Concentrating optics are integrated into up-conversion photovoltaic (UC-PV) devices to independently concentrate sub-band-gap photons on the up-conversion layer, without affecting the full solar concentration on the overlying solar cell.One of the concentrators used in this study (parabolic) with a bifacial silicon solar cell attached. The UC phosphor is attached on the exit aperture of the parabolic concentrator. For details, see B. S. Richardset al. Opt. Express 22, A452-A464 (2014).