Top Cell Research Articles

CsF Improved Buried Interface for Efficient and Stable Inverted All-inorganic CsPbI2.85Br0.15 Perovskite Solar Cells

All-inorganic CsPbIxBr3-x is frequently used as the top cells in tandem devices due to its tunable bandgap, making it highly promising for future development. However, CsPbIxBr3-x films typically contain numerous defects at the interfaces and grain boundaries, significantly hindering carrier transport and thus reducing the device performance. Interface modification is commonly employed to passivate defects and enhance carrier transport at the interfaces. In this work, CsF was used to modify the buried interface between the perovskite film and self-assembled monolayers (SAMs). The interaction between fluoride ions (F⁻) and uncoordinated Pb2⁺ contributed to reduce defect density, enhance crystallization quality, and suppress non-radiative carrier recombination at buried interface. Consequently, the efficiency of inverted CsPbI2.85Br0.25 PSCs with CsF improved from 16.15% to 18.24%, compared to the control device. Moreover, the unencapsulated CsF-modified device retained 89% of its initial efficiency after storing for 600 h in ambient air with room-temperature and relative humidity (RH) of 20%. This demonstrates that CsF modification significantly enhances both the performance and stability of CsPbI2.85Br0.15 perovskite solar cells.

Simulating High‐Efficiency, Lead‐Free Inorganic‐Organic Perovskite Tandem Solar Cells with over 46% Efficiency

AbstractPerovskite‐based tandem solar cells (SCs) show significant potential for improving efficiency. In this study, three configurations were designed and optimized: a top cell (ITO/ZnSe/CH3NH3GeI3/CuSCN/Ni), a bottom cell (ITO/ZnSe/CH3NH3SnI3/CuI/Ni), and a tandem cell combining both. Using SCAPS‐1D, the study evaluated how the absorber layer thickness, doping concentration, and defect density affected photovoltaic (PV) performance. It also explored the influence of doping in the back surface field (BSF), interface defect densities, temperature, and back contact work function. The top cell achieved a power conversion efficiency (PCE) of 28.47%, with an open‐circuit voltage (VOC) of 1.21 V, a short‐circuit current density (JSC) of 27.17 mA/cm2, and a fill factor (FF) of 86.24%. The bottom cell reached a PCE of 18.46%, with a VOC of 0.83 V, a JSC of 27.17 mA/cm2, and an FF of 81.839%. The optimized tandem structure demonstrated a notably higher efficiency of 46.89%, with a JSC of 27.17 mA/cm2, a VOC of 2.04 V, and an FF of 84.31%. These results suggest the proposed CH3NH3GeI3/CH3NH3SnI3 tandem design could pave the way for efficient, eco‐friendly, and cost‐effective PV cells in a near future.

Enhance the performance of dye-sensitized solar cells with effective compact layers and direct contact cell structure

Compact layers (CLs) characterized by dense structures play a crucial role in enhancing the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Previous studies focus on preparing CLs using a single precursor through one-step methods. In this study, the new CLs are prepared by sequentially depositing films using titanium tetrachloride and titanium diisopropoxide bis(acetylacetonate) via chemical bath deposition and spray pyrolysis, respectively. Scanning electron microscope images show that the resulting CL has a denser structure compared to those prepared by one-step methods. Moreover, electrochemical impedance analysis indicates that they can efficiently inhibit charge recombination at the interface, leading to higher PCE. Furthermore, when the CL and direct contact (DC) structure are applied simultaneously to fabricate the DSSCs using Y123 dye and Co2+/3+ electrolyte, efficiencies of 9.86 % and 24.74 % can be obtained respectively, under one-sun and room light conditions (200 lx). Additionally, tandem cells using the DC structure for both top and bottom cells can achieve an efficiency of 29.68 % under room light illumination of 200 lx.

Efficient Blade-Coated Wide-Bandgap and Tandem Perovskite Solar Cells via a Three-Step Restraining Strategy.

