Realizing mechanical stable and efficient wide-bandgap flexible perovskite solar cells by toughening the buried interface

Wide-bandgap (WBG) flexible perovskite solar cells (pero-SCs) have aroused widespread interest because of their unique advantages in constructing high-efficiency tandems. Nickel oxide (NiOx) is an excellent choice for the hole transport layer of flexible WBG pero-SCs owing to its low-temperature processing and outstanding stability. However, the presence of abundant defects at the buried perovskite layer and the weak binding force at the NiOx/perovskite interface limit the efficiency and mechanical stability of flexible WBG pero-SCs. This study explores a buried interface modification strategy by introducing the functional molecule N-acetyl-L-glutamic acid (NALG) to address the above issues. Theoretical calculation and experimental results show that carboxyl and amide groups of NALG can bond with NiOx and perovskite, respectively, which helps passivate interfacial defects and enhances perovskite crystallization. Moreover, NALG serves as a bridging molecule, significantly improving the toughness of the NiOx/perovskite interface. Consequently, the flexible WBG pero-SC based on NiOx/NALG achieved a power conversion efficiency (PCE) of 16.28% with reduced energy loss. Additionally, these flexible pero-SCs demonstrated robust mechanical durability, retaining 83% of their initial efficiencies after 10000 bending cycles at a radius of 5 mm. Furthermore, the devices exhibited outstanding long-term operational, thermal, and moisture stabilities. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)N-(sic)(sic)-L-(sic)(sic)(sic)(NALG)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)NALG(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic), NALG(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic)(sic)(sic)16.28%(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic)(sic), (sic)(sic)(sic)(sic)10000(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)83% ((sic)(sic)(sic)(sic)(sic) 5 mm). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).