Tin Halide Perovskites Research Articles

Efficient and Stable Mesoporous CsSnI3 Perovskite Solar Cells via Imidazolium‐Based Ionic Liquid Additive

Inorganic tin halide perovskite compound with its eco‐friendly property has attracted tremendous attention of researchers in the field of lead‐free perovskite solar cells. However, the trap‐assisted nonradiative recombination caused by deep‐level defects originating from surface undercoordinated Sn2+ cations significantly deteriorates the CsSnI3 device's performance. Herein, adding low concentrations of an ionic liquid 1‐ethyl‐3‐methylimidazolium acetate (EMIMAc) shows promise in controlling deep‐level defects in CsSnI3 perovskites. Both experimental observation and theoretical simulation reveal that EMIMAc can have strong electrostatic attraction and coordination interaction with the surface undercoordinated Sn2+ through the lone electron pairs of carboxyl functional groups and the donated π electrons from electron‐rich imidazole moieties, leading to a reduced deep‐level defect density and a restrained nonradiative recombination. Consequently, the processed CsSnI3 perovskite solar cells based on a printable fluorine‐doped tin oxide/compact‐TiO2/mesoporous‐TiO2/Al2O3/NiO/carbon framework achieve a power conversion efficiency as high as 8.54%, which is the champion efficiency among all the reported CsSnI3 mesoporous perovskite solar cells up to now. In addition, the unencapsulated devices have shown an impressive long‐term stability with only ≈6% efficiency degradation after over 2000 h aging under nitrogen atmosphere.

Fast and Highly Sensitive Photodetectors Based on Pb‐Free Sn‐Based Perovskite with Additive Engineering

AbstractOrganic–inorganic halide perovskites have been widely investigated for the fabrication of photodetectors because of their excellent optoelectronic properties. However, the toxicity of Pb‐based perovskites and the lack of manufacturing technology in air limits the commercialization of perovskite‐based photodetectors. Tin halide perovskite (THP) is a promising candidate to replace Pb‐based perovskites due to its low toxicity and potential commercialization. However, THP suffers poor stability in air because Sn2+ is easily oxidized to Sn4+. This “self‐doping” effect not only degrades device performance rapidly, but also makes it difficult to fabricate THP‐based devices in air. Here, Pb‐free Sn‐based 2D perovskite PEA2SnI4 films with tin fluoride (SnF2) additive are prepared in air using a nitrogen quenching hot casting method. The photodetectors with an optimal SnF2 concentration of 20% exhibit a fast response speed of 0.56 ms and an excellent specific detectivity of 6.32 × 1013 Jones, the best combination of THP‐based photodetectors reported hitherto. The SnF2 additive is found to suppress the formation of Sn vacancies and improve the crystallinity of PEA2SnI4 films. The work provides an air‐processing technology of Pb‐free perovskite, which is easy to commercialize, and SnF2 additive engineering offering an effective way to demonstrate high performance photodetectors and image recognition applications.

Highly symmetric Lewis base coordinated with Sn2+ for reducing voltage loss and retarding oxidation in tin-halide perovskite solar cells

The power conversion efficiency (PCE) of tin perovskite solar cells (TPSCs) has made significant breakthroughs recently, making them the most promising eco-friendly perovskite solar cells. However, the uncontrollable crystallization process and the easy oxidation of Sn2+ limit the achievable open-circuit voltage (Voc) and PCE. Herein, a highly symmetric Lewis base small molecule of melamine was introduced into perovskite precursor solution to coordinate with Sn2+, thus effectively modulate the crystallization process of tin perovskite and the oxidation degree of Sn2+. Meanwhile, the introduction of melamine greatly reduced the defect-induced non-radiative recombination in tin perovskites. As a result, the target TPSCs achieved a PCE of 10.3 % and excellent stability, which maintained 85 % of its initial PCE after aging in N2 glove box for 1300 h and 78 % in air for 30 h. Thus, our work provides a feasible strategy to modulate the crystallization process of tin perovskite for reducing the Voc loss in TPSCs.

