Tin-based Perovskite Solar Cells Research Articles

Repaired surface structural imperfection of tin Wide-Bandgap perovskite films for photovoltaic application

Tin-based perovskite solar cells (Sn-PSCs) are emerging as a potential alternative to lead-based PSCs in order to address issues of theoretical efficiency and toxicity limitations. However, due to the structural imperfections on the surface of perovskite films, the numerous defects can cause severe non-radiative recombination loss, which would reduce the efficiency and operational stability of Sn-PSCs. Herein, we used 4-fluorobenzoyl chloride (4FBC) for surface treatment of tin perovskite films. The introduction of 4FBC passivated the defects, improved the surface morphology, slowed down the formation of SnI2, suppressed the oxidation of Sn2+ from top to bottom, and improved the carrier mobility. Encouragingly, the treated device achieved a champion power conversion efficiency of 11.03 % and significantly improved the open-circuit voltage (VOC) to 0.94 V, the fill factor (FF) to 86.7 %, which both were the highest VOC and FF values reported in wide-bandgap Sn-PSCs (∼1.6 eV) to date. The findings emphasize the importance of surface treatment for tin halide perovskites and serve as a reference for further reducing the voltage loss in wide-bandgap Sn-PSCs.

Rational design and recent advancements of addictives engineering in ASnI3 tin-based perovskite solar cells: insights from experiments and computational

Additive engineering in tin-based perovskite solar cells. Insight from the experiment and computational.

Rational design of formamidine tin-based perovskite solar cell with 30% potential efficiency via 1-D device simulation.

As a promising photovoltaic technology, halide perovskite solar cells (PSCs) have recently attracted wide attention. This work presents a systematic simulation of low bandgap formamidinium tin iodide (FASnI3)-based p-n heterojunction PSCs to investigate the effects of multiple optoelectronic variations on the photovoltaic performance. The structures of the simulated devices are n-i-p, electron transport layer-free (ETL-free), hole transport layer-free (HTL-free), and inverted HTL-free. The simulation is conducted with the Solar Cell Capacitance Simulator (SCAPS-1D). The power conversion efficiencies (PCEs) dramatically decrease when the acceptor doping density (NA) of the absorber layer exceeds 1016 cm-3. For all devices, the photovoltaic parameters dramatically decrease when the absorber defect density (Nt) is over 1015 cm-3, and the best absorber layer thickness is 1000 nm. It should be pointed out that the Nt and the interface defect layer (IDL) are the primary culprits that seriously affect the device performance. When the interfacial defect density (Nit) exceeds 1012 cm-3, PCEs begin to decline significantly. Therefore, paying attention to these defect layers is necessary to improve the PCE. Furthermore, the proper conduction band offset (CBO) between the electron transport layer (ETL) and absorber layer positively affects PSCs' performance. These simulation results help fabricate highly efficient and environment-friendly narrow bandgap PSCs.

Enhancing the performance of tin-based perovskite solar cells through solvent purification of tin iodide

Tin (Sn)-based perovskites are very promising for the fabrication of low-toxicity lead-free perovskite solar cells (PSCs), but they suffer from easy oxidation of Sn2+to Sn4+which leads to poor performance.

Environmentally friendly anti-solvent engineering for high-efficiency tin-based perovskite solar cells

Pioneeringly, we point out a general principle for selecting an appropriate anti-solvent. Salting-out crystallization induced by a green anti-solvent (acetic acid, HAc) has been used for the first time to fabricate Sn-based PVSCs with an efficiency of 12.78%.

Situation and Perspectives on Tin-Based Perovskite Solar Cells

Perovskite solar cells have become the current research focus because of their high conversion efficiency and other advantages; however, the toxicity of lead used in them has raised environmental concerns. Tin-based perovskite materials have become the most promising alternative materials for perovskite solar cells because of their relatively low toxicity, suitable band gap and relatively higher energy conversion efficiency than perovskite materials based on other elements. In this article, the status of this rapidly growing field, authors’ output and cooperation, hot research topics, important references and the development trends of tin-based perovskite solar cells are identified and visualized using CiteSpace software. The main research fields are found to be optical properties, 3D–2D perovskite and perovskite solar cell conduction band materials. The mixed organic metal halide perovskite solar cell and the CsSnI3 semiconductor are identified as emerging trends for tin-based perovskite solar cells. Such contents in this article highlight the key points in the wide field of literature so it can be understood efficiently.

