Ultrastable colloidal quantum dots-based photoelectrochemical photodetectors for weak-light underwater optical communication

Photoelectrochemical (PEC) photodetectors (PDs) enabling high sensitivity/stability and self-powered operation in undersea weak-light environments is significant to the development of underwater optical communication (UOC) application. However, to date, the UOC system based on weak light-driven PEC PDs has rarely been investigated, primarily due to the lack of functional material and relevant heterojunction photoelectrodes with efficient weak light harvesting, fast response time and high stability. Herein, we introduced the Al doping in colloidal CuInS₂ (CIS) quantum dots (QDs) to suppress the non-radiative recombination and induce the self-oxidation Al₂O₃ protective layer for largely enhanced photo-/chemical stability. The prepared Al-doped CIS QDs were used to decorate BiVO₄ (BVO) as photoelectrodes for the fabrication of PEC PD devices, which delivered a maximum responsivity of 1 A W^-1, a detectivity of 1.02 × 10¹² Jones, fast response time (26/25 ms) and ultrastable long-term stability (performance nearly unchanged after 36-hour stability test), thus demonstrating the UOC application even under a weak-light intensity of 0.14 mW cm^-2. The results manifest the potential of rationally designed QDs/metal oxide photoelectrode to achieve highly efficient and stable PEC PDs for next-generation weak-light UOC applications.