Enhanced electroluminescence from n-ZnO NCs/n-Si isotype heterojunctions by using i-NiO as electron blocking layer

Solution-processed n-ZnO nanocrystals (NCs)/n-Si isotype heterojunction light-emitting diodes (LEDs) were fabricated and characterized. Electroluminescence (EL) of the n-ZnO NCs/n-Si LEDs was drastically boosted more than fivefold by introducing an effective i-NiO electron blocking layer (EBL). Peak deconvolution results suggested that the green and orange emissions related to oxygen defects in ZnO NCs were enhanced so significantly that the emission color was tuned from bluish green toward greenish yellow. Photoluminescence (PL) and time-resolved PL investigations revealed that i-NiO can also act as a superior hole transport layer to reduce the carrier lifetime from 0.354 to 0.307 ns. Our results show the great potential of utilizing i-NiO as an effective EBL to fabricate printed optoelectronic devices based on solution-processed n-ZnO NCs/Si heterojunctions.