Sn-Based Perovskite Halides for Electronic Devices.

Because of its less toxicity and electronic structure analogous to that of lead, tin halide perovskite (THP) is currently one of the most favorable candidates as an active layer for optoelectronic and electric devices such as solar cells, photodiodes, and field-effect transistors (FETs). Promising photovoltaics and FETs performances have been recently demonstrated because of their desirable electrical and optical properties. Nevertheless, THP's easy oxidation from Sn2+ to Sn4+ , easy formation of tin vacancy, uncontrollable film morphology and crystallinity, and interface instability severely impede its widespread application. This review paper aims to provide a basic understanding of THP as a semiconductor by highlighting the physical structure, energy band structure, electrical properties, and doping mechanisms. Additionally, the key chemical instability issues of THPs are discussed, which are identified as the potential bottleneck for further device development. Based on the understanding of the THPs properties, the key recent progress of THP-based solar cells and FETs is briefly discussed. To conclude, current challenges and perspective opportunities are highlighted.

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.

Unveiling the Role of the Metal Oxide/Sn Perovskite Interface Leading to Low Efficiency of Sn-Perovskite Solar Cells but Providing High Thermoelectric Properties

Tin halide perovskites (THPs) have appealing optoelectronic properties similar to lead halide perovskites (LHPs). However, THPs coated on metal oxide electrodes in normal-structure perovskite solar cells exhibit poor diode rectification, resulting in poor efficiency. This poor photoelectric performance in n–i–p-based THP solar cells is in contrast with LHP solar cells. We report that this deficient performance of THP solar cells is triggered by the defect states of the metal oxide layer. The defect states of the metal oxide can trap the electrons from the THP, leading to the prompt formation of Sn(IV), which will increase the carrier density and lead to poor photoelectric performance. This observation was supported by the ultraviolet-photoelectron spectroscopic measurements of inorganic thin films Al2O3, SnO2, TiO2, ZnO, and ZrO2. However, this self-doping phenomenon resulting in the increase in carrier density can be applied to thermoelectric studies. Using CsSnI3/ZrO2 nanocomposites as thermoelectric active layers, we report a power factor of 186.58 μW/mK2 measured at room temperature, which is better than the 148.61 μW/mK2 of the original CsSnI3 thin film.

Lewis base manipulated crystallization for efficient tin halide perovskite solar cells

Tin halide perovskite is the most prospective lead-free perovskite material due to its close to ideal band gap and similar optoelectronic properties to the lead counterparts. Nevertheless, the lack of a regulated crystallization process leads to considerable defects and pinholes in those tin perovskite films, further deteriorating the achievable power conversion efficiency (PCE) for related solar cells. Herein, we employed a facile Lewis base thiourea (TU) into the perovskite precursor to form a SnI2-TU as an intermediate adduct to guide the crystallization kinetics, where the interaction between SnI2 and TU was detected by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements, respectively. Improving the perovskite morphology with TU contributed to significant suppression of the non-radiative recombination and fast charge extraction through carrier dynamics analysis. These benefits delivered a remarkable PCE of over 10% in inverted tin perovskite solar cells, which was 24% higher than the original device. The unencapsulated device with TU retained 90% of the initial efficiency after over 1600 h in N2 atmosphere.

Enhanced piezoelectricity in lead-free halide perovskite nanocomposite for self-powered wireless electronics

