High performance perovskite solar cells fabricated from porous PbI2-xBrx prepared with mixture solvent pore generation treatment

Abstract

Power conversion efficiencies of perovskite solar cells depend heavily on the uniformity, coverage, grain size, and thickness of the perovskite layer. In this study, hybrid perovskite CH3NH3PbI3-xBrx thin films were fabricated from porous PbI2-xBrx layers prepared with a mixture solvent pore generation treatment process. The mixture solvent is composed of two anti-solvents of PbI2-xBrx to promote its crystallization, one with a low boiling point to accelerate the evaporative removal of the solvents of PbI2-xBrx, dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and the other with a high boiling point to modulate the evaporative removal of DMF and DMSO to achieve a suitably configured porous structure for the PbI2-xBrx layer. With this fast pore generation treatment, uniform porous PbI2-xBrx layers were obtained within minutes, far more efficient than previously reported pore generation processes. The uniform porous PbI2-xBrx layer enabled formation of hybrid perovskite CH3NH3PbI3-xBrx thin films of low PbI2-xBrx residue, good crystallinity, low defect concentrations, and long charge carrier life times. The champion cell, assembled from the optimal hybrid perovskite thin films fabricated from optimized pore generation treatments, exhibited significantly superior power conversion performances of 19.26 mA/cm2 for the short circuit current density, 1.01 V for the open circuit voltage, 0.68 for the fill factor, and 13.16% for the power conversion efficiency, as compared to the average power conversion efficiency of 10.03% for non-porous PbI2-xBrx layer based cells.