Less-acidic boric acid-functionalized self-assembled monolayer for mitigating NiO<sub>x</sub> corrosion for efficient all-perovskite tandem solar cells.

Wang, Jingnan; Jiao, Boxin; Tian, Ruijia; Sun, Kexuan; Meng, Yuanyuan; Bai, Yang; Lu, Xiaoyi; Han, Bin et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The interfacial contact between NiO<sub>x</sub> 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 NiO<sub>x</sub>, undermining device stability. Moreover, SAM aggregation leads to interfacial losses and significant open-circuit voltage (V<sub>OC</sub>) deficits. Here, we introduce boric acid (BA) as a milder anchoring group that chemisorbs onto NiO<sub>x</sub> via strong - <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>BO</mi></mrow> <mrow><mn>2</mn></mrow> </msub> <mstyle><mtext>-</mtext></mstyle> </math> -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.