Controllable Heavy n-type Behaviours in Inverted Perovskite Solar Cells with Non-Conjugated Passivants

Interfacial issues between the perovskite film and electron transport layer greatly limit the efficiency and stability of inverted (p-i-n) perovskite solar cells (PSCs). Despite organic ammonium passivants have been widely established as interfacial layers, they failed to improve electron extraction. Here, we reported that the heavy n-type characteristics in a low band gap perovskite film could be modulated by incorporating non-conjugated ammonium passivants with strong electron-withdrawing abilities. This resulted in a significant enhancement of electron extraction in the heavily n-type doped perovskite. The passivant-treated PSCs exhibited a power conversion efficiency of 25.74 % with an excellent fill factor of 85.4 % and a high open-circuit voltage of 1.166 V, which are significantly higher than that of the control device. The unencapsulated devices maintained 88 % of their initial PCEs after 1,200 hours at 85 °C.