Designing of 0D/2D mixed-dimensional van der waals heterojunction over ultrathin g-C3N4 for high-performance flexible self-powered photodetector

Mixed-dimensional van der Waals heterojunctions have attracted a great deal of attention due to their excellent photoelectric conversion capability, which have been widely applied for self-powered photoelectrochemical (PEC)-type devices as the growing demands of clean energy, environmental governance and protection, and the underwater communications. In this work, 0D Bismuth quantum dots (Bi QDs) encapsulated 2D g-C3N4 nanosheets (g-C3N4@Bi) mixed-dimensional heterojunctions were prepared and spined on ITO-coated polyethylene terephthalate (PET) substrate for working as self-powered PEC-type photodetector (PD). Density functional theory calculations evidenced the successful construction of a type II van der Waals heterojunction between g-C3N4 and Bi as well as its enhanced optoelectronic characteristics. Benefiting from the superior properties of g-C3N4@Bi, the as-prepared PD exhibits a high photocurrent of 5.02 μA cm−2, a responsivity of 2843.14 μA W−1, and a specific detectivity of 2.25 × 1011 Jones at 0 V. Furthermore, the PD exhibits self-powered capability after 1000 cycles of bending, and the stable and repeatable ON/OFF signals can be detected over 90 days, indicating the excellent long-term stability and the potential of g-C3N4@Bi-based PD in practical applications.