Photon management in La2BaZnO5:Tm3+, Yb3+ and La2BaZnO5:Pr3+, Yb3+ by two step cross-relaxation and energy transfer

► Down-conversion for photovoltaics. ► Luminescence study of La2BaZnO5:Tm3+, Yb3+ and La2BaZnO5:Pr3+, Yb3+. ► Energy transfer from Pr3+ to Yb3+ in competition with back-transfer. ► Cross-relaxation between pairs of Tm3+ ions.