Planar Perovskite Solar Cells Research Articles

Thermal Stability Analysis of Formamidinium–Cesium‐Based Lead Halide Perovskite Solar Cells Fabricated under Air Ambient Conditions

The instability of perovskite solar cells (PSCs) remains a major bottleneck for their commercialization, with thermal instability posing a major concern, given the inevitable presence of heat in photovoltaic devices. Mixed‐cation/halide perovskites demonstrate enhanced stability and efficiency compared to single‐cation/halide perovskites. Identifying the optimal perovskite composition capable of withstanding high temperatures for longer durations is crucial for the development of thermally stable PSCs. This study provides valuable insights into the optimization of mixed‐cation/halide perovskites to enhance the thermal and structural stability of perovskite films. By systematically varying the Cs content in FA1−yCsyPb(I0.85Br0.15)3 (0 < y < 25)‐based perovskite, it is observed that controlling the Cs content allows precise modulation of crystal orientation in perovskite film with 10% Cs obtained as the optimal value. The perovskite film containing 10% Cs not only exhibits reduced microstrain but also demonstrates enhanced thermal stability during testing at 85 °C under controlled humidity. Furthermore, planar PSCs are fabricated using FA0.90Cs0.10Pb(I0.85Br0.15)3 as the absorber layer and TOP‐3 as the hole‐transporting material, achieving a promising power conversion efficiency (PCE) of 17.70%. Impressively, the unencapsulated devices retain 95% of their initial PCE after 1000 h of dark storage under ambient conditions.

The Prospects and Challenges for Ambi‐Polar Vacancy‐Ordered Double Perovskite Cs2SnI6 towards Realization of High Efficiency Air‐Stable Solar‐Cells

The rapid advancements in material research for lead‐free inorganic metal halide perovskites have fuelled the pathway to design environmentally‐benign solar‐cells to cater the energy requirements for future generations. The vacancy‐ordered double perovskite Cs2SnI6 with an optimum band‐gap (∽1.3 eV), high absorption coefficient (∽105 cm‐1), ambi‐polar charge carrier transport, high structural and compositional stability coupled with simple cost‐effective solution‐based synthesis techniques seems to be an excellent candidate to design air‐stable high‐efficiency solar‐cell based applications. The review focusses on the structure‐property relationship in Cs2SnI6; and its critical dependency on growth precursors, conditions and methods. The recent advancements in material and additive engineering to obtain phase‐pure uniform continuous smooth Cs2SnI6 films; and myriad methods to modulate its opto‐electronic properties are summarized. The nature, origin and type of charge‐carriers in intrinsic and doped Cs2SnI6 is extensively discussed. The application of Cs2SnI6 in dye sensitized solar‐cell (DSSC) and planar perovskite solar‐cell (PSC) configurations are critically reviewed; and its recent progress and challenges to achieve ultimate theoretical Shockley‐Queisser limit of 30‐33% is presented. The recent experimental findings on the stability and performance of Cs2SnI6‐based solar‐cells under ambient and controlled conditions would be discussed to highlight its feasibility for the design and development of air‐stable high‐efficiency solar‐cells.This article is protected by copyright. All rights reserved.

Self-Heating of Planar Perovskite Solar Cells Depending on Active Material Properties

Self-Heating of Planar Perovskite Solar Cells Depending on Active Material Properties

Asymmetrical benzothiadiazole core-based hole transport materials for planar perovskite solar cell

For the purpose of fabricating high performance hole transport materials (HTMs) for n-i-p planar perovskite solar cells (PSCs), two asymmetric and one symmetric structured donor-acceptor-donor (D-A-D) type small molecules (a-BTC, a-BTBC and BTDC) were synthesized by introducing two different peripheral groups toward benzothiadiazole core. The a-BTBC with longer π conjugation lengths shows good film formation property, higher hole mobility and conductivity, and achieves power conversion efficiency (PCE) of 23.5 %. It can retain 80 % of the initial PCE after aging 30 days in an ambient condition with relative humidity of 40–60 %. Our results show the potential and provides reference for molecular design of asymmetric structured HTMs.

