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 ultraviolet–visible (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.

Self-powered photoelectrochemical (PEC) photodetectors hold great promise for underwater optical applications, yet suffer from sluggish carrier dynamics and limited stability. Herein, high-performance, self-powered, and stable PEC ultraviolet (UV) photodetectors were fabricated using metal-organic-framework derived ZnO nanocages (NCs). These topography-engineered ZnO NCs synchronously enhance UV absorption, facilitate photogeneration carrier separation, and promote charge transfer at the ZnO/electrolyte interface, thus optimizing the overall photoresponse performance. The ZnO NCs-based PEC device achieves an ultrahigh responsivity of 300.6 mA/W under 365 nm UV light irradiation, a fast response time of 10/20 ms, outstanding spectra selectivity (UV/visible rejection ratio of 2000), and excellent cycling stability (10,000 cycles), which is one of the best reported PEC UV photodetectors. Furthermore, the self-powered ZnO-based PEC PDs have good underwater optical imaging capability. This work provides a new idea for designing high-performance UV photodetectors for application in underwater environments.

Transparent solar-blind ultraviolet photodetectors (SBUV PDs) have extensive applications in versatile scenarios, such as optical communication. However, it is still challenging to simultaneously achieve high responsivity, high transparency, and satisfying self-powered capability. Here, we demonstrated high-performance, transparent, and self-powered photoelectrochemical-type (PEC) SBUV PDs based on vertically grown ultrathin In₂O₃ nanosheet arrays (NAs) with a three-dimensional (3D) porous structure. The 3D porous structure simultaneously improves the transmittance in the visible light region, accelerates interfacial reaction kinetics, and promotes photogenerated carrier transport. The performance of In₂O₃ NAs photoanodes exceeds most reported self-powered PEC SBUV PDs, exhibiting a high transmittance of approximately 80% in the visible light region, a high responsivity of 86.15 mA/W for 254 nm light irradiation, a fast response speed of 15/18 ms, and good multicycle stability. The In₂O₃ NAs also show excellent spectral selectivity with an ultrahigh solar-blind rejection ratio of 1319.30, attributed to the quantum confinement effect induced by the ultrathin feature (2–3 nm). Furthermore, In₂O₃ NAs photoanodes show good capability in underwater optical communication. Our work demonstrated that a 3D porous structure is a powerful strategy to synchronously achieve high responsivity and transparency and provides a new perspective for designing high-performance, transparent, and self-powered PEC SBUV PDs.