Phase formation and local charge transport of lead-free CH3NH3Sn(I1−xBrx)3 (0 ≤ x ≤ 1)perovskite solar cells fabricated by solvent optimization

Abstract

The perovskite layer is the most crucial factor for the high performance tin-based perovskite. Herein, we investigate the effect of solvent on the morphology of perovskite films systematically. Dimethyl sulfoxide (DMSO)has been adopted as a high boiling point combined with the commonly used N,N-dimethylformamide (DMF)to control the rapid nucleation and retarding crystal growth. A pinhole-free MASnI3 perovskite film with dense and large grains is obtained. By optimizing the solvent composition, multiple tin-based mixed iodine and bromine perovskite solar cells (MASn(I1−xBrx)3 0 ≤ x ≤ 1)were fabricated. The best photoconversion cell efficiency was obtained at x = 0.67, which yields to 3.20% compared to the original MASnI3 (1.17%)due to the benefit band level alignment. The conductivity and the stability of the MASn(I1−xBrx)3 perovskite device was carefully studied. © 2019