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

► The upconversion properties of β-NaYF4:Er3+(10%) were studied. ► Current of 0.3 μA for a-Si:H solar cells was measured under 60 mW 980 nm excitation. ► Current of 0.01 μA was measured under 60 mW 1500 nm excitation. ► Under co-excitation conditions, a current improvement of 0.54 μA was obtained.