Redox-Active NiOx-Catalyzed Li plus Capture-Extraction Strategy for tBP-Free Spiro-OMeTAD Enables Exceptional Damp-Heat Stability in Perovskite Solar Cells

Abstract

For the spiro-OMeTAD-based hole-transporting layer (HTL), despite its widespread implementation, the pragmatic deployment of perovskite solar cells remains profoundly constrained by multifaceted intrinsic challenges-most notably the inclusion of tBP and the deleterious migration behaviors of Li+ ions-which collectively undermine long-term thermal stability, as even advanced encapsulation schemes fail to arrest irreversible performance degradation. Here, we introduce a redox-catalytic strategy that enables simultaneous Li+ capture and extraction from the spiro-OMeTAD solution, achieving a tBP-free, Li+-free dopant system. Micro-sized nickel oxide (NiOx) powder act as a redox-active catalyst, inducing ultrafast oxidation of spiro-OMeTAD through a redox cascade mechanism while promoting LiTFSI solvation and Li+ sequestration. The reacted NiOx particulates, along with sequestered Li+ ions and Li-related byproducts, are completely removed during filtration, yielding a purified dopant formulation devoid of instability-inducing residues. As a direct outcome, the NiOx-catalyzed HTL furnishes an outstanding powder conversion efficiency of 25.24%, commensurate with that of devices employing conventionally doped HTLs containing tBP and LiTFSI. More importantly, the concomitant removal of pernicious constituents imparts exceptional operational resilience, with the device retaining over 95% of its initial efficiency after 1,000 h under stringent damp-heat stress.