Managing Interfacial Defects and Charge-Carriers Dynamics by a Cesium-Doped SnO2 for Air Stable Perovskite Solar Cells.

A high-quality nanostructured tin oxide (SnO2) has garnered massive attention as an electron transport layer (ETL) for efficient perovskite solar cells (PSCs). SnO2 is considered the most effective alternative to titanium oxide (TiO2) as ETL because of its low-temperature processing and promising optical and electrical characteristics. However, some essential modifications are still required to further improve the intrinsic characteristics of SnO2, such as mismatch band alignments, charge extraction, transportation, conductivity, and interfacial recombination losses. Herein, an inorganic-based cesium (Cs) dopant is used to modify the SnO2 ETL and to investigate the impact of Cs-dopant in curing interfacial defects, charge-carrier dynamics, and improving the optoelectronic characteristics of PSCs. The incorporation of Cs contents efficiently improves the perovskite film quality by enhancing the transparency, crystallinity, grain size, and light absorption and reduces the defect states and trap densities, resulting in an improved power conversion efficiency (PCE) of ≈22.1% with Cs:SnO2 ETL, in-contrast to pristine SnO2-based PSCs (20.23%). Moreover, the Cs-modified SnO2-based PSCs exhibit remarkable environmental stability in a relatively higher relative humidity environment (>65%) and without encapsulation. Therefore, this work suggests that Cs-doped SnO2 is a highly favorable electron extraction material for preparing highly efficient and air-stable planar PSCs.

TiO2 Electron Transport Layer with p–n Homojunctions for Efficient and Stable Perovskite Solar Cells

HighlightsDeveloping a universal strategy of the p–n homojunction engineering that could significantly boost electron mobility of electron transport layer (ETL) by two orders of magnitude.Proposing a new mechanism based on p–n homojunction to explain inhibited carrier loss at buried interface.Setting a new performance benchmark as high as 25.50% for planar perovskite solar cells employing TiO2 as ETLs.

Multifunctional buried interface modification of SnO2-based planar perovskite solar cells via phosphorus hetero-phenanthrene flame retardants

Tin dioxide (SnO2) is widely utilized for the cost-effective electron transport layer (ETL) in perovskite solar cells (PSCs) owing to its excellent optoelectronic properties. However, the surface defect states present in SnO2 ETL prepared by conventional solution methods seriously hinder the further improvement of device photovoltaic performance. It is urgently essential to develop a facile strategy to effectively minimize the adverse effects of SnO2 ETL on PSCs. Herein, a phosphorus hetero-phenanthrene flame retardant, DOPO, is introduced as a multifunctional surface modifier to improve the interfacial properties between SnO2 ETL and perovskite. Through systematic characterization analysis, the PO group in DOPO not only passivates the defective states on the surface of SnO2 ETL, but also provides chemical chelation sites for the uncoordinated Pb2+ ions in the upper perovskite structure to improve the film crystalline quality. Eventually, the photoelectric conversion efficiency (PCE) of the optimized device is improved from an initial 19.74 %–22.57 %, along with significantly improved device stability. This work provides an important reference for the development of new multifunctional interface modification materials required for SnO2-based planar PSCs with excellent properties.

Improved performance of inorganic CsPbI3 perovskite solar cells with WO3/C60 UTL bilayer as an ETL structure: a computational study

