Improving and manipulating green-light electroluminescence in solution-processed ZnO nanocrystals via erbium doping

Regulating green electroluminescence (EL) of ZnO is an important but difficult task to produce white-light sources due to its strong background green emission. We have demonstrated that the green EL from solution-processed ZnO nanocrystals (NCs) can be improved and manipulated by erbium (Er) doping. Er3+ ions can be doped and activated without any high-temperature post-annealing treatment. Incorporation of the Er3+ ions in the ZnO host induces lattice expansion primarily along the (002) direction. Er3+-related characteristic green emissions are observed at 535 and 556 nm and manipulated with increasing Er concentration under forward bias. The EL mechanism is investigated and found to be driven by the energy transfer from the deep-level defects of the ZnO NCs to the nearby Er3+ ions. Our findings have demonstrated the feasibility of producing green light-emitting diodes by solution-processable Er-doped ZnO NCs and inspired a promising way to develop white-light sources based on printable ZnO NCs simply by incorporating different rare earth ions into the ZnO NCs simultaneously.