Blade-coating techniques have attracted significant attention for perovskite solar cells (PSCs)due to their high precursor utilization and simplicity. However, the power conversion efficiency (PCE) of blade-coated PSCs often lags behind that of spin-coated devices, mainly due to difficulties in precisely controlling perovskite film formation during pre-nucleation, heterogeneous nucleation, and crystallization in the blade-coating and N2-knife drying processes. In this work, a three-step restraining strategy is introduced utilizing functional glycine amide hydrochloride to regulate pre-nucleation clustering, suppress excessive heterogeneous nucleation, and decelerate crystallization, enabling comprehensive control of the perovskite film formation processes. This approach results in enlarged grains, reduced defect densities, and highly oriented crystalline wide-bandgap perovskite films with significantly prolonged carrier lifetimes, achieving a maximum PCE of 19.97% for 1.77 eV-bandgap blade-coated PSCs. Furthermore, two-terminal tandem cells, composed of wide-bandgap perovskite top cells and 1.25 eV-bandgap perovskite bottom cells fabricated via blade coating, yield an impressive PCE of 27.11% (stabilized at 26.87%). This study offers comprehensive insights into controlling pre-nucleation, heterogeneous nucleation, and crystallization during blade coating, providing valuable guidance for developing high-performance, large-area devices in the future.

Numerical Analysis of Flow in U-Type Solid Oxide Fuel Cell Stacks

Numerical analysis of a U-type solid oxide fuel cell stack was performed using computational fluid dynamics to investigate the effects of stack capacities and fuel/air utilization rates on the internal flow uniformity. The results indicated that increasing the fuel/air utilization rate improved the gas flow uniformity within the stack for the same stack capacity. The uniformity in the anode fluid domain was better than that in the cathode fluid domain. Furthermore, the flow uniformity within the stack was associated with the percentage of pressure drop in the core region of the stack. The larger the percentage of pressure drop in the core region, the more uniform the flow inside the stack. Additionally, under a fuel utilization rate of 75%, the computational results exhibited excessively high fuel utilization rates in the top cell of a 3 kWe stack, indicating a potential risk of fuel depletion during actual stack operation.

Design and analysis of inorganic tandem architecture with synergistically optimized BaSnS3 top and AgTaS3 bottom perovskite Sub-Cells

Perovskite materials are revolutionizing the solar cell (SC) industry, continually enhancing their properties and establishing a prominent photovoltaic technology. Among these, BaSnS3 (BTS) and AgTaS3 (ATS) stand out for their strong potential as absorber layers. These inorganic chalcogenide perovskites address the drawbacks of their organic counterparts, being both lead-free and non-toxic, thereby making them highly suitable for photovoltaic (PV) applications. The exploration of BTS and ATS as absorber layers in a tandem solar cell’s top and bottom cells has yielded remarkable outcomes. The innovative tandem solar cell design features a top cell structured as n-WS2/p-BaSnS3/p+-MoS2 and a bottom cell configured as n-WS2/p-AgTaS3/p+-GeS. This theoretical study using SCAPS-1D demonstrates a high efficiency of 42.57 % with a VOC of 2.03 V, a JSC of 23.29 mA/cm2, and an FF of 89.85 %. These impressive results are achieved with adjusted layer thickness, carrier doping and defect levels, highlighting the strong potential of BaSnS3 and AgTaS3 photoactive materials. The findings reveal the viability of innovative, all-inorganic perovskite-based tandem solar cells, offering a promising avenue for future sustainable and high-efficiency photovoltaic device technologies.

Assessing visual comfort for active building enclosures: a novel simulation workflow for environmentally active top lighting cells

This study examines the impact of top lighting cells in a low-latitude city. It hypothesizes that an environmentally active control system enhances indoor illuminance without causing glare. It proposes a parametric procedure based on three simulation stages using UDI/UDIavg, Image-based, and Imageless DGP. The first stage is a simplified approach for evaluating image-based simulations considering representative dates. The second stage uses the image-based results for selecting the most contributing motion parameters through a One-way Variance-based Sensibility Analysis. The third expands the system's complexity for grid-based year-round simulations. Results indicate tilt motion as the most contributing factor for daylight control. Furthermore, the cells supplement daylight indoors, rendering a minimal increase of approximately 30% of the hours within the adequate illuminance range compared to the base case with no zenithal opening. The system ultimately achieve 100% of the hours in compliance with the selected daylight thresholds without significantly increasing glare.