CsPbI3, also known as cesium lead iodide, has garnered significant attention as a potential absorber in perovskite solar cells (PSCs). CsPbI3-PSCs have not matched the high performance of hybrid PSCs. This study aimed to identify an effective combination of charge transport layers. Six-hole transporting layers (HTLs) including Spiro-OMeTAD, Cu2O, CuO, CuAlO2, CuSbS2, and SrCu2O2, as well as five electron transporting layers (ETLs) such as TiO2, WO3, ZnO, IGZO, and CdZnS, were tested separately in 30 PSCs. The findings of this research indicate that CuAlO2 as the HTL and WO3 as the ETL that are the most appropriate materials among the options examined, so we use FTO/WO3/CsPbI3/CuAlO2/Au as a required PSC. In this research, we used SCAPS (Solar Cell Capacitance Simulator)−1D device modeling to investigate the bilayer ETL of inorganic CsPbI3-PSC and discover the methods to improve their efficiency. In planar PSCs, optimizing electron–hole pair extraction and recombination at the ETL/perovskite interface is crucial for achieving high performance. The key concept is to enhance the WO3/perovskite interface properties by adding a 5 nm ultra-thin layer (UTL) of C60. The bilayer structure WO3/C60 was found to have the advantage of high electron extraction and low interfacial recombination, primarily due to more effective energy level alignment and defect passivation. To achieve the superior efficiency of PSC, various factors such as defect and doping densities in all layers, the energy level alteration of ETL and HTL, interface defect densities on both ETL and HTL sides, back metal contact, operating temperature, and parasitic resistances were optimized. After optimizing these parameters, the efficiency of the system containing WO3/C60 bilayer ETL was found to be 29.39%. The current work proposes a straightforward and promising method to create photovoltaic devices, especially for many types of perovskites, with desirable charge transport layers and recombination properties.

Benzalkonium chloride modification of tin oxide to enhance the performance of perovskite solar cells

For planar perovskite solar cells (PSCs), tin oxide (SnO2) is a perfect electron transport material. However, owing to nanoparticle agglomeration and defects, the advantages of SnO2 cannot be effectively utilized. Herein, a cationic surfactant, benzalkonium chloride (BAC) is introduced into SnO2 precursor solution to prevent the aggregation of SnO2. Thus, a uniform and free of pinhole SnO2 electron transport layer (ETL) is obtained, which supports the formation of high-quality perovskite layer (PVK). The introduction of BAC adjusts the energy level of ETL and improves the electron transport in the buried interface. Moreover, the BAC-modification reduces and passivates the defects on the surface of SnO2 and perovskite films. Consequently, BAC-modified PSCs achieves a champion efficiency of 23.49 % with an impressive fill factor of 84.50 %. The unpackaged device maintains an initial efficiency of 91.4 % after 1000 h of storage in dark at 25 ± 5 °C and 25 ± 5 % relative humidity.

Broadband enhancement of SiO2@TiO2 light-trapping nanostructure for improving the efficiency of perovskite solar cells

High-efficiency perovskite solar cells (PSCs) are one of the promising candidates to solve the energy crisis worldwide. Optical loss is one of the factors limiting the efficiency of PSCs and antireflection layers provide a dependable method for improving the efficiency of PSCs. Here, a design and optimization of PSCs with a SiO2@TiO2 nanoparticles (NPs) antireflection layer is systematically studied by COMSOL Multiphysics. The effect of different shell-thickness ratios (STRs) on the average light absorption and short-circuit current density of PSCs is simulated and compared with that of planar PSCs. The results show that the average light absorption of PSCs with SiO2@TiO2 NPs of 0.08 STR is 83.21%, which is 5.17% higher than that of PSCs with SiO2 NPs and 10.11% higher than that of planar PSCs. Our results provide theoretical guidance for using SiO2@TiO2 NPs as antireflection layers in the fabrication of PSCs.

Band alignment studies of Zn1-xNixO/ZnO: As bilayer electron transport layer in perovskite solar cells

An efficient electron transport layer (ETL) is an essential requirement for performance and stability for perovskite solar cells. In this study, we have opted Zn1-xNixO/ZnO bilayer as is used electron transport layer instead of the ZnO single layer to overcome the trap-assisted recombination and also to enhance energy level alignment in the solar cell. For this, pristine ZnO and Ni-doped ZnO (Ni–ZnO) thin films were deposited on fused silica (Quartz) by pulsed laser deposition (PLD). For confirmation of the structural properties of deposited thin films, X-ray diffraction has been used. Electron affinity and band gap of these films have been evaluated by UPS and UV–Vis spectroscopy to design Zn1-xNixO/ZnO bilayer ETL. Further, planar perovskite solar cell has been schematized and simulated using SCAPS-1D software using experimentally designed bilayer ETL.

Fabricating Planar Perovskite Solar Cells through a Greener Approach.