Computational Probing of Tin-Based Lead-Free Perovskite Solar Cells: Effects of Absorber Parameters and Various Electron Transport Layer Materials on Device Performance.

Tin-based perovskite solar cells have gained global research attention due to the lead toxicity and health risk associated with its lead-based analog. The promising opto-electrical properties of the Tin-based perovskite have attracted researchers to work on developing Tin-based perovskite solar cells with higher efficiencies comparable to lead-based analogs. Tin-based perovskites outperform lead-based ones in areas such as optimal band gap and carrier mobility. A detailed understanding of the effects of each parameter and working conditions on Tin-based perovskite is crucial in order to improve efficiency. In the present work, we have carried out a numerical simulation of a planar heterojunction Tin-based (CH3NH3SnI3) perovskite solar cell employing a SCAPS 1D simulator. Device parameters, namely, the thickness of the absorber layer, the defect density of the absorber layer, working temperature, series resistance, and metalwork function, were exclusively investigated. ZnO was employed as the ETL (electron transport layer) material in the initial simulation to obtain optimized parameters and attained a maximum efficiency of 19.62% with 1.1089 V open circuit potential (Voc) at 700 nm thickness (absorber layer). Further, different ETL materials were introduced into the optimized device architecture, and the Zn2SnO4-based device delivered an efficiency of 24.3% with a Voc of 1.1857 V. The obtained results indicate a strong possibility to model and construct better-performing perovskite solar cells based on Tin (Sn) with Zn2SnO4 as the ETL layer.

Simulation and Investigation of 26% Efficient and Robust Inverted Planar Perovskite Solar Cells Based on GA0.2FA0.78SnI3-1%EDAI2 Films.

A hybrid tin-based perovskite solar cell with p-i-n inverted structure is modeled and simulated using SCAPS. The inverted structure is composed of PEDOT:PSS (as hole transport layer-HTL)/GA0.2FA0.78SnI3-1% EDAI2 (as perovskite absorber layer)/C60-fullerene (as electron transport layer-ETL). Previous experimental studies showed that unlike conventional tin-based perovskite solar cells (PSC), the present hybrid tin-based PSC passes all harsh standard tests and generates a power conversion efficiency of only 8.3%. Despite the high stability that this material exhibits, emphasis on enhancing its power conversion efficiency (PCE) is crucial. To that end, various ETL and HTL materials have been rigorously investigated. The impact of energy level alignment between HTL/absorber and absorber/ETL interfaces have been elucidated. Moreover, the thickness and the doping concentration of all the previously mentioned layers have been varied to inspect their effect on the photovoltaic performance of the PSC. The optimized structure with CuI (copper iodide) as HTL and ZnOS (zinc oxysulphide) as ETL scored a PCE of 26%, which is more than three times greater than the efficiency of the initial structure. The current numerical simulation on GA0.2FA0.78SnI3-1% EDAI2 could greatly increase its chance for commercial development.

Early thermal aging detection in tin based perovskite solar cell

Tin-based perovskite solar cells (T-PSCs) are introduced as the next generation of valid and environment-friendly photovoltaic (PV) cells for near-future commercialization. However, there are some issues limiting T-PSCs including their instability, low efficiency, and use of toxic processing solvents. Among all these barriers, instability and early aging under thermal stress conditions are considered as significant challenges to the development of the T-PSCs. In this study, the impact of different temperature levels on the performance of a T-PSC is investigated over time. It is observed that early degradation of the device occurs at higher temperatures. For timely detection of the early aging, an accurate adaptive estimation of the series resistance is obtained in the equivalent single-diode circuit model of the T-PSC. It is shown that the trend of changes in the series resistance is a reliable indication of the aging process in the T-PSC. Finally, a mathematical index is derived for early aging detection based on the relative variation of the gradient from its minimum value in the linear regression analysis. The proposed approach could be utilized for timely detection of early aging conditions and protection of the device from permanent damage.

