic Solar Cells through SCAPS Simulation Optimization

Organic solar cell (OSC) is becoming a point of attraction in the solar cell industry due to their benefits, such as light weight, flexibility, low cost, semi-transparency, and easy fabricating methods. By replacing fullerene with non-fullerene acceptors like Y6, ITIC, PCBM, and ICBA, the power conversion efficiency (PCE) of OSCs has surpassed the 15% benchmark. Here, the proposed OSC structure includes an ITO front contact electrode, SnO2 electron transport layer (ETL), PM6:Y6 active layer, Cu2O hole transport layer (HTL), and Ag back contact electrode. Systematic numerical simulation of the above proposed OSC has been performed using a solar cell capacitance simulator (SCAPS)-1D (Version 3.3.09). The device improvement analysis has been carried out in steps by analyzing the ETL-HTL effect, selecting the optimum thickness of the active layer, and the optimum value of defect density. In the first step, a PCE of 24.60% was achieved, followed by an improvement to 27.55% with the optimized defect density value. The best PCE of 27.74% was achieved in the third step with an optimized active layer thickness, leading to high fill factor (80.56%), open-circuit voltage (0.9461 V), and short-circuit current density (36.188 mA/cm2). These simulated results promote an in-depth understanding of the optical and electronic properties of PM6:Y6 blend-based OSC and show the potential of NFA-BHJ OSCs as promising candidates for solar cells in the near future.

Predicting and analyzing the fill factor of non-fullerene organic solar cells based on material properties and interpretable machine-learning strategies

In recent years, encouraging progress in non-fullerene acceptors-based organic solar cells (NFAs-OSCs) has been made in the field of clean-energy technologies. Nevertheless, achieving a high fill factor (FF) for NFAs-OSCs is a great challenge due to the FF value can be dramatically affected by various factors. An accurate prediction (based on empirical data) of how inherent characteristics of polymer-NFA combinations (e.g., frontier molecular orbitals (FMO) and charge-carrier mobilities) affects the FF in NFAs-OSCs is therefore urgently needed for the future commercialization prospect. The presented work demonstrates an outperforming predictive model using the optimized Gradient-boosting decision tree (GBDT) machine learning (ML) algorithm to accurately predict the FF value, which is based on a dataset consisting of > 180 unique donor/NFA blends with reported FF from previously published publications and experimental physical descriptors (FMO and charge-carrier mobilities). In addition, the SHapley Additive exPlanations (SHAP) strategy is further applied to not only gain the interpretability of the GBDT model prediction but also directly map the relationship between the FF value and experimental physical descriptors by systematic interpretable explanations (e.g., global and local). The SHAP analysis qualitatively reveals that the highest occupied molecular orbital (HOMO) of the donor and the HOMO of the acceptor are the two most important features associated with FF value prediction, which is in good agreement with previous experimental facts. Furthermore, the ML strategies explore the key requirements (e.g., small HOMO offset (<0.3 eV), high hole and electron mobilities (>1.0 × 10–4 cm2 V−1 s−1), and desired μh/μe ratio (in the range of 1.8–3.3)) for enhancing the FF values of NFAs-OSCs. This study provides novel insights into the possible physical mechanisms of FF enhancement, thus facilitating research efforts (e.g., rational design of energy level tuning in donor/NFA blend) for high-performance NFAs-OSCs.

Development of Shape Prediction Model of Microlens Fabricated via Diffuser-Assisted Photolithography.

The fabrication of microlens arrays (MLAs) using diffuser-assisted photolithography (DPL) has garnered substantial recent interest owing to the exceptional capabilities of DPL in adjusting the size and shape, achieving high fill factors, enhancing productivity, and ensuring excellent reproducibility. The inherent unpredictability of light interactions within the diffuser poses challenges in accurately forecasting the final shape and dimensions of microlenses in the DPL process. Herein, we introduce a comprehensive theoretical model to forecast microlens shapes in response to varying exposure doses within a DPL framework. We establish a robust MLA fabrication method aligned with conventional DPL techniques to enable precise shape modulation. By calibrating the exposure doses meticulously, we generate diverse MLA configurations, each with a distinct shape and size. Subsequently, by utilizing the experimentally acquired data encompassing parameters such as height, radius of curvature, and angles, we develop highly precise theoretical prediction models, achieving R-squared values exceeding 95%. The subsequent validation of our model encompasses the accurate prediction of microlens shapes under specific exposure doses. The verification results exhibit average error rates of approximately 2.328%, 7.45%, and 3.16% for the height, radius of curvature, and contact angle models, respectively, all of which were well below the 10% threshold.

Incorporation of Liquid Metal Gallium into Carbon Electrode for Efficient Charge Transportation in Planar Perovskite Solar Cells

Carbon electrode‐based perovskite solar cells (C‐PSCs) exhibit a promising future for commercialization, due to their low cost, facile fabrication, and mass production potential. However, compared with metal‐based counter electrodes, carbon electrodes (CEs) often suffer from relatively low electrical conductivity, porous and rough morphology leading to poor interfacial contact with the underneath layer thereby restricting the power conversion efficiency (PCE) of C‐PSCs. Herein, a simple approach is presented to prepare liquid metal/carbon composite electrodes by uniformly dispersing liquid gallium droplets into CEs to enhance both the electrical conductivity and interfacial contact between carbon and the adjacent layer. Compared to control devices without Ga, the Ga‐embedded carbon also creates a more favorable energy band alignment with the hole transport layer underneath for efficient hole transport, thus suppressing recombination at the interfaces. By optimizing the weight ratio between Ga and the carbon paste, the corresponding C‐PSCs deliver an optimum PCE of 13.99% with a higher fill factor (68.95%) compared to pristine C‐PSCs (PCE = 13.13%). In addition, the Ga‐containing devices demonstrate reinforced thermal stability with 65% efficiency retention after 1800 min under a thermal stress of 80 °C without encapsulation.