Solar Energy, Vol.171, 40-46, 2018
Enhanced near-infrared response of a silicon solar cell by using an up-conversion phosphor film of Yb/Er - co-doped CeO2
Co-doped CeO2 thin films were grown from a bulk target with starting composition Ce0.95Yb0.04Er0.01O2 by pulsed laser deposition (PLD) on a p(+)-n-n(+) single crystal silicon diode. The PLD laser fluence was varied between 1.7 J/cm(2) and 3.7 J/cm(2). The device with the film grown for a laser fluence of 2.3 J/cm(2) delivers the highest performance taking advantage of the up conversion (UC) effect provided by this film. Namely, the increase in the relative power conversion efficiency of the device is 12.1% and 39.2% for illumination under 1 and 2.1 sun, respectively, and its relative external quantum efficiency is 8.2% when illuminated with 980 nm light. The film grown for the optimum 2.3 J/cm(2) fluence shows good target-film composition transfer and a granular morphology with a low roughness. The UC mechanism consists of efficient energy transfer between spatially separated Yb3+ and Er3+ ions, i.e. the absorption of infrared light photons by the Yb3+ ions (F-2(7/2) -> F-2(5/2) transition) is followed by a two-step energy transfer process to neighboring Er3+ ions and by their characteristic luminescent emissions ((H-2(11/2), S-4(3/2)) -> I-4(15/2)) and (F-4(9/2) -> I-4(15/2)).
Keywords:Yb and Er co-doped CeO2;Thin films;Up-conversion luminescence;Solar cell;Power conversion efficiency