Intense red electroluminescence from ZnO: Sm3+/Tb3+ LED by efficient energy transfer from Tb3+ to Sm3+

Nowadays, though blue and green GaN-based light-emitting diodes (LEDs) are already successfully commercialized, full-color displays via GaN-based LEDs are difficult to realize due to the low output power of red GaN-based LEDs. Hence, highly efficient red LEDs should be studied. Herein, ZnO:Sm LED was prepared via magnetron co-sputtering. Orange-red electroluminescence originated from f-f transitions of Sm³⁺ is obtained from the device by applying a DC voltage. To enhance the emission of Sm³⁺, Tb was introduced in the ZnO:Sm film via co-sputtering. With a proper Tb concentration, the red emission from the ITO/ZnO: Sm, Tb/n-Si LED can be enhanced dramatically. Notably, the electroluminescence intensity is greatly dependent on the annealing temperature of ZnO:Sm/Tb layer. Therefore, influence of the annealing temperature on the morphology and crystalline structure of the ZnO:Sm/Tb film was investigated. Under a smaller input power, the electroluminescence intensity from the ITO/ZnO:2.1 mol% Sm, 3.4 mol% Tb/n-Si device is one order of magnitude higher than that of the ITO/ZnO:2.1 mol% Sm/n-Si device due to the energy transfer from Tb³⁺ to Sm³⁺. This results demonstrate the EL intensity from trivalent rare earth ions doped-inorganic semiconductor are expected to be greatly enhanced via an efficient ET from another co-doping RE ions as we recently reported. Besides, color of the EL emission move to the red direction after Tb doping. These results offering new ideas for highly efficient red LED used in full-color displays.