Defect Passivation in Hybrid Perovskite Solar Cells by Tailoring the Electron Density Distribution in Passivation Molecules.

Commercialization of perovskite solar cells (PSCs) requires developing high-efficiency devices with good stability. Ionic defects existing in the perovskite layer can serve as nonradiative recombination centers to deteriorate the performance of PSCs and can introduce chemical degradation of the perovskite material introducing instability issues. Here, passivation molecules with various electron density distributions (EDD) are employed as an ideal model to reveal the role of EDD on defect passivation in perovskite thin films. Power conversion efficiency (PCE) exceeding 21% with good stability in humid air was obtained for planar PSCs with the 4-aminobenzonitrile (ABN) additive, higher than the reference PSCs with a PCE of 20.22%. The improved stability and performance features are attributed to the efficient passivation for charged defects in perovskites by adding ABN, which guarantees a smaller Urbach energy, longer carrier lifetime, and less traps in the perovskite films.