Understanding and controlling the interaction of light, charge, and materials at the atomic scale is key to developing the next generation of sustainable energy technologies. To address these challenges, we design and develop advanced semiconducting materials and functional interfaces, with a focus on thin films and their heterostructures for solar energy conversion, electrocatalysis, and optoelectronics. Through our research, we aim to uncover and direct optical excitations, charge carrier transport mechanisms, and interfacial dynamics. To gain new insights into these fundamental processes, we combine advanced deposition methods, including reactive sputtering, atomic layer deposition, and molecular beam epitaxy, with a comprehensive suite of (in situ) structural, elemental, and optoelectronic characterization tools. This integrated approach enables us to interrogate and guide complex light-to-charge and charge-to-chemical transformation pathways that underlie the functional characteristics of emerging optoelectronic and energy conversion systems.