Enhanced passivation durability in perovskite solar cells via concentration-independent passivators

Defect passivation is regarded as an essential strategy for constructing efficient perovskite solar cells. However, the passivation in long-term operation durability has been largely ignored. Passivator concentration is usually optimized using fresh devices, whereas defect concentration increases with time during actual device operation. As a result, the initial passivators with low concentrations fail to passivate growing numbers of defects in a sustainable manner. Higher initial concentrations of passivators could in principle deal with new defects as they develop, but this strategy has not been successful so far because high concentrations of passivators are always harmful to device performance. In this study, we report a type of π-conjugated passivator, the passivation effectiveness of which is independent of its concentration. This unique feature allows for high-concentration passivation without reducing device performance, which considerably improves passivation durability. This study will provide guidance for designing concentration-independent passivators and direct attentions to their passivation durability.