Intense 974 nm emission from ErxYb2−xSi2O7 films through efficient energy transfer up-conversion from Er3+ to Yb3+ for Si solar cell

The optical properties of the ErxYb2−xSi2O7 thin films were investigated by photoluminescence measurements and the intense 974 nm light emission was observed. The 974 nm emission was mainly from the transition 2F5/2 to 2F7/2 level of Yb3+ upon exploring energy-transfer via up-conversion at Er3+ 4I13/2 level. Under 972 nm excitation, the lifetime at Er3+ 4I13/2 level reaches up to 4 ms for film containing 2 at% Er3+, while decreases to about 20 μs as the film is pumped by 488 nm. This confirmed that the energy transfer up-conversion process was the dominant transition at Er3+ 4I13/2 level. This may be of interest to improve the solar cells′ efficiency by placing this film at the rear of cell, converting the near-infrared photons between 1480 nm and 1580 nm to just above the Si bandgap.