Glutamine bridge-connecting at SnO2/Perovskite interface for energy levels alignment and carrier transfer enhancement in perovskite solar cells

Perovskite solar cells (PSCs) encounter challenges in power conversion efficiency (PCE) and stability due to defects at the electronic transport layer (ETL)/perovskite interface. In this work, glutamine (Glu) is employed as a bridge-connecting layer in SnO₂/perovskite(Cs_0.05FA_0.95PbI₃) interface to passivate the complicated defects from SnO₂ and buried perovskite surface simultaneously. Glu modification increases electrical conductivity and shifts up the Fermi level of SnO₂ films facilitating electron transport through amide group interacting with the Sn-related defects and absorbed hydroxyl on SnO₂ surface. On the other hand, the carboxyl group inclined anchors uncoordinated Pb²⁺ and I^- on buried perovskite interface to cure point defects and regulate nucleation achieving high-quality perovskite films. Surprisingly, the device under the bridge-connecting of Glu with multiple groups obtains a marked short current density of 26.10 mA/cm² and a champion power conversion efficiency of 23.40 %. In addition, the unencapsulated PSCs with optimized Glu exhibit gratifying humidity stability, sustaining 87 % of their initial PCE after exposing to highly relative humidity (65 ± 5 %) for 750 h.