Nanophotonic resonators for InP solar cells.

We describe high efficiency thin-film InP solar cells that utilize a periodic array of TiO2 nanocylinders. These nanophotonic resonators are found to reduce the solar-weighted average reflectivity of an InP solar cell to ~1.3%, outperforming the best double-layer antireflection coatings. The coupling between Mie scattering resonances and thin-film interference effects accurately describes the optical enhancement provided by the nanocylinders. The spectrally resolved reflectivity and J-V characteristics of the device under AM1.5G illumination are determined via coupled optical and electrical simulations, resulting in a predicted power conversion efficiency > 23%. We conclude that the nanostructured coating reduces reflection without negatively affecting the electronic properties of the InP solar cell by separating the nanostructured optical components from the active layer of the device.