Lately, lead-free flexible piezoelectric nanogenerators (PENGs) have drawn much attention because of the threat posed by lead (Pb)-based piezoelectric materials to the environment. Here, we reported an organic-inorganic hybrid perovskites (OIHP) PENG, which is a combination of lead-free formamidinium tin (Sn) halide perovskite (CH(NH2)2SnBr3 (FASnBr3)) nanoparticles (NPs) and polydimethylsiloxane (PDMS) polymer matrix. By using piezoelectric force microscopy (PFM) measurements, we unveil the excellent piezoelectric properties of the FASnBr3 NPs with a high piezoelectric charge coefficient (d33) of ~ 50 pm/V. Due to the outstanding flexibility and uniform distribution properties, the device demonstrated a maximum piezoelectric peak to peak output voltage of 94.5 Vp-p, peak to peak current of 19.1 μAp-p, and output power density of 18.95 μW/cm2 with a tiny force of 4.2 N; these characteristics substantially outperform a number of the state-of-the-art halide perovskite based PENGs (Table S1). Given their high electromechanical energy conversion efficiency, the electrical energy produced from the PENGs was used to power a Bluetooth-capable system on chip (SoC) to build an entirely self-powered radio frequency (RF) communication system. For the first time, we established a self-powered RF wireless communication between nanogenerator and smart electronic devices which is solely based on a lead-free PENG. It is anticipated that the fabricated FASnBr3 @PDMS nanocomposite PENG not only possesses outstanding performance and reliability but also serves as a stepping-stone towards achieving self-powered Internet of Things (IoT) devices built using environment-friendly perovskite piezoelectric materials.

Stable Lead‐Free Tin Halide Perovskite with Operational Stability >1200 h by Suppressing Tin(II) Oxidation

AbstractSn‐based perovskites are the most promising alternative materials for Pb‐based perovskites to address the toxicity problem of lead. However, the development of SnII‐based perovskites has been hindered by their extreme instability. Here, we synthesized efficient and stable lead‐free Cs4SnBr6 perovskite by using SnF2 as tin source instead of easily oxidized SnBr2. The SnF2 configures a fluorine‐rich environment, which can not only suppress the oxidation of Sn2+ in the synthesis, but also construct chemically stable Sn−F coordination to hinder the electron transfer from Sn2+ to oxygen within the long‐term operation process. The SnF2‐derived Cs4SnBr6 perovskite shows a high photoluminescence quantum yield of 62.8 %, and excellent stability against oxygen, moisture, and light radiation for 1200 h, representing one of the most stable lead‐free perovskites. The results pave a new pathway to enhance the optical properties and stability of lead‐free perovskite for high‐performance light emitters.

Stable Lead-Free Tin Halide Perovskite with Operational Stability >1200 h by Suppressing Tin(II) Oxidation.

Sn-based perovskites are the most promising alternative materials for Pb-based perovskites to address the toxicity problem of lead. However, the development of SnII -based perovskites has been hindered by their extreme instability. Here, we synthesized efficient and stable lead-free Cs4 SnBr6 perovskite by using SnF2 as tin source instead of easily oxidized SnBr2 . The SnF2 configures a fluorine-rich environment, which can not only suppress the oxidation of Sn2+ in the synthesis, but also construct chemically stable Sn-F coordination to hinder the electron transfer from Sn2+ to oxygen within the long-term operation process. The SnF2 -derived Cs4 SnBr6 perovskite shows a high photoluminescence quantum yield of 62.8 %, and excellent stability against oxygen, moisture, and light radiation for 1200 h, representing one of the most stable lead-free perovskites. The results pave a new pathway to enhance the optical properties and stability of lead-free perovskite for high-performance light emitters.

Understanding the Limitations of Charge Transporting Layers in Mixed Lead–Tin Halide Perovskite Solar Cells

Understanding the Limitations of Charge Transporting Layers in Mixed Lead–Tin Halide Perovskite Solar Cells

High-performance flexible lead-free perovskite solar cells based on tin-halide perovskite films doped by reductant metal halide

The lead-free perovskite solar cell could break the limit of the toxicity of lead. However, the oxidation of Sn2+ limits the performance of Sn-based perovskite solar cells. Here, we replied the reductant metal halide as reducing agent in perovskite film, efficiently suppressing the oxidation of Sn2+. Based on the high quality FA0.8MA0.2SnI2.8Br0.2 film with 0.10 M FeCl2, a flexible lead-free perovskite solar cell device was obtained with PCE of 5.24%, and it could maintain 50% of initial PCE after half a year of storage in the N2 glovebox.

