Tailoring a dynamic crystalline process during the conversion of lead-halide perovskite layer to achieve high performance solar cells

In this work, organic–inorganic perovskite thin films with a mixed FA0.85MA0.15Pb(Br0.07I0.93)3 composition were prepared using a two-step sequential procedure. The preparation was manipulated by the addition of a small fraction of DMSO to the precursor of the second step. By adjusting the fraction of DMSO, the crystallisation and the PbI2 residue of the perovskite films can be finely controlled. The change in dissolution due to the addition of DMSO altered nucleation dynamics, and molecular intercalation occurred in the initial stage of the reaction, followed by a dissolution–crystallisation process of growth for the crystals. The approach used in this work can be easily controlled and has high reproducibility. The optimised perovskite solar cells prepared here displayed high performance, with the best device achieving a power conversion efficiency of 19.29% without hysteresis.