Engineering built-in electric fields and ligand-to-metal charge transfer in CdS/Ni-MOF heterostructures toward high-performance photo-assisted supercapacitors.

Photo-assisted supercapacitors (PASCs) integrate solar-energy harvesting and electrochemical energy storage, but their performance is limited by inefficient photocarrier separation and sluggish charge-transfer kinetics. Herein, a CdS/Ni-MOF heterostructure photoelectrode is constructed via an in situ growth strategy. Visible-light-responsive CdS broadens light absorption and induces a built-in electric field (BIEF) at the CdS/Ni-MOF interface, while ligand-to-metal charge transfer (LMCT) within Ni-MOF further accelerates carrier migration and redox kinetics. Experimental results and DFT calculations confirm that the synergistic BIEF and LMCT suppress charge recombination and promote directional electron transport. Consequently, the assembled flexible integrated photo-assisted supercapacitor (IPSC) delivers an energy density of 115.4 Wh kg-1 at a power density of 2247 W kg-1 under illumination, with a 58% capacitance enhancement over dark conditions. The device also exhibits reversible photo-response, cycling stability, and mechanical flexibility, providing a promising strategy for high-performance photo-assisted energy-storage systems.