Reducing the interfacial voltage loss in tin halides perovskite solar cells

Tremendous attention has been given to tin halide perovskite solar cells (TPSCs) due to the lower toxicity and similar electronic configuration compared with the lead perovskites. Nevertheless, on account of the intrinsic low bandgap, high defect density and surface/interface non-radiative recombination, the open-circuit voltage loss (Vloss) of TPSCs is comparatively large in all semiconductor solar cells. Herein, a hydrophobic bulky molecule of 3-(trifluoromethyl) phenethylamine hydroiodide (CF3PEAI) was utilized to passivate the lead-free perovskite surface by post-deposition treatment. The Vloss of the corresponding PSC devices was significantly reduced to afford a high open-circuit voltage (Voc) up to 0.73 V with a power conversion efficiency (PCE) of 10.35% in conjunction with the broadly utilized (6,6)-Phenyl C61 butyric acid methyl ester (PC61BM). Additionally, the CF3PEAI interlayer expressively suppressed the interfacial non-radiative recombination accompanying with extending photoexcited carrier lifetime. The formation of oriented 2D Sn-based perovskite could also facilitate the vertical charge-carrier transportation and improve the efficiency of Sn-based PSCs. The density of defect states and the amount of mid-gap states required to be filled were both dramatically reduced. Meanwhile, the surface reconstruction can effectively relax the tensile surface strain with the phenethyl ammonium iodide ligands. Therefore, this surface passivation strategy contributes to the development of high-quality lead-free perovskite film with low internal defects and residual stress.

Improving the efficiency of solar cells based on CsSn0.5Ge0.5I3 perovskite by using ZnO nanorods

Subject of study. Environmentally friendly tin and germanium-based halide perovskite materials are promising candidates attracting more attention as lead-free halide perovskite solar cells. However, the limited power conversion efficiency of these perovskites is an important issue in the solar cells field. Therefore, in the present study, a different lead-free perovskite was used to reach higher power conversion efficiency. Devices with an indium tin oxide/electron transport layer/perovskite/hole transport layer/Ag structure but different absorber layers were simulated. Simulation was done using the Solar Cell Capacitance Simulator (SCAPS-1D) to investigate the photovoltaic performance of solar cells with CsGeI3 and CsSnI3 perovskites as the absorber layer. Method. Simulation was done by using the SCAPS software, which is a one-dimensional solar cell simulation platform developed at the Department of Electronics and Information Systems of the University of Gent, Belgium. Main results. The effect of the absorber layer thickness was investigated, and a maximum power conversion efficiency of 10.51% was obtained for 1000 nm thick CsGeI3, while the maximum value of 12.83% was obtained for 400 nm thick CsGeI3. Then, to further increase the efficiency, devices with an alternative lead-free CsSn0.5Ge0.5I3 perovskite including a planar ZnO layer and ZnO nanorod arrays as electron transport layers was used in the simulation, and the thickness of the absorber layer was optimized for both devices. For the maximum power conversion efficiency of the devices, the values of 17.56% and 22.61% were achieved for devices with a ZnO layer and ZnO nanorods, respectively. It is noted that the simulation results of this study could provide a perspective towards fabricating an environmentally friendly perovskite-based solar cell. Practical significance. The main significance of the present work is obtaining a significant power conversion efficiency of 22.61% for a device based on environmentally friendly perovskite. Similar work was done in 2021 by M. Azadinia et al. [Mater. Today Energy20, 100647 (2021)10.1016/j.mtener.2021.100647], in which a comparable power conversion efficiency of 26.9% was reported for a device with CsSn1−xGexI3 perovskite.

High Open Circuit Voltage Over 1V Achieved in Tin-Based Perovskite Solar Cells with a 2D/3D Vertical Heterojunction.

