Upconversion nanophosphors for solar cell applications

Currently, one of the major factors limiting the efficiency of solar cells is the spectral mismatch between the energy distribution of photons in the incident solar spectrum and the bandgap of a semiconductor material. To reduce spectral mismatch losses, wavelength conversion of sunlight is regarded as an effective route. Both upconversion and downconversion materials are currently being explored as spectral converters for solar cells. In an upconversion process, photons with energy lower than the band gap of the solar cell are converted to higher energy photons that can be absorbed by the semiconductor. This review focuses on the various synthetic approaches to upconversion nanocrystals and methods to improve upconversion luminescence, as well as it gives an overview of the recent developments in the photovoltaic applications of upconversion nanomaterials.