High-quality perovskite thin films are typically produced via solvent engineering, which results in efficient perovskite solar cells (PSCs). Nevertheless, the use of hazardous solvents like precursor solvents (N-Methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), gamma-butyrolactone (GBL)) and antisolvents (chlorobenzene (CB), dibutyl ether (DEE), diethyl ether (Et2O), etc.) is crucial to the preparation of perovskite solutions and the control of perovskite thin film crystallization. The consumption of hazardous solvents poses an imminent threat to both the health of manufacturers and the environment. Consequently, before PSCs are commercialized, the current concerns about the toxicity of solvents must be addressed. In this study, we fabricated highly efficient planar PSCs using a novel, environmentally friendly method. Initially, we employed a greener solvent engineering approach that substituted the hazardous precursor solvents with an environmentally friendly solvent called triethyl phosphate (TEP). In the following stage, we fabricated perovskite thin films without the use of an antisolvent by employing a two-step procedure. Of all the greener techniques used to fabricate PSCs, the FTO/SnO2/MAFAPbI3/spiro-OMeTAD planar device configuration yielded the highest PCE of 20.98%. Therefore, this work addresses the toxicity of the solvents used in the perovskite film fabrication procedure and provides a promising universal method for producing PSCs with high efficiency. The aforementioned environmentally friendly approach might allow for PSC fabrication on an industrial scale in the future under sustainable conditions.

Analysis of Inverted Planar Perovskite Solar Cells with Graphene Oxide as HTL using L9 OA Taguchi Method

In this work, the Taguchi Method approach is used to optimize graphene oxide (GO) as the hole transport layer (HTL) in inverted perovskite solar cells (IPSC). By using this method, the data from the numerical modelling Solar Cell Capacitance Simulator-One Dimensional (SCAPS-1D) was optimized. While it has distinct parameter results and diverse causes, it also takes a long time to complete the analysis process. The Taguchi method is reported to be able to find the most significant factor and reduce the parameter variations in less time. The Taguchi algorithm is used in this experiment because it is based on orthogonal array (OA) experiments, which provide a substantially smaller variance for the experiment with optimal control parameter values. SCAPS-1D software was used to simulate the IPSC with GO as HTL. The results obtained with the software are then analysed and compared with the performance of the solar cell. The final results show that the Taguchi Method optimized IPSC with GO as HTL achieved better Power Conversion Efficiency (PCE) compared to previous researchers, with the efficiency increasing from 18.53%.to 23.408%.

Ammonium iodide-incorporated SnO2 obtains perovskite solar cells with over 24% efficiency

Tin dioxide (SnO2) as the most promising electron transport layer (ETL) has been widely used in high-efficiency perovskite solar cells (PSCs) due to its excellent optical/electronic properties, chemical stability, and low-temperature processing. However, the surface of SnO2 ETL contains defect sites, which result in energy losses in PSCs. In order to passivate the defects of SnO2 surface and together tune the electronic properties of SnO2 ETL for getting high-performance PSCs, we herein incorporate the low-cost material ammonium iodide (NH4I) into the SnO2. After the NH4I doping, the optimized photovoltaic power conversation efficiency is significantly enhanced (the highest efficiency can reach 24.4%), the hysteresis of device is largely suppressed to a negligible level, and the stability of device is also obviously improved. The origin of these enhancements is further disclosed by the positive effects of NH4I doping on both ETL and perovskite film: the surface morphology of ETL is effectively flatten, the energy level of ETL is suitably adjusted, the electron mobility of ETL and the perovskite grain size are clearly increased, the surface defects of ETL and the trap states in the perovskite film are greatly reduced, and the PbI2 residue in the perovskite layer is obviously diminished. The study here of incorporating cheap inorganic small molecule in the ETL provides an ingenious way to enhance the performance of the planar PSCs.

