Accelerating photocarrier dynamics by constructing 2D-3D homojunction toward boosting self-powered UV photodetection

Heterojunction structures are favored for constructing photoelectrochemical ultraviolet photodetectors (PEC UV PDs), whereas lattice mismatches impede their optoelectronic performance. This work presents a novel homojunction consisting of two-dimensional (2D) In₂O₃ nanosheets (NS) and three-dimensional (3D) In₂O₃ microcubes (MC) with a suitable energy band alignment. 2D In₂O₃ NS not only shows an enlarged bandgap due to the quantum confinement effect but also effectively upshifts the conductive band and Fermi level stemming from the oxygen vacancy demonstrated by the theoretical simulation and experimental results. The photogenerated carrier dynamic of In₂O₃ photoanodes is boosted by the 2D-3D homojunction with a built-in electric field and more electrochemically active sites, leading to higher photogenerated carrier separation efficiency, faster interfacial charge transfer, and better self-powered capability. The In₂O₃ 2D-3D homojunction PEC UV PDs exhibit outstanding self-powered deep-UV photoresponse at 0 V, with an ultrahigh responsivity of 316.5 mA/W for 254 nm light, a fast response speed of 15/15 ms, high detectivity of 1.12 × 10¹² Jones, and an outstanding UV-vis rejection ratio of 1507, surpassing most recorded PEC UV PDs. This work demonstrates the pivotal role of morphology-controlled homojunction in modulating photogenerated carrier dynamics and offers a new strategy for designing high-performance PEC devices.