High efficiency planar Sn–Pb binary perovskite solar cells: controlled growth of large grains via a one-step solution fabrication process

One-step solution fabrication of high-performance Sn-including perovskite solar cells (PSCs) is very challenging due to the rapid crystallization of the Sn-based perovskite layer, leading to a poor film morphology and low surface coverage. In this work, a well-controlled one-step method, assisted by a multi-step solvent treatment, is developed for the growth of a high-quality CH 3 NH 3 Pb (1−x) Sn x I 3 (0 ≤ x ≤ 1) perovskite film on a planar PEDOT:PSS substrate. The CH 3 NH 3 Sn 0.25 Pb 0.75 I 3 perovskite films consisting of densely packed and uniformly distributed large crystal grains were obtained using sec -butyl alcohol solvent engineering and N , N -dimethylformamide solvent annealing under an N 2 atmosphere. The CH 3 NH 3 Sn 0.25 Pb 0.75 I 3 -based PSCs with a maximum power conversion efficiency (PCE) of 12.08% and an average PCE of 11.01% were obtained. The PSCs also exhibit excellent performance reproducibility, good air stability and weak hysteresis behavior. The enhancement in the performance of the PSCs is attributed to the well-crystallized CH 3 NH 3 Sn 0.25 Pb 0.75 I 3 film, resulting in simultaneous improvement in charge–carrier transport properties and reduction in charge–carrier recombination, a very promising approach to obtain high performance Sn-including perovskite solar cells.