The improvement of near-ultraviolet electroluminescence of ZnO nanorods/MEH-PPV heterostructure by using a ZnS buffer layer

A near-ultraviolet light emitting diode (LED) consisting of ZnO nanorods/MEH-PPV heterostructure and a layer of ZnS as the modification buffer layer is reported. Specially, the ZnO nanorods are grown on the ZnS hole-injecting buffer layer by hydrothermal method. Then the devices of ITO/ZnS/ZnO/ZnOnanorods/MEH-PPV/Al are prepared. Under forward bias, not only strong near-ultraviolet (N-UV) electroluminescence (EL) at 380 nm of ZnO band edge emission and weak defect-related emissions of ZnO nanorods at 410, 510 and 760 nm are observed, but also the exciton emission of MEH-PPV at 580 nm is detected. Along with increasing the thickness of ZnS film, the emission at 580 nm strengthens. Compared with the device ITO/ZnO/ZnOnanorods/MEH-PPV/Al we have reported in the past, the experimental results show that the suitable insertion of a ZnS thin layer can enhance the N-UV EL. Under the same voltage, the light intensity can be increased up to 10 times more than that of the device without a ZnS layer. Moreover, the turn-on voltage is reduced remarkably. The effect of ZnS as the hole-injecting buffer layer with different thickness on the EL of ZnO nanorods/MEH-PPV heterostructure is investigated. (C) 2010 Elsevier B. V. All rights reserved.