Conformal Electroplating of Azobenzene-Based Solar Thermal Fuels onto Large-Area and Fiber Geometries

There is tremendous growth in fields where small functional molecules and colloidal nanomaterials are integrated into thin films for solid-state device applications. Many of these materials are synthesized in solution and there often exists a significant barrier to transition them into the solid state in an efficient manner. Here, we develop a methodology employing an electrodepositable copolymer consisting of small functional molecules for applications in solar energy harvesting and storage. We employ azobenzene solar thermal fuel polymers and functionalize them to enable deposition from low concentration solutions in methanol, resulting in uniform and large-area thin films. This approach enables conformal deposition on a variety of conducting substrates that can be either flat or structured depending on the application. Our approach further enables control over film growth via electrodepsition conditions and results in highly uniform films of hundreds of nanometers to microns in thickness. We demonstrate that this method enables superior retention of solar thermal fuel properties, with energy densities of ∼90 J/g, chargeability in the solid state, and exceptional materials utilization compared to other solid-state processing approaches. This novel approach is applicable to systems such as photon upconversion, photovoltaics, photosensing, light emission, and beyond, where small functional molecules enable solid-state applications.