Light-emitting diodes based on n-ZnO nano-wires and p-type organic semiconductors

Paper i proceeding, 2008

After our recent successful demonstration of high brightness white light emitting diodes (HB-LEDs) based on high temperature grown n-ZnO nanowires on different p-type semiconductors, we present here LEDs fabricated on n-ZnO nano-wires and p-type organic semiconductors. By employing a low temperature chemical growth (⩽ 90 °C) approach for ZnO synthesis combined together with organic p-type semiconductors, we demonstrate high quality LEDs fabricated on a variety of different substrates. The substrates include transparent glass, plastic, and conventional Si. Different multi-layers of p-type organic semiconductors with or without electron blocking layers have been demonstrated and characterized. The investigated p-type organic semiconductors include PEDOT:PSS, which was used as a anode in combination with other p-type polymers. Some of the heterojunction diodes also contain an electron blocking polymer sandwiched between the p-type polymer and the n-ZnO nano-wire. The insertion of electron blocking layer is necessary to engineer the device for the desired emission. Structural and electrical results will be presented. The preliminary I-V characteristics of the organic-inorganic hybrid heterojunction diodes show good rectifying properties. Finally we also present our findings on the origin of the green luminescence band which is responsible of the white light emission in ZnO is discussed.