Slowing hot carriers cooling dynamics via perovskite morphology manipulating enable high-performance perovskite solar cells

Slowing hot carriers (HCs) cooling of lead halide perovskites exhibits great promise for achieving highly efficient perovskite solar cells (PSCs). However, the effect of the quality of perovskite on PSCs performance has not been well studied. Herein, we fabricated high-quality perovskite films by employing an organic small molecule, tris(pentafluorophenyl)borane (TFB) as an additive material. It was found that the perovskite films with TFB become smoother and pinhole-free morphology with increased grain size and reduced trap-state density. More importantly, ultrafast transient absorption spectroscopy results reveal that the high-quality TFB-doped perovskite films can significantly slow down HCs cooling process compared with pristine perovskite film, which is beneficial for prolonging the lifetime of carriers and reducing the charge carrier recombination in the device. Accordingly, the power conversion efficiency (PCE) of CsFAMA-based PSCs doping with TFB is enhanced to 22.56% from the control device (20.22%). Compared with 21.79% efficiency for the control device, a high PCE of 24.09% is obtained in FA-based PSCs treated with TFB. Besides, the unencapsulated TFB-doped device retains 91% of its initial value after storing for 1900 h under ambient conditions (∼45% humidity). These findings provide some insights for understanding HCs’ dynamics for constructing highly efficient PSCs.