Understanding the up-conversion dynamics in high efficiency Yb3+–Tm3+ systems for solar cells

Up-conversion emission processes have been studied in a transparent oxyfluoride nano-structured glass–ceramic co-doped with Yb3+ and Tm3+ ions. The decay and rise times, and pump power dependence of the different emission peaks have been analysed. The aim was to achieve a complete picture of the dynamics in this multiphoton excitation system. A method based on balance equations for the involved energy levels has been proposed in order to evaluate the up-conversion and decay rates from these levels. The results are analysed from the point of view of potential application to photovoltaic cells.

► Up-conversion luminescence dynamics in high efficiency Yb3+–Tm3+ systems is analysed.
► A method based on balance equations for the involved energy levels is proposed.
► Up-conversion rates become larger than emission decay rates for Tm3+excited levels.
► With low Tm3+ concentration, 4-photons up-conversion processes are avoided.
► The favoured blue-red 3-photons emissions are useful for a-Si and dye solar cells.