Towards broad range and highly efficient down-conversion of solar spectrum by Er3+–Yb3+ co-doped nano-structured glass-ceramics

The efficiency of semiconductor solar cells could be greatly increased by down-conversion processes, which efficiently split incident solar photons into couples of photons with energy over the bandgap. Here, we show new down-conversion mechanisms in Er3+–Yb3+ co-doped glass-ceramics, where the ions are hosted by fluoride nanoparticles embedded in silica glass. By this means, 350–550 nm photons, absorbed by Er3+ ions, generate pairs of photons at the range of 650–1550 nm, emitted by Er3+ and Yb3+, with a quantum efficiency approaching the maximum of 200%.