Self-powered polycrystalline SrSnO3/NiO heterojunction for ultra-stable and high-responsivity ultraviolet photodetection

Strontium stannate (SrSnO3), an emerging wide-bandgap semiconductor, holds great promise for ultraviolet (UV) photodetectors in space and flame detection applications; yet, its development has been constrained by a reliance on single-crystal material quality. Herein, we overcome this critical limitation by constructing an all-oxide p–n heterojunction between polycrystalline La-doped SrSnO3 (n-type) and epitaxial NiO (p-type). The heterostructure achieves solar-blind UV detection at 254 nm with high performance. The optimized device delivers a responsivity of 31.83 mA W−1, a detectivity of 1.36 × 1012 Jones, an ultrafast response (rise/fall times = 18.0/27.9 ms), and an exceptional photocurrent-to-dark-current ratio (>1700). The device also shows excellent environmental stability, with a photocurrent loss of less than 1% after 100 on/off operating cycles and after one year of exposure to ambient atmosphere. This work establishes a general strategy for developing high-performance SrSnO3 photodetectors through heterojunction engineering, broadening the material design space beyond crystalline perfection.