Evaporated potassium chloride for double-sided interfacial passivation in inverted planar perovskite solar cells

Abstract Defect-induced charge carrier recombination at the interfaces between perovskite and adjacent charge transport layers restricts further improvements in the device performance of perovskite solar cells (PSCs). Defect passivation at these interfaces can reduce trap states and inhibit the induced nonradiative recombination. Herein, we report a double-sided interfacial passivation via simply evaporating potassium chloride (DIP-KCl) at both the hole transport layer (HTL)/perovskite and perovskite/electron transport layer (ETL) interfaces in inverted planar PSCs. We demonstrate that the bottom KCl layer at the HTL/perovskite interface not only reduces the interfacial defects and improves the interfacial contact, but also leads to increased perovskite crystallinity, while the top KCl layer at the perovskite/ETL interface efficiently passivates the perovskite top surface defects and facilitates electron extraction at this interface. Thus, suppressed nonradiative recombination and faster charge extraction at both interfaces close to the perovskite layer can be achieved by using our DIP-KCl strategy. As a result, inverted PSCs based on DIP-KCl present an increased efficiency from 17.1% to 19.2% and enhanced stability, retaining over 90% of their initial efficiency after aging at maximum power point tracking for 1000 h. This work provides a simple and efficient way for defect passivation to further increase the efficiency and stability of PSCs.