Passivating defects in SnO2 electron transport layer through SnF2 incorporation in perovskite solar cells

Metal halide perovskite solar cells have received a lot of attention from researchers because of their excellent performance, and their efficiency has increased rapidly over the past decade and is now comparable to that of conventional crystalline silicon solar cells. Perovskite solar cells (PSCs) are currently most commonly constructed with SnO2 as an electron transport layer (ETL). Nevertheless, its existence of bulk phase defects and surface defects pose an impediment to developing a higher level as the most favorable electron transport layer. This paper suggests an efficient technique to decrease the defects of SnO2 through incorporating a metal halide SnF2 in planar (n-i-p type) perovskite solar cells. Divalent Sn in SnF2 is easily oxidized to tetravalent Sn, leading to more conversion of divalent Sn to tetravalent Sn, which inhibits the formation of oxygen vacancies from the source. F replaces defective sites, passivates oxygen vacancy defects, and reduces the content of hydroxyl oxygen on the surface. Doping SnF2 enhances the conduction band value and conductivity of SnO2, making the energy levels of the ETL and perovskite interfaces more compatible. This eliminates energy barriers in charge transport. Consequently, the fill factor of planar PSCs that were prepared through SnO2:SnF2 ETL exhibited an increase from 80.01% to 82.12%. Furthermore, the efficiency of PCE underwent an improvement from 21.43% to 22.65%.

Fabrication of Highly Efficient and Ambient Stable Planar MAPbI3 Perovskite Solar Cells via Defect Passivation through Crosslinking Strategy

Iodine‐based hybrid planar perovskite solar cells’ (PSCs) overall performance is still very limited. In this work, a highly functionalized iodine‐based hybrid perovskite layer is fabricated by incorporating trimethylolpropane ethoxylated triacrylate (TET) within the perovskite precursor, which can crosslink with the grain boundaries to improve the crystallinity as well as the grain size and passivate the defect states of the perovskite material. The MAPbI3‐based thin films with TET exhibited large grain sizes from 195.73 to 587.49 nm with 8 mg mL−1 of TET concentration. The X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X‐ray (EDX) elemental mapping, photoluminescence (PL), and time resolved photoluminescence (TRPL) characterization results suggest the strong crosslinking effect between TET and MAPbI3, which improves the crystallinity and reduces the charge trap density. Planar PSCs is fabricated with the device architecture fluorine‐doped tin oxide (FTO)/c‐TiO2/MAPbI3:TET/Spiro‐MeOTAD/Au and achieved a power conversion efficiency (PCE) of 14.75% under 1.5 AM light illumination. The fabricated PSCs shows excellent ambient stability which retains 80% of their PCE after being exposed to the ambient environment of relative humidity (RH) ≈60%, room temperature (RT) ≈27 °C without any encapsulation.

Mathematical Modeling and Optimization of Highly Efficient Nontoxic All-Inorganic CsSnGeI3-Based Perovskite Solar Cells with Oxide and Kesterite Charge Transport Layers.

Despite exceptional optoelectronic properties and rapidly increasing efficiency of perovskite solar cells (PSCs), the issues of toxicity and device instability have hampered the commercialization of this renewable energy technology. Lead (Pb) being the main culprit creates major environmental risks and therefore must be replaced with a nontoxic material such as tin (Sn), germanium (Ge), etc. Moreover, replacing organic cations in the perovskite's ABX3 structure with inorganic ones like cesium (Cs) helps aid the stability issues. This study uses six different kesterite-based hole transport layers (HTLs) and three different metal oxide-based electron transport layers (ETLs) to numerically simulate and optimize all-inorganic CsSnGeI3 PSCs. Metal oxide ETLs are used in this study due to their large band gap, while kesterite HTLs are used due to their excellent conductive properties. All of the simulations are performed under standard testing conditions. A total of 18 novel planar (n-i-p) PSCs are modeled by the combination of various charge transport layers (CTLs), and the device optimization was done to enhance the power conversion efficiencies (PCEs) of the PSCs. Furthermore, the effect of CTLs on the energy band alignment, electric field, quantum efficiency, light absorption, and recombination rate is analyzed. Additionally, a detailed analysis of the impact of defect density (Nt), interface defects (ETL/Perv, Perv/HTL), temperature, and work function on the functionality of 18 different CsSnGeI3-based PSCs is conducted. The simulation findings demonstrate that SnO2/CsSnGeI3/CNTS is the most efficient optimized PSC among all of the simulated structures, with a PCE of 27.33%, Jsc of 28.04 mA/cm2, FF of 85%, and Voc of 1.14 V.

