Synchronous engineering on carriers and stability in TiO₂ electron transport layer for efficient perovskite solar cells

TiO₂-based electron transport layers (ETLs) have been widely employed in planar perovskite solar cells (PSCs) but are limited by their low intrinsic electron mobility and inadequate light stability. The present work demonstrates an efficient strategy for the synchronous engineering of charge transport and light stability in TiO₂-based PSCs by embedding laser-derived La-doped BaSnO₃ (LBSO) nanocrystals into TiO₂ ETLs. LBSO nanocrystals facilitate the formation of rutile-phase TiO₂, which is inactive for photocatalysis. Thus, the light stability of PSCs is favored. Moreover, the embedding of high-conductivity LBSO nanocrystals increases the electron mobility of TiO₂ ETLs by two orders of magnitude, accelerating photogenerated carrier extraction at the TiO₂-perovskite heterointerface of PSCs. More importantly, the resulting TiO₂-LBSO hybrid ETLs promote the growth of the top perovskite film, resulting in increased grain size and fewer defect states. Consequently, the power conversion efficiency (PCE) of PSCs employing such ETLs increases to 25.90 % from the pristine 23.86 %, with significantly enhanced operational stability. After continuous illumination is performed in a N₂ atmosphere for 1150 h at 100 mW/cm², the devices still retain more than 80 % of the initial PCE. These results indicate that embedding LBSO nanocrystals in TiO₂ ETLs is an effective approach that could address the stability and efficiency of PSCs simultaneously.