PERFORMANCE COMPARISON OF p–n JUNCTION DIODES USING ZINC OXIDE AND COPPER PHTHALOCYANINE HYBRID NANOCOMPOSITES AND BILAYER HETEROSTRUCTURES

Abstract

Nanocomposites of n-type Zinc Oxide ( ZnO ) and p-type copper phthalocyanine ( CuPc ) were synthesized using solution route and the electrical properties of heterojunctions of ZnO and CuPc in the nanocomposite film was studied. For comparison, electrical properties of bilayer heterojunction devices using ZnO nanostructure drop cast film and thermally evaporated CuPc were also studied. Rectification ratio (RR) of about 28 and 5.5 was obtained at 4 V for devices with nanocomposite film and bilayer heterojunctions indicating improved formation of p–n junction characteristics for nanocomposite films. Values of ideality factor, barrier height at the p–n junction interface and series resistance were estimated using different methods like semilog plots, Cheung and Norde's methods. Ideality factor estimated from semilog plots and Cheung's methods were found to be higher than unity indicating deviation from ideal diode behavior. Barrier height estimated from different methods was about 0.7 eV. Series resistance measured using Cheung and Norde's methods were found to be about 92 KΩ and 21 KΩ, respectively. Bilayer heterojunction devices exhibited much higher series resistance, ideality factor and barrier height as estimated using all the above-mentioned methods as compared to the devices with nanocomposite film. The above results indicate intimate mixing and improved interface between ZnO and CuPc in the in situ synthesized nanocomposite film thereby offering improved p–n junction characteristics.