Less-acidic boric acid-functionalized self-assembled monolayer for mitigating NiOx corrosion for efficient all-perovskite tandem solar cells
Jingnan Wang, Boxin Jiao, Ruijia Tian, Kexuan Sun, Yuanyuan Meng, Bai Yang, Xiaoyi Lü, Bin Han, Ming Yang, Yaohua Wang, Shujing Zhou, Haibin Pan, Zhenhuan Song, Chuanxiao Xiao, Chang Liu, Ziyi Ge
Abstract
The interfacial contact between NiOx and self-assembled monolayers (SAMs) in wide-bandgap (WBG) subcells limits the efficiency and stability of all-perovskite tandem solar cells (TSCs). The strongly acidic phosphoric acid (PA) anchors in common PA-SAMs corrode reactive NiOx, undermining device stability. Moreover, SAM aggregation leads to interfacial losses and significant open-circuit voltage (VOC) deficits. Here, we introduce boric acid (BA) as a milder anchoring group that chemisorbs onto NiOx via strong – $${{\rm{BO}}}_2{\mbox{-}}$$ –Ni coordination. A benzothiophene-fused head group enhances interfacial bonding through S–Ni orbital interactions, yielding higher binding energy than PA-SAMs. This design also promotes homogeneous SAM formation without aggregation. Resultantly, the WBG cell exhibits an improved PCE to 20.1%. When integrated with narrow bandgap (NBG) subcell, the two-terminal (2T) TSCs achieve an ameliorative PCE of 28.5% and maintain 90% of the initial PCE after maximum power point tracking (MPP) under 1 sun illumination for 500 h. The suboptimal interfacial contacts between nickel oxide and self-assembled monolayers in wide bandgap subcells limit the photovoltaic efficiency and stability. Here, authors employ boric acid as an anchoring group for chemisorption, achieving efficiency of 28.5% for two-terminal tandem solar cells.