β-NaYF4:Er3+(10%) microprisms for the enhancement of a-Si:H solar cell near-infrared responses

beta-NaYF4:Er3+ (10%) microprisms, synthesized using a hydrothermal method, were applied to the back of a thin film hydrogenated amorphous silicon (a-Si:H) solar cells to investigate response to sub-band gap near-infrared irradiation. Currents of 0.3 mu A and 0.01 mu A were measured during single-illumination with 60 mW (80 mW/cm(2)) 980 nm and 1560 nm diode lasers, respectively, due to frequency upconversion (UC). Under co-excitation by 60 mW 980 nm and 100 mW 1560 nm lasers, a current improvement to 0.54 mu A was obtained, resulting from enhancements in red emission. The finding indicates that co-excitation with multiple wavelengths accessible to UC materials is very effective in enhancing the efficiency of solar cells. (C) 2012 Elsevier B.V. All rights reserved.