Modulating defect density of NiO hole transport layer via tuning interfacial oxygen stoichiometry in perovskite solar cells

[Display omitted] •A systematic control of oxygen stoichiometry at NiOx/perovskite interface by thermal treatment.•PSCs with r-NiOx show 20% improved PCE and extended stability in comparison to other counterparts.•A higher defect density at the o-NiOx/perovskite interface leads to poor performance a...

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