Solvent additives coordination effect on PbI2 precursor and high-performance perovskite solar cells

Abstract

Organic-inorganic hybrid perovskite solar cells, which can be fabricated via a solution process technology, have attracted much attention regarding high efficiency and low fabrication cost. In particular, the formation of high-quality pin-hole-free perovskite layers with large grains would be a key to the high power conversion efficiency (PCE) of solar cells. Here, we report the effect of solvent additives on perovskite formation regarding Gutmann donor number (DN) in PbI2 precursor solution through the two-step spin-coating process. Among the various solvent additives, dimethyl sulfide (DMS) has a high DN of 23.5 kcal·mol-1. The PbI2 precursor solution with DMS leads to the formation of perovskite thin film with a large grain and excellent electrical properties. The power conversion efficiency of our mixture of perovskite layers (FA0.7MA0.3)Pb(I0.7Br0.1Cl0.2)3 based solar cell achieves a maximum PCE of 21.2% under AM 1.5G illumination. Our work suggests enormous potential for significant performance improvement of perovskite solar cells via solvent engineering.