Spectral management and current matching optimization for high-efficiency perovskite-CIGS-SnS triple junction tandem solar cells

Low-cost materials are used in this work to make a triple-junction tandem solar cell (TSC). Two-step filtered spectrum and current matching techniques are used to design a perovskite-CIGS-SnS based TSC using a SCAPS-1D simulator. To design a TSC, the top cell (TC) is illuminated with a 1.5AM spectrum, and the unabsorbed spectrum of the TC is utilized for the middle cell (MC). Similarly, the unabsorbed spectrum of the MC is used to illuminate the bottom cell (BC). Additional merits of this work: the perovskite used is a two-dimensional Dion Jacobson (DJ) perovskite, which is more stable than conventional perovskites. The results show that current matching is obtained at active layer thickness (nm) of 365/600/100 for TC/MC/BC, respectively. The proposed solar cell shows a remarkable PV performance of 3.25 V VOC, 9.42 mA/cm2 JSC, 79.3 % FF and 24.27 % PCE.

Photovoltaic Efficiency Enhancement of Indium-Free Wide-Bandgap Chalcopyrite Solar Cells via an Aluminum-Induced Back-Surface Field Effect.

Wide-bandgap chalcopyrite materials are attractive candidates for a wide variety of energy conversion devices such as the top cell of tandem-type photovoltaic devices and photoelectrochemical water splitting hydrogen evolution devices. Nevertheless, simultaneous realization of high open circuit voltage (VOC) and high fill factor (FF) values has been challenging, and thus, the photovoltaic performance has been limited. In this article, high VOC and high FF values of wide-gap chalcopyrite CuGaSe2 thin-film solar cells are simultaneously demonstrated using an aluminum-induced back-surface field effect. An independently certified photovoltaic efficiency of 12.25% was obtained from an elemental In-free CuGaSe2:Al (bandgap energy ∼1.7 eV) solar cell (VOC: 0.959 V, short circuit current density: 17.64 mA cm-2, FF: 72.5%). In addition, an over 1 V-VOC CuGaSe2 cell (FF: 74.5%) was obtained even with the use of a conventional CdS buffer layer. Although incorporation of aluminum often leads to degradation of the chalcopyrite solar cell performance, the addition of a small amount of aluminum is found to be effective in enhancing wide-gap chalcopyrite photovoltaic performance.

Halogenated Polycyclic Aromatic Hydrocarbon for Hole Selective Layer/Perovskite Interface Modification and Passivation for Efficient Perovskite‐Organic Tandem Solar Cells with Record Fill Factor

AbstractPerovskite whentandemed with organic photovoltaics (OPV) for double‐junctions have efficiencypotentials over 40%. However, there is still room for improvement suchas better current matching, higher fill factor, as well as lower voltage and fill factor losses in the top perovskite cell. Here weaddress the issue associated with the top perovskite cell by utilising anovel halogenated polycyclic aromatic hydrocarbon compound, 1‐naphthylammoniumchloride (NA─Cl) playing dual roles of surface modification for the hole selectivelayer (HSL) and passivation of HSL/perovskiteinterface. Results of X‐ray photoelectron spectroscopy and density functionaltheory calculations reveal that NA─Cl retains self‐assembly property for the HSLwhile demonstrating high dipole moment and polarizability. This induces asurface dipole at the HSL/perovskite interface reducing the energetic barrierfor hole extraction by 210 meV thereby enhancing voltage output and fill factorof the device. Such scheme when implemented in a high bandgap (1.78 eV)perovskite solar cell, results in a respectable efficiency of 19.7% and thehighest fill factor of 85.4% amongst those of 1.78 eV perovskite cells reported.We have also achieved 23% cell efficient monolithic perovskite‐OPV tandem withan impressive fill factor of 84%, which is the highest for perovskite‐OPVtandem cells reported to‐date.

Design for Increased Defect Tolerance in Metamorphic GaAsP-on-Si Top Cells

Design for Increased Defect Tolerance in Metamorphic GaAsP-on-Si Top Cells

Perovskite/Silicon Tandem Solar Cells Above 30% Conversion Efficiency on Submicron-Sized Textured Czochralski-Silicon Bottom Cells with Improved Hole-Transport Layers.

