Although antimony sulfoiodide (SbSI) exhibits very interesting properties including high photoconductivity, ferroelectricity, and piezoelectricity, it is not applied to solar cells. Meanwhile, SbSI is predominantly prepared as a powder using a high‐temperature, high‐pressure system. Herein, the fabrication of solar cells utilizing SbSI as light harvesters is reported for the first time to the best of knowledge. SbSI is prepared by solution processing, followed by annealing under mild temperature conditions by a reaction between antimony trisulfide, which is deposited by chemical bath deposition on a mesoporous TiO2 electrode and antimony triiodide, under air at a low temperature (90 °C) without any external pressure. The solar cells fabricated using SbSI exhibit a power conversion efficiency of 3.05% under standard illumination conditions of 100 mW cm−2.

Tin sulfide (SnS) is one of the most promising solar cell materials, as it is abundant, environment friendly, available at low cost, and offers long‐term stability. However, the highest efficiency of the SnS solar cell reported so far remains at 4.36% even using the expensive atomic layer deposition process. This study reports on the fabrication of SnS solar cells by a solution process that employs rapid thermal treatment for few seconds under Ar gas flow after spin‐coating a precursor solution of SnCl2 and thiourea dissolved in dimethylformamide onto a nanostructured thin TiO2 electrode. The best‐performing cell exhibits power conversion efficiency (PCE) of 3.8% under 1 sun radiation conditions (AM1.5G). Moreover, secondary treatment using SnCl2 results in a significant improvement of 4.8% in PCE, which is one of the highest efficiencies among SnS‐based solar cells, especially with TiO2 electrodes. The thin film properties of SnS after SnCl2 secondary treatment are analyzed using grazing‐incidence wide‐angle X‐ray scattering, and high‐resolution transmittance electron microscopy.

it provides a larger contact area between the TiO 2 and perovskite. Almost all of the best PSC efficiencies published so far have been obtained by using TiO 2 photoelectrodes. [15-18] Moreover, excellent long-term photo-stability has also been reported in PSCs fabricated using TiO 2 electrodes. [19] mp-TiO 2 layers for PSCs can be formed using spin-coating or screen-printing methods with TiO 2 pastes containing organic binders and surfactants (e.g., ethyl cellulose and terpineol), as well as organic solvents. [20,21] Subsequently, the TiO 2 layers require a follow-up such as high-temperature process to burn out the organic components contained in the TiO 2 paste. The biggest advantage of a hightemperature process would be a lowering of the series resistance of the layer, due to the strong contact between the TiO 2 particles and the TCO substrate. Therefore, in terms of efficiency, high-temperature-processed TiO 2 layers are very desirable; nevertheless, their use may be a large limiting factor in the fabrication of PSCs using a low-temperature continuous coating process or substrates based on an organic material (e.g., polyethylene naphthalate (PEN)). [22] Even PEN-based flexible substrates can be problematic, because they can bend if subjected to a heat treatment at 150 °C. Although recent studies have shown that SnO 2 can be used as an ETLs to fabricate PSCs at relatively low temperature, a heat treatment at temperature ≥150 °C is required to reach the best performances. [23,24] Meanwhile, formamidinium lead triiodide (FAPbI 3)-based perovskites are generally heat-treated at 150 °C to obtain an α-phase. If all the processes for high-efficiency PSCs can be conducted at ≈100 °C, their value will be very high in terms of using flexible substrates and facilitating large-area continuous processes. Currently, most high-efficiency PSCs are fabricated using spin coating, a simple and reliable technique that can produce very uniform thin films. However, since it is problematic to apply spin coating in large-area processes, other methods including blade coating, [25] slot die coating, [26] inkjet printing, [27] and spray coating [28] have been actively studied as scalable deposition techniques. Among these, spray coating has been already widely used in several industry fields and offers great advantages for the continuous production of PSC modules with large areas and a reduced material consumption. [29] So far, several groups reported the deposition of perovskite thin films or of entire ETLs, perovskites, and HTLs (required for the fabrication TiO 2 is one of the most efficient and widely used materials for electrontransporting layer (ETLs) in perovskite solar cells (PSCs). The formation of efficient TiO 2 layers is generally carried out at high temperature by baking at a temperature >400 °C or by vacuum deposition (e.g., atomic layer deposition and E-beam). In this study, the preparation of a TiO 2 ETL for PSCs is reported with excellent properties at low temperatures based on the synthesis of a stable TiO 2 colloidal ...

Improving the performance, reproducibility, and stability of Sn-based perovskite solar cells (PSCs) with n-i-p structures is an important challenge. Spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene], a hole transporting material (HTM) with n-i-p structure, requires the oxygen exposure after addition of Li-TFSI [Lithium bis(trifluoromethanesulfonyl) imide] as a dopant to increase the hole concentration. In Sn-based PSC, Sn 2+ is easily oxidized to Sn 4+ under such a condition, resulting in a sharp decrease in efficiency. Herein, a formamidinium tin triiodide (FASnI 3 )-based PSCs fabricated using DPI-TPFB [4-Isopropyl-4′-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate] instead of Li-TFSI are reported as a dopant in Spiro-OMeTAD. The DPI-TPFB enables the fabrication of PSCs with an efficiency of up to 10.9%, the highest among FASnI 3 -based PSCs with n-i-p structures. Moreover, ≈80% of the initial efficiency is maintained even after 1,597 h under maximum power point tracking conditions. In particular, the encapsulated device does not show any decrease in efficiency even after holding for 50 h in the 85 °C/85% RH condition. The high efficiency and excellent stability of PSCs prepared by doping with DPI-TPFB are attributed to not only increasing electrical conductivity by acting as a Lewis acid, but also stabilizing Sn 2+ through coordination with Sn 2+ on the surface of FASnI 3 .

Metal halide perovskite solar cells (PSCs) have been considered to be one of the most promising next‐generation energy harvesters over the past decades due to remarkably rapid improvement of power conversion efficiency in photovoltaics. However, energy harvesters based on the solar energy source have an intrinsic environment limitation for indoor applications. A feasible solution to the limitation is to add non‐solar energy harvesting functions to the solar energy harvesters. Here, the piezoelectric properties of two types of metal halide PSCs are investigated, the 3D only and the 3D/2D structure, showing PCEs of 21.3% and 23.2%, respectively. Piezo‐response force microscopy and synchrotron‐based X‐ray diffraction demonstrate that both types of PSC sample have piezoelectricity. Remarkably, the 3D/2D structure has considerably higher piezoelectric amplitude than the 3D‐only. The deep level transient spectroscopy results reveal that the enhancement in the piezoelectricity of the 3D/2D structure originates from PbBr defects. This study unravels the role of defects in the piezoelectricity of metal halide PSCs and provides a direction to develop the multi‐function energy harvesters based on the PSCs.