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.

Colloidal core/shell quantum dots (QDs) with environment-friendly feature and controllable optoelectronic properties are promising building blocks in emerging solar technologies. In this work, we rationally design and tailor the eco-friendly CuInSe (CISe)/ZnSe core/shell QDs by Mn doping and stoichiometric optimization (i.e., molar ratios of Cu/In). It is demonstrated that Mn doping in In-rich CISe/ZnSe core/shell QDs can effectively engineer the charge kinetics inside the QDs, enabling efficient photogenerated electrons transfer into the shell for retarded charge recombination. As a result, a solar-driven photoelectrochemical (PEC) device fabricated using the optimized Mn-doped In-rich CISe/ZnSe core/shell QDs (Cu/In ratio of 1/2) exhibits improved charge extraction and injection, showing a ~ 3.5-fold higher photocurrent density than that of the pristine CISe/ZnSe core/shell QDs under 1 sun AM 1.5G illumination. The findings indicate that transition metal doping in “green” nonstoichiometric core/shell QDs may offer a new strategy for achieving high-efficiency solar energy conversion applications.