Effects of FeCl sub(3) as oxidizing agent on the conduction mechanisms in polypyrrole (PPy)/pc-ZnO hybrid heterojunctions grown by oxidative chemical vapor deposition

P-type polypyrrole (PPy) films are deposited on glass and on n-type polycrystalline ZnO (pc-ZnO) substrates by oxidative chemical vapor deposition under three different amounts of FeCl sub(3) used as oxidizing agents to form hybrid heterojunctions. Their microstructure, morphology, and electrical characteristics are studied. Particularly, current-voltage characteristics of the PPy/pc-ZnO heterojunctions are analyzed by defining an electrical equivalent circuit. The extracted parameters, together with the estimated heterojunction barrier height and the HOMO energy level of the PPy, indicate that a thermionic emission of holes at the heterojunction determines the saturation current of the diode at low voltage. For larger FeCl sub(3) amounts, the diode ideality factor increases indicating an increment of recombination by tunneling of charge carriers occurring at the heterojunction. This is attributed to a narrowing of the space charge region due to an increment of the number of charge carriers with a growing amount of FeCl sub(3). At high voltages, the PPy thickness influences the ohmic and space-charge limited current mechanisms at the bulk region. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1537-1544 Three different amounts of FeCl sub(3) are used as oxidizing agents to synthesize p-type polypyrrole (PPy) films on polycrystalline ZnO to fabricate hybrid p-n diodes by oCVD. Their electrical characteristics are analyzed with an electrical circuit model, a tool to understand physical phenomena in the devices. The amount of FeCl sub(3) has an impact on the morphology of the PPy and therefore on the conduction mechanisms occurring in the heterojunctions due to defect states.