Methodologies toward Highly Efficient Perovskite Solar Cells

A perovskite solar cell (PSC) employing an organic–inorganic lead halide perovskite light harvester, seeded in 2009 with power conversion efficiency (PCE) of 3.8% and grown in 2011 with PCE of 6.5% in dye-sensitized solar cell structure, has received great attention since the breakthrough reports ≈10% efficient solid-state PCSs demonstrating 500 h stability. Developments of device layout and high-quality perovskite film eventually lead to a PCE over 22%. As of October 31, 2017, the highest PCE of 22.7% is listed in an efficiency chart provided by NREL. In this Review, the methodologies to obtain highly efficient PSCs are described in detail. In order to achieve a PCE of over 20% reproducibly, key technologies are disclosed from the viewpoint of precursor solution chemistry, processing for defect-free perovskite films, and passivation of grain boundaries. Understanding chemical species in precursor solution, crystal growth kinetics, light–matter interaction, and controlling defects is expected to give important insights into not only reproducible production of high PCE over 20% but also further enhancement of the PCE of PCSs.