Constructing Interfacial Gradient Heterostructure Enables Efficient CsPbI 3 Perovskite Solar Cells and Printed Minimodules.

Severe nonradiative recombination originating from interfacial defects together with the pervasive energy level mismatch at the interface remarkably limits the performance of CsPbI 3 perovskite solar cells (PSCs). These issues need to be addressed urgently for high-performance cells and their applications. Herein, we demonstrate an interfacial gradient heterostructure based on low-temperature post-treatment of quaternary bromide salts for efficient CsPbI 3 PSCs with an impressive efficiency of 21.31% and an extraordinary fill factor of 0.854. Further investigation reveals that Br - ions diffuse into the perovskite films to heal undercoordinated Pb 2+ and inhibit Pb clusters formation, thus suppressing nonradiative recombination in CsPbI 3 . Meanwhile, a more compatible interfacial energy level alignment resulting from Br - gradient distribution and organic cations surface termination has been also achieved, hence promoting charge separation and collection. Consequently, we also demonstrate the printed small-size cell with an efficiency of 20.28% and 12-cm 2 printed CsPbI 3 minimodules with a record efficiency of 16.60%. Moreover, the unencapsulated CsPbI 3 films and devices exhibit superior stability. This article is protected by copyright. All rights reserved.