CsPbBr3 nanocrystals as electron and ion "Reservoirs" to induce energy transfer and grain reconstruction for efficient carbon-based inorganic perovskite solar cells.

[Display omitted] A perovskite nanocrystal-molecular hybrid is fabricated to heal the defective perovskite surface. Arising from the role of perovskite nanocrystals as electron and ion reservoirs simultaneously, the soft perovskite lattice is well solidified, significantly improving the efficiency and stability of all-inorganic CsPbI x Br 3-x perovskite solar cells. • An organic molecule bound CsPbBr 3 nanocrystal is fabricated to passivate the perovskite surface. • The passivation ability is enhanced owing to the energy transfer between nanocrystal and organic molecule. • A champion efficiency up to 11.60% for all-inorganic CsPbIBr 2 cell and 14.44% for CsPbI 2 Br cell is achieved. • The unencapsulated device shows excellent tolerance under harsh conditions. Electron cloud density around the functional group of Lewis-base molecule (passivator) highly determines the interaction strength with undercoordinated Pb2+ in perovskite film. With the aim to maximize this scenario, herein, we fabricate a thermally-activated delayed fluorescence molecule (3,4,5,6-tetrakis(3,6-diphenylcarbazol-9-yl)-1,2-dicyanobenzene, 4CzPN-Ph) bound CsPbBr 3 nanocrystal (NC) to heal the defective perovskite surface. Because of the suitable energy alignment, there is a Förster or Dexter triplet energy transfer process from CsPbBr 3 NC donor to 4CzPN-Ph acceptor under light irradiation, leading to the increased electron density within 4CzPN-Ph molecule and thus the enhanced passivation ability. Together with the formation of compositional gradient layer owing to the halide exchange reaction with CsPbBr 3 NCs, the stable perovskite film with reduced defect is obtained, consequently promoting the efficiency up to 11.60 % for CsPbIBr 2 and 14.44 % for CsPbI 2 Br carbon-based devices, with excellent durability under harsh conditions. [ABSTRACT FROM AUTHOR]