Chlorofullerene C60Cl6 Enables Efficient and Stable Tin‐Based Perovskite Solar Cells

Tin‐based perovskite solar cells (TPSCs) have received great attention due to their eco‐friendly properties and high theoretical efficiencies. However, the fast crystallization feature of tin‐based perovskites leads to poor film quality and limits the corresponding device performance. Herein, a chlorofullerene, C60Cl6, with six chlorine attached to the C60 cage, is applied to modulate the crystallization process and passivate grain boundary defects of the perovskite film. The chemical interactions between C60Cl6 and perovskite components retard the transforming process of precursors to perovskite crystals and obtain a high‐quality tin‐based perovskite film. It is also revealed that the C60Cl6 located at the surfaces and grain boundaries can not only passivate the defects but also offer a role in suturing grain boundaries to suppress the detrimental effects of water and oxygen on perovskite films, especially the oxidation of Sn2+ to Sn4+. As a result, the C60Cl6‐based device yields a remarkably improved device efficiency from 10.03% to 13.30% with enhanced stability. This work provides a new strategy to regulate the film quality and stability of TPSCs using functional fullerene materials.

Dopamine Hydrochloride-Assisted Synergistic Modulation of Perovskite Crystallization and Sn2+ Oxidation for Efficient and Stable Lead-free Solar Cells.

Tin perovskites have received great concern in solar cell research owing to their favorable optoelectronic performance and environmental friendliness. However, due to their poor crystallization and easy oxidation, the performance improvement for tin-based perovskite solar cells (TPSCs) is rather challenging. Herein, reductive 3-hydroxytyramine hydrochloride (DACl) with NH2·HCl and phenol groups as co-additives with SnF2 is added into the precursor to modulate perovskite crystallization and inhibit Sn2+ oxidation for high-performance TPSCs. The Lewis base group of NH2 HCl in DACl could bind to perovskite lattices to modulate the crystallization with suppressed defects in the bulk and grain boundary, whereas reductive phenol groups effectively constrain the Sn2+ oxidation. Moreover, the undissociated DACl decreases the supersaturated concentration of tin perovskite solution and creates a pre-nucleation site for rapid nucleation to further regulate crystallization. Consequently, the DACl-derived TPSCs achieve a high power-conversion efficiency (PCE) that reaches up to 11%. More impressively, the device remains at 84% of the initial PCE after full-sun illumination in N2 over 600 h without being encapsulated. This DACl-based synergistic modulation of a lead-free perovskite demonstrates a feasible approach using one molecule with different functional groups to manipulate crystallization, Sn2+ oxidation, and defect reparation of tin perovskite films, providing a critical guideline for constructing high-quality perovskites by multifunctional additives with high photovoltaic performance.

Recent development in electron transport layers for efficient tin-based perovskite solar cells

Hybrid organic-inorganic tin (Sn)-based perovskite materials became a promising choice as an alternative to lead-free perovskite solar cells (PSCs) due to their outstanding optical and electrical properties. But, so far, a power conversion efficiency (PCE) of only 13% has been achieved for Sn-based PSCs. To achieve highly efficient and stable PSCs, not only the properties of the active layer but the charge selective contacts (electron and hole transport layers) should be selected wisely. The interfaces between the perovskite active layer and charge transport layers play an important role in achieving the better performance of PSCs. In the present review, the spotlight is on the recent developments made on the optimization of electron transport layers (ETLs) for the efficient Sn-based hybrid organic-inorganic PSCs. Further, we comprehensively discuss the significance and the impact of the lowest unoccupied molecular orbital level of electron transport material on the charge transport, which additionally affects the photovoltaic performance of the device. In summary, with continuous research on the Sn-based hybrid organic-inorganic perovskite materials as an absorbing layer, conventional ETLs (metal oxides) cannot be used. Thus, the optimum candidate for befitted ETLs must be explored and investigated in detail for efficient PSCs.

