Benign Pinholes in CsPbIBr2 Absorber Film Enable Efficient Carbon-Based, All-Inorganic Perovskite Solar Cells

Pinholes in absorber films are traditionally thought to degrade the performance of perovskite solar cells. The pursuit of efficient cells, especially the large-area ones, has thus mainly focused on realizing full-coverage absorber films. Herein, we demonstrate that such a paradigm can be broken in carbon-based, all-inorganic perovskite solar cells, by taking CsPbIBr2 absorber film as an example. It is revealed that pinholes in one-step solution-processed CsPbIBr2 film will not form detrimental shutting paths in the ultimate cell when the film is relatively thick (similar to 700 nm). We link this surprising finding to the fact that the raw carbon paste cannot penetrate the pinholes during screen-printing deposition of the carbon electrode due to its sticky nature. More importantly, such pinholes are in favor of the formation of desirable crystalline grains in CsPbIBr2 film, thereby inducing greatly suppressed carrier recombination. Consequently, the cells based on CsPbIBr2 films containing benign pinholes yield the outstanding efficiency of 9.06%, which is much higher than that of the ones based on the films without pinholes (6.19%). Hence, our work shows the important progress toward insight of carbon-based, all-inorganic perovskite solar cells in realization of efficient, large-area ones for practical applications.