H ₂ O ₂ -Modulated NiO _x Nanoparticle Film with High Conductivity and an Improved Heterojunction for Efficient Sb ₂ Se ₃ Solar Cells

Hole transporting layers (HTLs) play an important role in improving the performance of optoelectronic devices by efficiently transporting holes and blocking the reverse flow of electrons. In this study, we introduce hydrogen peroxide (H 2 O 2 )-modulated NiO x (modulated-NiO x ) as an efficient HTL for antimony selenide (Sb 2 Se 3 ) solar cells. H 2 O 2 improves the dispersion of NiO x nanoparticles in aqueous solution, increases the Ni 3+ /Ni 2+ ratio, and leads to a more uniform and compact NiO x film with superior electronic properties. The increased Ni 3+ /Ni 2+ ratio results in a more matching energy level alignment between NiO x and Sb 2 Se 3 that is favorable for hole extraction. Density functional theory (DFT) calculations reveal that the modulated-NiO x /Sb 2 Se 3 interface exhibits a more ordered and planar interfacial structure with a well-aligned atomic position, promoting efficient charge transfer and suppressing interfacial recombination. As a result, Sb 2 Se 3 solar cells employing modulated-NiO x achieve a power conversion efficiency (PCE) of 9.06%, which ranks among the top efficiency for all-inorganic Sb 2 Se 3 solar cells. Furthermore, the devices exhibit excellent stability, retaining 97% of the initial PCE after 30 days of storage in air. This study highlights the potential of H 2 O 2 -modified NiO x as a high-performance HTL for efficient and stable Sb 2 Se 3 solar cells, providing a promising pathway for advancing the Sb 2 Se 3 photovoltaic technology.