Constructing InP/ZnSe Quantum Dots with Shell Gradient In<sup>3+</sup> Doping for Photoelectrochemical Cells
Qian Zheng, Junfeng Wang, Fei Huang, Zheng Huang, Shuyu Tian, Qing Chen, Yi Pei, Kaibo Zheng, Jianjun Tian
Abstract
Environmentally friendly InP/ZnSe core/shell quantum dots (QDs) with high absorption coefficients and tunable band gaps have demonstrated great potential for photoelectrochemical (PEC) water splitting. However, the tightly bound excitonic feature by inherent type I band alignment tends to reduce the charge separation efficiency, limiting their PEC performance. Herein, we devised heterovalent In 3+ gradient doping in the ZnSe shell of InP QD to construct core/shell structural InP/ZnSe-G-In QDs. The In 3+ dopant increased the Fermi level of the ZnSe shell; thus continuous semiconductor homojunction and band bending were formed by gradient composition doping, which accelerates the exciton separation through the built-in electric field. As a result, the PEC cells based on such QDs exhibited high photocurrent density of 8.7 mA/cm 2, demonstrating one of the highest values for the InP-based QDs PEC cells. This work provides an effective strategy for the application of type I band structure QDs in solar energy conversion.