Tin-based perovskite solar cells offer a less toxic alternative to their lead-based counterparts. Despite their promising optoelectronic properties, their performances still lag behind, with the highest power conversion efficiencies reaching around 15%. This efficiency limitation arises primarily from electronic defects leading to self-p-doping and stereochemical activity of the Sn(II) ion, which distorts the atomic arrangement in the material. In this study, we investigate the effect of strontium doping in tin-based perovskite on the distortion of the material’s structure and its optoelectronic properties. Using a combination of Density Functional Theory calculations and experiments, we demonstrate that strontium doping reduces p-doping and structural strain. This approach improves the efficiency from 6.3% in undoped devices to 7.5% in doped devices without relying on dimethyl sulfoxide, a harmful solvent for tin-based perovskites. This method could enable precise control of tin off-centering and self-p-doping, advancing the development of efficient and stable tin perovskite solar cells.

Indoor photovoltaic (IPV) technology has emerged as an effective strategy to sustainably power batteryless Internet of Things (IoT) devices. Though tin perovskite solar cells offer competitive IPV performance, their effectiveness is often compromised by Sn²⁺ oxidation, particularly when processed with dimethyl sulfoxide (DMSO) solvent. This work explored the IPV performance of DMSO-free tin perovskites FASnI_3–x Br _x by tuning the halide composition. Notably, X-ray photoelectron spectroscopy confirms no traces of Sn⁴⁺, highlighting the critical role of eliminating DMSO. Under 1000 lx indoor illumination, the power conversion efficiency (PCE) increases with Br content, reaching a maximum of 11.1% for FASnI₂Br without introducing any reducing agent. Remarkably, after six months of storage, it exhibited an impressive indoor PCE of 11.9%, demonstrating the effectiveness of the DMSO-free processing route for the intrinsic stability of the tin perovskite. These findings provide crucial insights for developing high-performance, lead-free perovskite materials for sustainable energy applications and IoT devices.

Hybrid halide perovskites are among the most promising candidates for next‐generation photovoltaics. The most investigated perovskite solar cells are lead based, which poses environmental concerns, making finding sustainable alternatives a pressing issue. Tin‐based halide perovskites are attracting interest as an alternative. However, their application in photovoltaics is hindered by the high concentration of defects and sensitivity to oxidation, compromising their performance and stability. Herein, perfluoroarene organic cations, namely 2‐(perfluorophenyl)methylammonium (F‐BNA) and 1,4‐(perfluorophenyl)dimethylammonium (F‐PDMA), are applied to form layered (2D) Ruddlesden–Popper and Dion–Jacobson tin‐based perovskites, respectively. Following a detailed structural and optoelectronic characterization, the perfluoroarenes are applied to formamidinium (FA)‐based FASnI ₃ perovskite solar cells and an effective solvent is identified for their processing, 2‐pentanol. While F‐PDMA forms a 2D/3D heterostructure, F‐BNA remains assembled as a molecular interlayer, demonstrating higher photovoltaic performance with limited operational stability. This challenges the conventional role of mixed‐dimensional heterostructures in tin perovskite photovoltaics and opens new perspectives for advanced material design and device engineering.