In perovskite/silicon tandem solar cells, the utilization of silicon heterojunction (SHJ) solar cells as bottom cells is one of the most promising concepts. Here, we present optimization strategies for the top cell processing and their integration into SHJ bottom cells based on industrial Czochralski (Cz)-Si wafers of 140 μm thickness. We show that combining the self-assembled monolayer [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with an additional phosphonic acid (PA) with different functional groups, can improve film formation when used as a hole transport layer improving wettability, minimizing shunt fraction and reducing nonradiative losses at the buried interface. Transient surface photovoltage and transient photoluminescence measurements confirm that the combined Me-4PACz/PA layer has similar charge transport properties to Me-4PACz alone. Moreover, this work demonstrates the potential for thin, double-side submicron-sized textured industry-relevant silicon bottom cells yielding a high accumulated short-circuit current density of 40.2 mA/cm2 and reaching a stabilized power conversion efficiency of >30%. This work paves the way toward industry-compatible, highly efficient tandem cells based on a production-compatible SHJ bottom cell.

Tuning Perovskite Crystal Growth Dynamics Using Additives on Textured Silicon Substrates

Double‐sided textured silicon solar cells with micrometer‐sized pyramid structure are used as bottom cells in monolithic tandem structures to decrease reflection losses. As top cell material, frequently perovskites are used. In this work, various additives are investigated to enhance the perovskite absorber quality, as a top cell fabricated using the hybrid route. In the context of the hybrid route, it is found that urea or methylammonium chloride (MACl) can effectively increase the grain size and improve the absorber quality, while formamidinium chloride (FACl) cannot. With urea, the crystallization can be tuned without leaving any voids in the film (unlike MACl). However, when annealed at a high annealing temperature, the excessive crystal growth with urea causes non‐conformal coating and high defect density. By adjusting the annealing conditions and additive concentration, the crystal growth of the perovskite top cell on the micrometer‐sized silicon pyramids can be fine‐tuned, ensuring that the perovskite layer conformally coated the pyramids. The use of additives not only improves crystallization but also enhances the conversion of the inorganics, particularly at the hole transport layer (HTL) interface. Moreover, this work contributes to a better understanding of perovskite crystallization dynamics and how to control it, especially on textured substrates.

Efficient wide-bandgap perovskite photovoltaics with homogeneous halogen-phase distribution

Wide-bandgap (WBG) perovskite solar cells (PSCs) are employed as top cells of tandem cells to break through the theoretical limits of single-junction photovoltaic devices. However, WBG PSCs exhibit severe open-circuit voltage (Voc) loss with increasing bromine content. Herein, inhomogeneous halogen-phase distribution is pointed out to be the reason, which hinders efficient extraction of carriers. We thus propose to form homogeneous halogen-phase distribution to address the issue. With the help of density functional theory, we construct a double-layer structure (D-2P) based on 2-(9H-Carbazol-9-yl)ethyl]phosphonic acid molecules to provide nucleation sites for perovskite crystallization. Homogeneous perovskite phase is achieved through bottom-up templated crystallization of halogen component. The efficient carrier extraction reduces the Shockley-Read-Hall recombination, resulting in a high Voc of 1.32 V. As a result, D-2P-treated device (1.75 eV) achieves a record power conversion efficiency of 20.80% (certified 20.70%), which is the highest value reported for WBG (more than 1.74 eV) PSCs.

Improving current-matching in textured perovskite/silicon tandem solar cells via a thickness control strategy

This study presents an analysis of a two-terminal tandem solar cell that integrates metal-doped, lead-free double Cs2AgBi0.75Sb0.25Br6 perovskite with silicon to enhance overall energy conversion efficiency. This study explores how the thicknesses of the top and bottom sub-cells affect current-matching in two-terminal tandem perovskite/silicon solar cells with two separate planar and textured configurations. Using numerical modeling in MATLAB, and considering dominant recombination effects, we calculated the performance parameters of the device. We investigated the optical and electrical properties of textured tandem structures, focusing on current- matching and the influence of layer thickness on device performance. Given the complexity, time, and expense involved in constructing tandem solar cells, being able to analytically determine the thickness at which current-matching occurs can be highly advantageous. This approach offers the benefit of providing a precise analytical relationship for this purpose. Our findings demonstrate that increasing the top cell thickness enhances current density and power conversion efficiency, but at the cost of the bottom cell’s efficiency due to increased light absorption. Moreover, we discovered a nearly linear behavior between the thickness of the top and bottom cells for achieving current-matching. The study highlights the critical balance required to optimize layer thicknesses, thereby improving the design and performance of tandem solar cells. These insights are significant as they pave the way for more efficient and cost-effective tandem solar cell designs in the future, potentially accelerating the adoption of advanced photovoltaic technologies. The results show good agreement with experimental data, validating our model.

