Spin-polarized colloidal quantum dots for highly efficient magnetic field-assisted photoelectrochemical solar energy conversion

Manipulating the intrinsic properties of colloidal quantum dots (QDs) to rationally construct a photoelectrochemical (PEC) device with exceptional solar-to-hydrogen conversion efficiency is a promising technology towards future global carbon neutrality. In this work, inherent electron spin polarization was introduced into CuInGaS (CIGS) QDs through magnetic Mn incorporation to realize a high-performing magnetic field-assisted solar-driven QDs-based PEC hydrogen generation system. Experimental and theoretical studies revealed that the induced spin-polarized electrons by magnetic element doping remarkably promoted the photogenerated carrier transfer/separation of QDs and corresponding photoelectrodes without modifying their structural/morphological features and light-absorption ability. Additionally, the nonradiative charge recombination within spin-polarized Mn-CIGS QDs-based photoelectrodes was more significantly suppressed when an external magnetic field was applied, which is ascribed to the synergistic effect of enhanced spin-polarized electrons and magnetic field-assisted photogenerated carrier migration. As a result, with the assistance of external magnetic field, as-fabricated spin-polarized QDs-based PEC cell exhibited an outstanding saturated photocurrent density of 14.7 mA cm −2 under 1 sun AM 1.5 G illumination (100 mW cm −2 ). Our findings offer new insights in tailoring the spin polarization characteristics of QDs to optimize the photoinduced charge dynamics for high-efficiency magnetic field-assisted solar energy conversion applications.