Non-toxic solvent-processed tin-halide perovskite solar cells via weak coordination

Abstract

Tin-halide perovskite solar cells (TPSCs) have aroused unprecedented attention owing to their low toxicity, high carrier mobility, and high theoretical efficiency. However, the solvents used in fabricating these devices are always toxic. Herein, we demonstrated a non-toxic solvent system of N,N-diethylformamide (DEF) and dimethyl sulfoxide (DMSO) to dissolve the perovskite raw materials. The coordination ability with Sn²⁺, colloidal chemistry, crystallization process, carrier transport, and recombination dynamics were systematically studied. Our results revealed that DEF has a slightly weaker coordination ability with Sn²⁺, rendering the formation of smaller colloids in the precursor solution. Smoother perovskite film with a larger grain size was obtained due to the decreased nucleation sites and retarded crystal growth. Moreover, the as-fabricated TPSC device with DEF showed enhanced carrier mobility and suppressed non-radiative recombination with a lower defect density. As a result, the DEF device achieved a comparable power conversion efficiency to the device fabricated with the toxic N,N-diethylformamide (DMF) solvent. This work sheds light on green solvent selection for the large-scale fabrication of TPSCs.