Abstract
We report low-temperature solution-processed p-CuO nanorods (NRs)/n-ZnO NRs heterojunction light emitting diode (LED), exploiting the native point defects of ZnO NRs. ZnO NRs were synthesized at 90 °C by using hydrothermal method while CuO NRs were synthesized at 100 °C by using microwave reaction system. The electrical properties of newly synthesized CuO NRs revealed a promising p-type nature with a hole concentration of 9.64 × 1018 cm−3. The current-voltage characteristic of the heterojunction showed a significantly high rectification ratio of 105 at 4 V with a stable current flow. A broad orange-red emission was obtained from the forward biased LED with a major peak at 610 nm which was attributed to the electron transition from interstitial zinc to interstitial oxygen point defects in ZnO. A minor shoulder peak was also observed at 710 nm, corresponding to red emission which was ascribed to the transition from conduction band of ZnO to oxygen vacancies in ZnO lattice. This study demonstrates a significant progress toward oxide materials based, defect-induced light emitting device with low-cost, low-temperature methods.
Highlights
Orange-red light emission from the device was observed in the naked eye
The PL spectra of ZnO NRs revealed that it contains a large number of defect states, resulting in a broad and intense deep level emission
Undoped ZnO NRs were grown onto the patterned Ga-doped ZnO (GZO)-coated substrate in 50 ml of aqueous solution containing 297.49 mg of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) and 140.19 mg of hexamethylenetetramine (HMT) at a temperature of 90 °C for 1 h34–36
Summary
Materials syntheses and characterization.Prior to grow ZnO NRs, 3 wt% Ga-doped ZnO (GZO) was deposited on glass and GZO-coated glass was used as the substrate. We have transferred a circle pattern of 5 μ m diameter on the substrates by using optical lithographic technique to achieve continuous, compact, and uniform ZnO NRs. Undoped ZnO NRs were grown onto the patterned GZO-coated substrate in 50 ml of aqueous solution containing 297.49 mg of zinc nitrate hexahydrate (Zn(NO3)2.6H2O) and 140.19 mg of hexamethylenetetramine (HMT) at a temperature of 90 °C for 1 h34–36. CuO NRs were synthesized using a facile low-temperature solution method in CEM’s MARS 6 microwave reaction system. After the completion of reaction, the resulting solution was centrifuged and washed in DI water and ethanol, consecutively. The structural property of CuO NRs was characterized by using JEOL’s JEM-ARM 200F transmission electron microscopy (TEM). The electrical properties of CuO NRs were investigated by room temperature Hall measurements in van der Pauw configuration
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