Performance Enhancement of Hole Transport Layer-Free Carbon-Based CsPbIBr2 Solar Cells through the Application of Perovskite Quantum Dots.

CsPbIBr2, with its suitable bandgap, shows great potential as the top cell in tandem solar cells. Nonetheless, its further development is hindered by a high defect density, severe carrier recombination, and poor stability. In this study, CsPbI1.5Br1.5 quantum dots were utilized as an additive in the ethyl acetate anti-solvent, while a layer of CsPbBr3 QDs was introduced between the ETL and the CsPbIBr2 light-harvester film. The combined effect of these two QDs enhanced the nucleation, crystallization, and growth of CsPbIBr2 perovskite, yielding high-quality films characterized by an enlarged crystal size, reduced grain boundaries, and smooth surfaces. And a wider absorption range and better energy band alignment were achieved owing to the nano-size effect of QDs. These improvements led to a decreased defect density and the suppression of non-radiative recombination. Additionally, the presence of long-chain organic molecules in the QD solution promoted the formation of a hydrophobic surface, significantly enhancing the long-term stability of CsPbIBr2 PSCs. Consequently, the devices achieved a PCE of 9.20% and maintained an initial efficiency of 85% after 60 days of storage in air. Thus, this strategy proves to be an effective approach for the preparation of efficient and stable CsPbIBr2 PSCs.

One-Stone-for-Multiple-Birds Additive Strategy for Highly Efficient and Stable Carbon-Based Hole-Transport-Layer-Free CsPbI2Br Solar Cells.

During fabrication and operation of perovskite solar cells (PSCs), defects commonly arise within the crystals as well as at grain boundaries. However, conventional additive strategies typically only serve to mitigate the occurrence of a single defect and fail to significantly enhance device performance. Herein, carbon-based hole-transport-layer-free CsPbI2Br devices are focused on, one kind of important PSCs with more stable structure and an appropriate bandgap for a semitransparent solar cell or a top cell in a tandem configuration, and present a highly efficient one-stone-for-multiple-birds additive strategy based on lanthanide trifluoromethanesulfonates (Ln(OTF)3, Ln: neodymium (Nd), europium (Eu), dysprosium (Dy), thulium (Tm)). Density functional theory calculations reveal that the Ln3+ ions with a smaller radius can elevate defect formation energy for Pb and I vacancies within the crystals, while the presence of OTF- can effectively passivating uncoordinated Pb2+ at grain boundaries. In addition, Ln(OTF)3 addition increases the grain size and meanwhile reduces the surface roughness of the CsPbI2Br layers. All these positive contributions lead to a significant enhancement in power conversion efficiency (PCE) to 15.13% which is among the top PCEs reported for the corresponding solar cells, from 11.80% of the pristine device without Tm(OTF)3 addition, while notably boosting long-term stability and reducing current-voltage hysteresis.

