Our major goal of STORE-LIGHT is to develop a fully functional stand-alone photo-storage system that can be used to drive external devices. Towards this aim we have employed semiconductor metal oxide (MO) nanocrystals (NCs), such as indium tin oxide (ITO) NCs as light-harvesting and energy-storing materials. We first prepared and characterized them on a small scale. After synthesizing these structures, we analyzed their optical response through spectroscopic techniques. These doped materials can absorb UV light (above the band gap) and store photogenerated electrons, a phenomenon known as photodoping, which lies at the core of our project. We then focused on understanding the mechanisms behind charge accumulation and ways to improve it. To enhance the electron storage ability of ITO NCs, we explored the use of specific hole scavengers. Next, we produced electrodes as thin films based on ITO NCs using different solution-processing deposition techniques. We then integrated a sensitizers with the ITO NCs electrodes to extend their absorption into the visible light range. Finally, we prepared hybrid structures combining ITO NCs and the sensitizer, and characterized their capacitance under light and dark conditions using photo-electrochemical methods. The prepared photoelectrodes were used as working electrodes to fabricate two terminal photocapacitors with a simple design. Device performance under solar illumination was evaluated using photoelectrochemical techniques like cyclic voltammetry (CV) and galvanostatic charge discharge (GCD). These tests showed the MO layer increased capacitance by about 56% compared to the blank device, with illumination boosting it from 30% to 70%, reaching 10-19 µF/cm². To measure charges truly photostored, we applied the light charge–resistor discharge (LCRD) method, resulting in a specific capacitance of 4.5 µF/cm². Our results demonstrate functional photo-electrodes integrated into photo-supercapacitor-like devices for future solar energy technologies.
