Controllable perovskite crystallization via potassium pretreatment toward high-performance solar cells

High-photoelectric performance and long-term stability of perovskite solar cells (PSCs) are closely related to the crystallinity and morphology of organic-inorganic halide perovskite films. However, interfaces and grain boundary defects of perovskite films could degrade the quality of perovskite films. In this work, potassium nitrate (KNO3) was taken to pretreat the compact TiO2 layer by a simple spin-coating method, which can simultaneously passivate both the electron transport layer (ETL)/perovskite interface defects and grain boundaries defects in perovskite films. Accordingly, the crystallinity and absorption intensity of the perovskite films were improved, which also enlarged the grain size, prolonged carrier lifetimes, and reduced the defect density. Therefore, an enhancement of short-circuit current density ranges from 22.56 to 24.00 mA cm(-2) and a corresponding power conversion efficiency increases from 16.74% to 19.26%. PSCs also show that improved operational stability was 40%-65% with only 20% power conversion efficiency loss after 320 h under the relative humidity. The ETL modified by KNO3 reported herein provided a new approach of defect passivation with high-performance PSCs.