The power conversion efficiency of most thin film solar cells is compromised by competing optical and electronic constraints, wherein a cell must be thick enough to collect light yet thin enough to efficiently extract current. Here, we introduce a nanoscale solar architecture inspired by a well-known radio technology concept, the coaxial cable, that naturally resolves this “thick–thin” conundrum. Optically thick and electronically thin amorphous silicon “nanocoax” cells are in the range of 8% efficiency, higher than any nanostructured thin film solar cell to date. Moreover, the thin nature of the cells reduces the Staebler–Wronski light-induced degradation effect, a major problem with conventional solar cells of this type. This nanocoax represents a new platform for low cost, high efficiency solar power.