Soldering Grain Boundaries Yields Inverted Perovskite Solar Cells with Enhanced Open‐Circuit Voltages

Abstract

Grain boundaries (GBs) are one of the major sources of defects in a polycrystalline perovskite solar cell and can greatly increase the rate of charge carrier recombination. In the push to optimize the efficiency of perovskite solar cells, it is therefore extremely important to maximize the grain size and minimize the number of GBs. In the present work, the number of GBs is effectively reduced by introducing a suitable number of formamidinium and chloride ions into the methylammonium lead iodide (MAPbI3) absorber layer. Inverted perovskite solar cells, using NiOx nanocrystals as the low‐temperature‐fabricated hole transport layer, are prepared; the champion cell has an efficiency of 19.6%. This work demonstrates a simple method of minimizing the number of grain boundaries, which is critical to the future development of this technology.