Colored ultrathin hybrid photovoltaics with high quantum efficiency

Most current solar panels are fabricated via complex processes using expensive semiconductor materials, and they are rigid and heavy with a dull, black appearance. As a result of their non-aesthetic appearance and weight, they are primarily installed on rooftops to minimize their negative impact on building appearance. The large surfaces and interiors of modern buildings are not efficiently utilized for potential electric power generation. Here, we introduce dual-function solar cells based on ultrathin dopant-free amorphous silicon embedded in an optical cavity that not only efficiently extract the photogenerated carriers but also display distinctive colors with the desired angle-insensitive appearances. Light-energy-harvesting colored signage is demonstrated. Furthermore, a cascaded photovoltaics scheme based on tunable spectrum splitting can be employed to increase power efficiency by absorbing a broader band of light energy. This study pioneers a new approach to architecturally compatible and decorative thin-film photovoltaics. Ultrathin solar cells that can also act as coloured signs and displays have been developed by scientists in the USA. Kyu-Tae Lee and co-workers from the University of Michigan fabricated them by embedding a very thin (10–30 nm) layer of amorphous silicon within a metal–semiconductor–metal optical cavity. The cavity acts as a Fabry–Pérot resonator that reflects a particular colour; importantly, it is insensitive to the polarization state or angle (up to 60°) of the incident light. By combining cells of different thickness (and hence different colours), arbitrary patterns or images can be created. The design has yielded solar cells with power conversion efficiencies of around 3%, despite using an amorphous silicon layer that is ten times thinner than those usually found in solar cells.