MnCl2 doping increases phase stability of tin halide perovskites

Abstract

Tin halide perovskite (CH3NH3SnI3) suffers from instability due to the oxidation of tin(II). Doping tin(II) with cations can modify the properties of CH3NH3SnI3 and consequently, its stability. The gains and associated mechanisms differ according to cation. Here, MnCl2 is highlighted as a potential transition metal dopant. Using MnCl2, 2 and 10 mol% Mn doped CH3NH3SnI3 films were synthesized by the one-step method and characterized. Based on X-ray diffraction and micro-Raman measurements, the perovskite structure is formed irrespective of MnCl2 doping. The distribution of Mn was satisfactory as per Energy Dispersive X-ray mapping and chlorine from the precursor is not eliminated. Thus, must be considered when choosing MnCl2 as a dopant. The diffraction patterns of aged samples (24 h in air) indicate partial stabilization with Mn doping. From X-ray photoelectron spectroscopy (XPS) analysis, the stability of tin(II) in 10% Mn was slightly improved, tin vacancies were reduced and SnO2 formation was lowered despite Sn(IV) species being a little higher than the pristine sample. In general, the findings are promising for the development of stable tin perovskite solar cells.