Hole-Transport Layer-Free Tin-Based Perovskite Solar Cells: Improving Their Performance from a Simulation Perspective

Perovskite solar cells are in rapid development, however, PCE (photovoltaic conversion efficiency) of HTL-free (Hole Transport Layer free) perovskite solar cells is reported to be low. In this work, we propose a tin-based perovskite solar cell with an ETL (Electron Transport Layer) structure of a novel electron transport layer material. We simulated the device with SCAPS-1D (Solar Cells Capacitance Simulator) and found that all of the absorber layer thickness, band gap, doping concentration, defect density, device working temperature, ETL layer thickness, and doping concentration have different degrees of influence on the device performance. After optimization, (Open Circuit Voltage) is 1.07 V, (Short-circuit Current Density) is 24.25 FF (Filling Factor) is 87.87%, and PCE arrives up to 22.72%. There is a significant performance improvement compared to pre-simulation (initially, is 0.97 V, is 24.21 FF is 69.12%, and PCE is 16.22%). It is shown that when the thickness of the absorber layer is larger than the diffusion length, it leads to harmful photogenerated carrier complexes and increases the diffusion length before reaching the electrode, which affects the carrier transport migration. Defect density bears the brunt of the performance impact, the greater it is the worse the performance, so it should be controlled to a small range. When the operating temperature higher than 300 K, the device performance tends to deteriorate and it is recommended to keep the operating temperature around 300 K. The ETL layer doping concentration and thickness have little influence on performance. Finally, we also analytically simulate and compare several traditional ETL PSCs, and the matching of LUMO (Lowest Unoccupied Molecular Orbital) and absorber energy levels of different ETL materials was found to be different, and the higher the matching is, the more favorable the electron transport and the higher the PCE. This work provides new strategy to design PSCs.

Trapped-Hydrogen-Induced Energy Loss in Tin-Based Hybrid Perovskite Solar Cells

Tin halide perovskites present outstanding optoelectronic properties and great application potential, without the toxicity of lead. Here a systematic first-principles investigation reveals that a high-density defect complex, consisting of a tin vacancy plus a hydrogen molecule (${V}_{\mathrm{Sn}}$--H${}_{2}$), is a highly effective center for nonradiative recombination of electrons and holes in this semiconductor. That would explain the experimentally observed significant nonradiative loss in devices based on formamidinium tin triiodide. Therefore, the passivation of this defect complex is expected to improve the performance of tin-based perovskite solar cells and other optoelectronic devices.

Photoluminescence Intensity Enhancement in Tin Halide Perovskites.

The prevalence of background hole doping in tin halide perovskites usually dominates their recombination dynamics. The addition of excess Sn halide source to the precursor solution is the most frequently used approach to reduce the hole doping and reveals photo-carrier dynamics related to defects activity. This study presents an experimental and theoretical investigation on defects under light irradiation in tin halide perovskites by combining measurements of photoluminescence with first principles computational modeling. It finds that tin perovskite thin films prepared with an excess of Sn halide sources exhibit an enhancement of the photoluminescence intensity over time under continuous excitation in inert atmosphere. The authors propose a model in which light irradiation promotes the annihilation of VSn 2- /Sni 2+ Frenkel pairs, reducing the deep carrier trapping centers associated with such defect and increasing the radiative recombination. Importantly, these observations can be traced in the open-circuit voltage dynamics of tin-based halide perovskite solar cells, implying the relevance of controlling the Sn photochemistry to stabilize tin perovskite devices.

Multidentate Chelation Heals Structural Imperfections for Minimized Recombination Loss in Lead-Free Perovskite Solar Cells.

