A Co‐Deposition Approach for Self‐Assembled Molecules and Perovskites Achieving > 20% Efficiency in Wide‐Bandgap Perovskite Solar Cells

Co‐deposited strategy of self‐assembled molecule (SAM) and perovskite could simplify the fabrication process as well as achieving the high‐performance solar cells. However, the correlative mechanism between molecular structures, film crystallization kinetics, and device properties is not clearly identified. Herein, referring to representative carbazole‐phosphoric acid molecules, we introduced a π‐conjugation extended carbazole of (2‐(12‐phenylindolo[2,3‐a]carbazol‐11(12H)‐yl)ethyl)phosphonic acid (named by SAM‐XS22). The XS22 additive with larger steric hindrance could improve the perovskite crystallinity as well as the reduced peak intensity of excess PbI 2 and accelerate the interfacial carrier extraction/transfer due to the heterogeneous SAM distribution within bulk film. As a result, we achieved the champion power conversion efficiency of ∼20.72% for 1.78‐eV FA 0.83 Cs 0.17 Pb(I 0.6 Br 0.4 ) 3 wide‐bandgap perovskite solar cells, which can also remain > 90% retention over 600 hours of maximum‐power‐point tracking.