Engineering the Optoelectronic Properties of Colloidal Alloyed Copper Chalcogenide Quantum Dots for High‐Efficiency Solar Energy Conversion

Abstract

Colloidal alloyed copper chalcogenide Cu2 − xSe1 − ySy (CuSeS) quantum dots (QDs) are promising building blocks for solar energy applications because of their unique size/composition‐tunable optical bandgap, which is well matched to the sunlight spectrum. Nevertheless, poor charge separation/transfer and low photostability induced by their intrinsically abundant surface defects/traps tremendously hinder the realization of high‐performance solar energy conversion systems such as solar‐driven photoelectrochemical (PEC) devices. Herein, the synthesis of copper chalcogenide CuSeS core QDs with effective CdS shell passivation is presented. These core/shell QDs exhibit optimized optoelectronic properties with a particularly ultralong lifetime, indicating the formation of type‐II band structure for efficient spatial charge separation, which is further probed using ultrafast transient absorption (TA) spectroscopy. To demonstrate the feasibility of solar energy conversion, solar‐driven PEC cells using such core/shell QDs as light‐converters are fabricated, yielding an impressive saturated photocurrent density of ≈4 mA cm−2 with preeminent durability under 1 sun illumination. This finding highlights a potential technique to engineer the optoelectronic properties of colloidal alloyed copper chalcogenide nanomaterials for high efficiency and stable solar energy conversion devices.