Tin-based perovskite solar cells (Sn-PSCs) have emerged as promising environmentally viable photovoltaic technologies, but still suffer from severe non-radiative recombination loss due to the presence of abundant deep-level defects in the perovskite film and under-optimized carrier dynamics throughout the device. Herein, we healed the structural imperfections of Sn perovskites in an "inside-out" manner by incorporating a new class of biocompatible chelating agent with multidentate claws, namely, 2-Guanidinoacetic acid (GAA), which passivated a variety of deep-level Sn-related and I-related defects, cooperatively reinforced the passivation efficacy, released the lattice strain, improved the structural toughness, and promoted the carrier transport of Sn perovskites. Encouragingly, an efficiency of 13.7 % with a small voltage deficit of ≈0.47 V has been achieved for the GAA-modified Sn-PSCs. GAA modification also extended the lifespan of Sn-PSCs over 1200 hours.

Mitigating Voc Loss in Tin Perovskite Solar Cells via Simultaneous Suppression of Bulk and Interface Nonradiative Recombination.

Tin-based perovskite solar cells (PSCs) have recently attracted extensive attention as a promising alternative to lead-based counterparts due to their low toxicity and narrow band gap. However, the severe open-circuit voltage (Voc) loss remains one of the most significant obstacles to further improving photovoltaic performance. Herein, we report an effective approach to reducing the Voc loss of tin-based PSCs. We find that introducing ethylammonium bromide (EABr) as an additive into the tin perovskite film can effectively reduce defect density both in the tin perovskite film and at the surface as well as optimize the energy level alignment between the perovskite layer and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) transport material, thereby suppressing nonradiative recombination both in the bulk film and at the interface. Furthermore, it is demonstrated that the Voc loss is gradually mitigated along with increasing storage duration due to the slow passivation effect. As a result, a remarkable Voc of 0.83 V is achieved in the devices optimized with the EABr additive, which shows a significantly improved power conversion efficiency (PCE) of 10.80% and good stability.

Towards high-efficiency tin-based perovskite solar cell by adding co-additives

Towards high-efficiency tin-based perovskite solar cell by adding co-additives

(Invited) Development of High-Performance Tin Perovskite Solar Cells Via a Sequential Two-Step Deposition Approach

The performance of a tin-based perovskite solar cell (PSC) has undergone rapid progress in recent years but most high-performing devices were fabricated according to a traditional one-step method with the key anti-oxidizer or passivator treated as an additive in the perovskite precursor solution. Herein we present a sequential deposition procedure to passivate the surface of a hybrid mixed cationic perovskite with phenylhydrazinium halide (PHX, X = Cl, Br, I and SCN) dissolved in trifluoroethanol (TFE) solvent. TFE plays an important role not only to give PHX sufficient solubility but also to retain the tin-perovskite films intact for an effective surface passivation characterized by SEM, XRD, GIWAX, SIMS, XPS, UPS, c-AMF and TCSPC. A slow surface passivation was observed; the performance of the PHSCN device improved upon increasing the storage period to attain the best efficiency 13.5 % for a current-voltage scan in the forward bias direction. An inverted effect of hysteresis was observed in that the efficiency of the forward scan was greater than of the reverse scan. An ion-migration model due to the effect of PH surface passivation was proposed to account for the observed phenomena. Furthermore, High-performance tin-based PSC have been extensively explored using PEDOT:PSS as a hole-transport material (HTM) layer according to a one-step fabrication method. In the second part of the work we report tin-based PSC using the concept of a self-assembled monolayer (SAM) to modify the ITO surface with deposition in two steps; a traditional one-step method failed to produce a uniform tin perovskite layer on the ITO/SAM surface because of insufficient surface hydrophilicity. Herein we developed a preheating procedure to diminish effectively the amounts of hydroxyl groups and oxygen vacancies on the ITO surface for a uniform SAM to form, which has been characterized with X-ray photoelectron spectra. We found that the ITO substrate preheated at 400 °C gave the best device performance for an efficiency of power conversion attaining 6.5 % with excellent enduring stability in a glove box for ~1900 h without encapsulation. The present work thus provides a new direction for the development of HTM-free lead-free perovskite solar cells for their future up-scale production.

Investigating the band gap on the performance of tin-based perovskite solar cells by device simulation

Investigating the band gap on the performance of tin-based perovskite solar cells by device simulation