Solvents for Processing Stable Tin Halide Perovskites

Tin
is one of the most promising alternatives to lead to make lead-free
halide perovskites for optoelectronics. However, the stability of
tin-based perovskites is hindered by the oxidation of Sn­(II) to Sn­(IV).
Recent works established that dimethyl sulfoxide, which is one of
the best-performing solvents for processing perovskite, is the primary
source of tin oxidation. The quest for a stable solvent could be a
game-changer in the stability of tin-based perovskites. Starting from
a database of over 2000 solvents, we identified a series of 12 new
solvents suitable for the processing of formamidinium tin iodide perovskite
(FASnI3) by investigating (1) the solubility of the precursor chemicals
FAI and SnI2, (2) the thermal stability of the precursor
solution, and (3) the possibility of forming perovskite. Finally,
we demonstrate a new solvent system to produce solar cells outperforming
those based on DMSO. Our work provides guidelines for further identification
of new solvents or solvent mixtures for preparing stable tin-based
perovskites.