Controlling surface morphology of Ag-doped ZnO as a buffer layer by dispersion engineering in planar perovskite solar cells

In recent years, the power conversion efficiency (PCE (%)) of perovskite solar cells (PSCs) has improved to over 26%. To enhance the photovoltaic properties of PSCs, several materials for the electron transport layer (ETL) have been investigated. Zinc oxide (ZnO) is a significant ETL due to its high electron mobility and optical transparency in PSCs. As a result of various deposition methods, ZnO ETL can be processed at low temperatures. On the other hand, based on several studies, metal-doped ZnO can facilitate electron transfer, thereby improving the performance of un-doped ZnO ETL-based PSCs. Here, to improve the PCE (%) and long-term stability of un-doped ZnO ETL-PSCs, silver (Ag)-doped ZnO 1wt% as a buffer layer is examined. In this paper, with the addition of an organic solvent (ethanol) to the dispersion of Ag-doped ZnO 1 wt% nanoparticles (NPs) in deionized (DI) water, the morphology of the buffer layer (Ag-doped ZnO 1 wt%) can be controlled. This approach focuses on reducing the wettability of the ZnO/Ag-doped ZnO 1 wt% bilayer ETLs and enhancing the stability of un-doped ZnO ETL-PSCs. According to the results, the ZnO/H2O-ethanol mixtures-Ag-doped ZnO 1 wt% bilayer ETL leads to the formation of high-quality perovskite with low defects, reducing the recombination rate, and long-term stability of un-doped ZnO ETL-PSCs in ambient conditions.

Oriented Molecular Bridge Constructs Homogeneous Buried Interface for Perovskite Solar Cells with Efficiency Over 25.3.

Buried interface optimization matters the efficiency improvement of planar perovskite solar cells (PSCs), and the molecular bridge is reported to be an effective approach. Herein, a molecular bridge is constructed at buried interface using 4-chloro-3-sulfamoylbenzoic acid (CSBA), and its preferred arrangement is systematically investigated. It is elucidated that the CSBA molecular is prone to be orientationally absorbed on TiO2 surface through COOH-Ti, and then connect with perovskite through S═O-Pb, resulting in a feasible oriented molecular bridge. Contributing to the passivated interfacial defects, optimized interfacial energy level, and released perovskite tensile stress, resulting from the oriented CSBA molecular bridge, the PSCs with an active area of 0.08 cm2 achieve a certified power conversion efficiency (PCE) of 25.32%, the highest among the TiO2-based planar PSCs. Encouragingly, the PSCs with an active area of 1 cm2 achieve a champion PCE of 24.20%, significantly promoting the efficiency progress of large-area PSCs. In addition, the PSCs with oriented CSBA molecular bridge possess enhanced stability, the unencapsulated PSCs can maintain ≈91% and ≈85% of their initial PCE after 3000 h aging under ambient condition and 1200 h aging under exposure to UV irradiation.

Universal Strategy with Structural and Chemical Crosslinking Interface for Efficient and Stable Perovskite Solar Cells

AbstractDue to the limited interface contact and weak interfacial interaction, planar heterojunction perovskite solar cells (PSCs) have space for further improvement. Herein, a structural and chemical crosslinking interface is proposed and constructed by introducing an extra layer, which blends tin dioxide (SnO2) nanoparticles with chloride salts. Since the incorporated materials can be dissolved during the fabrication of perovskite, the quality of perovskite films is improved, leading to larger grain size and reduced trap‐state density. Also, more chloride ions at the SnO2/perovskite interface are observed and the interaction between Cl− and Sn4+ is confirmed. It results in more pronounced n‐type SnO2 with better conductivity and deeper conduction bands, leading to preferable energy level alignment between SnO2 and perovskite. Consequently, the open‐circuit voltage and fill factor of the devices increase, and target cells present better stability, retaining 98% of initial efficiencies after >10 000 h storage in dry air (≈5% relative humidity) and maintaining 85.50% of the initial efficiency after 1000 h of operation under light. This strategy enables the achievement of 25.28% efficiency with a low bandgap (1.53 eV) perovskite composition, and it is confirmed to be universal when other related materials are utilized.