Self-powered ultraviolet vertical and lateral photovoltaic effect with fast-relaxation time in NdNiO₃/Nb:SrTiO₃ heterojunctions

Substantial ultraviolet (UV) photodetector research has been pursued in recent decades. In this paper, we report the self-powered UV vertical photovoltaic effect (VPE) and lateral photovoltaic effect (LPE) with high sensitivity and fast-relaxation time in NdNiO₃/Nb:SrTiO₃ (NNO/NSTO) heterojunctions. The rectifying behavior indicates that the large built-in electric field is formed in the p-n junctions. The open circuit voltage of VPE is as high as 0.4 V under 266 nm laser illumination, with the relaxation time of 1.8 μs. The highest position sensitivity of the LPE is about 32 mV/mm, and its optical relaxation time is about 7.4 μs. The two distinct resistance states observed for the NNO film deposited on NSTO and SrTiO₃ (STO) substrates suggest that the transport of photo-excited carriers in VPE and LPE is mainly through the NSTO single crystal, resulting in a fast relaxation time of the photovoltaic effect in NNO/NSTO p-n junctions. The fast relaxation and high sensitivity of the VPE and LPE make the NNO/NSTO junction a promising candidate for a wide range of self-powered ultraviolet/near-ultraviolet optoelectronic applications.