In-situ chloride/potassium passivated ZnO nanocrystals for improved charge extraction in PbS quantum dot solar cells

Electron transport layers comprising colloidal ZnO nanocrystals are commonly utilized in PbS quantum dot solar cells. However, the presence of surface defects induced by oxygen vacancies and surface hydroxyls poses a significant obstacle to high-performance device. Consequently, there is an urge for realizing ZnO nanocrystals with reduced surface defects. Herein, we developed an in-situ passivation strategy for synthesizing ZnO nanocrystals, denoted as Cl/K-ZnO, with suppressed surface defects by Cl/K ions. The integration of the Cl/K-ZnO electron transport layer into the photovoltaics has led to a remarkable decrease in surface defects and reasonable energy band alignment for better carrier extraction. Accordingly, we achieved the efficient photovoltaics with a champion power conversion efficiency of 11.17 % and an impressive operational stability, retained 83 % of the initial power conversion efficiency after an operation period of 200 h under AM 1.5 G illumination in N₂ glovebox.