2D–3D mixed tin halide perovskites are outstanding candidate materials for lead‐free perovskite solar cells (PSCs) due to their improved stability and decreased trap density in comparison with their pure 3D counterparts. However, the mixture of multiple phases may lead to poor charge transfer across the films and limit the device efficiency. Here, a stacked quasi‐2D (down)–3D (top) double‐layered structure in perovskite films prepared via vacuum treatment is demonstrated, which can result in a planar bilayer heterojunction. In addition, it is found that the introduction of guanidinium thiocyanate (GuaSCN) additive can improve the crystallinity and carrier mobility in the 2D perovskite layer and passivate defects in the whole film, leading to a long carrier lifetime (>140 ns) in photoluminescence measurements. As a result, the PSCs show a high open circuit voltage (VOC) up to 1.01 V with a voltage loss of only 0.39 V, which represents the record values ever reported for tin‐based PSCs. The champion device exhibits a power conversion efficiency (PCE) of 13.79% with decent stability, retaining 90% of the initial PCE for 1200 h storage in N2‐filled glovebox.

Optical absorption and stability enhancement in mixed lead, tin, and germanium hybrid halide perovskites for photovoltaic applications

Hybrid halide perovskite (HHP) materials present flexible version of next-generation solar cells and among these, Methyl ammonia lead iodide, i.e., CH3NH3PbI3 (MAPbI3), dominated the research field owing to its excellent photovoltaic properties, but its commercial deployment was halted due to the presence of toxic Pb. Mixed cation and anion strategies can play a significant role in improving structural stability and reducing toxicity. Partial or full replacement of Pb with congener but non-toxic elements such as Sn and Ge can facilitate the large uptake of HHP solar cells. In this work by first-principles calculations, we explore the potential alternatives to MAPbI3 by investigating the structural, electronic and optical properties of MAPb1-x-ySnxGeyI3 [(x, y) = (0, 0.5), (0.25, 0.25) (0.5, 0)]. The present report indicates that via Ge and Sn-doping in MAPbI3, the bandgap can be tuned from 1.16 eV to 0.77 eV. Meanwhile, in the Sn/Ge/Sn–Ge doped MAPbI3, the optical absorption coefficients get enhanced in the visible region and in the regions as far as mid-infrared, making them better alternatives to toxic MAPbI3 for photovoltaic applications. Moreover, owing to the outstanding photovoltaic characteristics, MAPb0.50Sn0.25Ge0.25I3 is proposed as an absorber layer material for the efficient perovskite solar cell modules.

Effect of Electronic Doping and Traps on Carrier Dynamics in Tin Halide Perovskites

Effect of Electronic Doping and Traps on Carrier Dynamics in Tin Halide Perovskites

Relationship between Carrier Density and Precursor Solution Stirring for Lead-Free Tin Halide Perovskite Solar Cells Performance

Relationship between Carrier Density and Precursor Solution Stirring for Lead-Free Tin Halide Perovskite Solar Cells Performance

Biuret Induced Tin-Anchoring and Crystallization-Regulating for Efficient Lead-Free Tin Halide Perovskite Light-Emitting Diodes.

Lead-free perovskite emitters, particularly 2D tin (Sn) halide perovskites, have attracted considerable academic attention in recent years. However, the problems of Sn oxidation and rapid crystallization lead to an inferior perovskite morphology with high trap states, thus limiting the luminous efficiency of Sn halide perovskite light-emitting diodes (PeLEDs). In this study, the authors establish an approach by introducing an organic additive, 2-imidodicarbonic diamide (biuret), to address the issues of Sn oxidation and fast crystallization. The unique symmetrical carbonyl groups in the biuret robustly interact with the Sn-I framework, providing a strong Sn-anchoring effect. Consequently, it also suppresses the easy oxidation of Sn2+ , regulating the crystallization process simultaneously. Density functional theory (DFT) calculations also confirmed the robust interaction between the biuret and the 2D Sn halide perovskite. Furthermore, the authors demonstrate efficient PeLEDs with saturated red emission at 637nm, a maximum luminance (Lmax ) of 418cd m-2 , a maximum external quantum efficiency (EQEmax ) of 1.37%, and a half-life (T50 ) of 288 s. This work provides insights on the microcosmic chemical interaction between organics and 2D Sn halide perovskites, advancing the development of efficient lead-free PeLEDs.