Synergic interface passivation with potassium citrate as an eco-friendly conductive adhesive in perovskite solar cells

Oxygen vacancies on the surface of the electron transport layer (ETL) can distort the perovskite structure near the interface, inducing unfavorable phases, and, the surface chemical modification of the ETL plays a key role for the efficiency and stability of perovskite solar cells (PSCs). In this study, C6H5K3O7 was introduced as a conductive adhesive to modify the SnO2/perovskite interface. The polar molecule group (-C6H5O7) could react with the perovskite to trigger heterogeneous nucleation over the perovskite precursor film for a high-quality perovskite, which not only decreases the bulk defects, but also interacts with excess PbI2 to passivate the interface defect. Meanwhile, interstitial K+ could modulate the perovskite growth and upshift the energy barrier of ion migration, which significantly suppresses non-radiative recombination. Moreover, -C6H5O7 could react with SnO2 to reduce its surface oxygen vacancies and optimize the band alignment of SnO2, which matches with that of perovskite. These are beneficial for the better interfacial contact of the ETL with the perovskite, forming more channels for electron transfer and achieving self-encapsulation at the buried interface. Therefore, the C6H5K3O7-based PSC achieved a champion efficiency of 24.12% with negligible J-V hysteresis. In addition, its initial power conversion efficiency can remain over 90% after 2400 h storage in dry air with good stability.