Efficient carrier utilization induced by conductive polypyrrole additives in organic-inorganic halide perovskite solar cells

•Polypyrrole additives increase the PCE of mixed halide perovskite solar cells.•Morphological smoothness leads to lower charge carrier recombination.•Enhanced transport of the charge carriers into electron and hole transfer layers. The morphology of the perovskite layer, the effective extraction of the charge carriers, and their transport are the main factors determining the power conversion efficiency (PCE) of the perovskite solar cells (PSCs). In this work, we demonstrated that the geometric and electronic structures of the PSCs could be modified by using a conductive polymer additive in the lead (Pb) halide layer prepared by a two-step deposition method. Polypyrrole (PPy) as a conductive polymer is used in the perovskite layers which could increase the PCE of CH3NH3PbI3-xClx mixed-halide PSCs. By adding an optimized amount of PPy, PCE has been raised from 10.4 to 13.2%. PPy acts as a conductive channel facilitating the extraction of the charge carriers and easing their transport in the perovskite layer. The crystallization is also affected by PPy which is advantageous to form smooth perovskite layers with fewer voids.