Immunophenotyping schizophrenia subtypes stratified by antipsychotic response

Immune dysfunction has been proposed to play a role in the pathophysiology behind the development and persistence of psychosis. Current immunophenotyping studies are limited by small sample sizes and the number of immune markers investigated. Pharmacological subtypes in schizophrenia based on antipsychotic response have been proposed, but few studies have investigated immunophenotypes in treatment-resistant schizophrenia. In this study, we perform comprehensive immunophenotyping on 196 subjects comprising 147 schizophrenia patients stratified by antipsychotic response (49 antipsychotic-responsive, 70 clozapine-responsive, 28 clozapine-resistant) and 49 healthy controls. We aim to identify significant immune cell populations associated with schizophrenia and increasing treatment resistance, as potential modulators of underlying psychosis and/or treatment response. Patients with schizophrenia were recruited and assessed on the Clinical Global Impression – Schizophrenia (CGI-SCH). Treatment response was defined as a rating of three (mild severity) or less on the CGI-SCH positive symptom item after at least 8 weeks of adequate antipsychotic or clozapine treatment. Peripheral blood mononuclear cells were collected and flow cytometry was performed to identify 66 immune cell populations. Differences in cell population proportions were compared between schizophrenia cases and controls, and across all 4 groups, with post-hoc pairwise comparisons. Mucosal-associated invariant T (MAIT) cells (specifically CD8 + and DN double-negative subsets), total, exhausted and memory CD8 + T cells, VD1 + ϒδ T cells, plasmablasts, IgG + B cells and conventional dendritic cells 2 (cDC2) were among the top cell populations downregulated in schizophrenia. We observed increased downregulation with increasing treatment resistance. Conversely, naïve and exhausted CD4 + T cells, CD4/CD8 ratio and CCR5 + CCR2 + HLA DR + Myeloid cells were found to be upregulated in schizophrenia — we observed increased upregulation with increasing treatment resistance. We show significant immunophenotypic differences between schizophrenia cases and healthy controls, and consistent trend differences across varying degrees of antipsychotic resistance. We also examined immune cell populations not previously reported in schizophrenia. Future studies may explore immune markers identified as potential biomarkers of treatment resistance, and clarify on the relationship between immunological changes and pharmacological subtypes in schizophrenia.

A Prediction of All-Inorganic Lead-Free Halide Perovskites for Photovoltaic Application: Rb3Mo2Br9 and Rb3Mo2Cl9.

Lead-based organic-inorganic hybrid perovskites show promise as photovoltaic materials due to their high energy conversion efficiencies. However, concerns regarding lead toxicity and the poor environmental and operational stability of the organic cationic group have limited their widespread application. To address these challenges, the design of all-inorganic lead-free halide perovskites offers potential solutions for photovoltaic applications. Here, two layered perovskite derivatives, Rb3Mo2Cl9 and Rb3Mo2Br9, are explored, and their electronic, structural, and photovoltaic properties are analyzed using advanced theoretical calculations. Rb3Mo2Br9 exhibits a suitable direct bandgap of 1.60eV, making it a promising candidate for use as a light absorber in low-cost, high-efficiency solar cells. On the other hand, Rb3Mo2Cl9 demonstrates a wide direct bandgap exceeding 1.70eV, positioning it as a viable option for use as a top cell in tandem photovoltaic systems alongside silicon. Both materials display ideal optical properties in the visible light region and hold promise as excellent inorganic lead-free perovskite alternatives.

Effect of Ga Variation on the Bulk and Grain‐Boundary Properties of Cu(In,Ga)Se2 Absorbers in Thin‐Film Solar Cells and Their Impacts on Open‐Circuit Voltage Losses

ABSTRACTPolycrystalline widegap Cu(In,Ga)Se2 (CIGSe) absorbers for top cells in photovoltaic tandem devices can be synthesized via [Ga]/([Ga] + [In]) (GGI) ratios of > 0.5. However, the power conversion efficiencies of such high‐GGI devices are smaller than those of the record cells with GGI < 0.5. In the present work, the effects of the GGI ratio on various CIGSe material properties were studied and correlated with the radiative and nonradiative open‐circuit voltage (VOC) deficits of the thin‐film solar cells. Average grain sizes, grain boundary (GB) recombination velocities, fluctuations in luminescence energy distribution, barrier heights at GBs, effective electron lifetimes, and Urbach energies were investigated in five solar cells with GGI ratios from 0.13 to 0.83. It was found that the GGI variation affects GB recombination velocities, fluctuations in spatial luminescence distributions, the average grain size, the electron lifetime, and the Urbach energy. In contrast, the detected ranges of barrier heights at GBs are independent of the GGI ratio. Mainly Ga/In gradients give rise to substantial radiative VOC losses in all solar cells. Nonradiative VOC deficits are dominant especially for solar cells with GGI > 0.5, which can be attributed to low bulk lifetimes and enhanced recombination at GBs in CIGSe absorbers in this compositional range.