Defect Engineering for Efficient Cu ₂ ZnSnS ₄ Solar Cells via Moisture‐Assisted Post‐Deposition Annealing

Abstract Sulfide kesterite Cu 2 ZnSnS 4 (CZTS) solar cells, containing earth‐abundant and environmentally benign constituents, are regarded as promising candidates for thin‐film photovoltaic technologies. CZTS device performance, however, is currently limited by severe nonradiative recombination caused abundant deep‐level defects. Herein, an effective defect engineering approach high bandgap cells using a newly introduced moisture‐assisted post‐deposition annealing treatment reported. This modifies the local chemical composition within heterojunction grain boundaries enhances incorporation of Cd layer during CdS deposition. not only accumulates at boundaries, but it also presents in interiors where occupies lattice sites. The overall modification environment suppresses deep level defects activates relatively shallow acceptor Zn antisites vacancies, giving rise to remarkably improved performance. work opens new direction materials, which may be applicable other thin film semiconductors.