A light emitter includes a substrate, a first light-emitting layer, a blocking layer and a second light-emitting layer. The second light-emitting layer is disposed on the blocking layer, the blocking layer is disposed on the second light-emitting layer and the first light-emitting layer is disposed on the blocking layer. The first light-emitting layer, the blocking and the second light-emitting layer form a P-N-P junction. The first light-emitting layer and the blocking layer form a first electroluminescent unit, and the blocking layer and the second light-emitting layer form a second electroluminescent unit. The first electroluminescent unit and the second electroluminescent unit build a back-to-back bipolar junction. |