Flattening Grain-Boundary Grooves for Perovskite Solar Cells with High Opto-Mechanical Reliability

Opto-mechanical reliability has emerged as an important criterion for evaluating the performance and commercialization potential of perovskite solar cells (PSCs) due to the mechanical-property mismatch of metal halide perovskites with other device layers. In this work, grain-boundary groove, a rarely discussed film microstructural characteristics, is found to impart significant effects on the opto-mechanical reliability of perovskite-substrate heterointerfaces and thus PSC performance. By pre-burying iso-butylammonium chloride additive in the electron-transport layer, we flattened GB grooves and created an opto-mechanically reliable perovskite heterointerface that resists the photothermal fatigue. The improved mechanical integrity of ETL-perovskite heterointerfaces also benefits the charge transport and chemical stability by facilitating the carrier injection and reducing the moisture or solvent trapping, respectively. Accordingly, we achieved high-performance perovskite solar cells which exhibit efficiency retentions of 94.8% under 440 h damp heat test (85% RH and 85 °C), and 93.0% under 2000 h continuous light soaking.