Up-conversion (UC) is the generation of one higher energy visible/near infrared (NIR) photon for two or more lower energy (NIR) photons. Most commercial applications for UC materials require the emission of visible light. A silicon solar cell is able to absorb NIR radiation and is not constrained to just visible light. Infrared luminescence has yet to be thoroughly investigated. Erbium-doped fluoride-based UC phosphors with known visible and NIR emission were attached to the rear of a bi-facial silicon solar cell. The external quantum efficiency (EQE) of solar cell system is reported and compared with the absorption properties of the phosphors.