Studies on Optoelectronic Properties of Polyaniline/Zinc Oxide <i>p</i>–<i>n</i> Heterojunction Diode

Polyaniline (PANI)-based heterojunction materials have promising application in optoelectronic devices. Herein, polyaniline(PANI)/zinc oxide (ZnO) p – n heterojunctions were constructed by a dip-coating method. X-ray diffraction (XRD) pattern showed diffraction peaks for PANI (2 θ = 25.6°) and ZnO (2 θ = 29.7° and 37.8°). The maximum dislocation density 5.2341 × 10 15 lines m −2 and strain (2.5431 × 10 −3 lines −2 m −4 ) were noted for PANI-salicylic acid (SA)/ZnO. Scanning electron microscopy (SEM) reveals the formation of PANI nanorods with ZnO nanoparticles. The average diameter and length of PANI nanotubes is ∼19 nm and ∼1 μ m respectively. Optical properties of PANI/ZnO heterojunctions were explored by photoluminescence(PL) and UV-visible absorption spectroscopy. Emission peaks were noticed at ∼430 and ∼470 nm. Absorption peaks for PANI were observed at 300, 450 and 600 nm, whereas lowest band gap of 3.17 eV was obtained for PANI-OA/ZnO. Functional groups and the interaction between PANI and ZnO particles were ascertained by Fourier transform infrared spectroscopy (FTIR). Effect of dopants on the optical, conductivity and optoelectronic properties were determined. The conductivity studies and the optoelectronic properties of these devices have been investigated via I-V characteristics. Low ideality factor ( n = 3.04) and very high barrier height (Φ b = 0.632, dark) was observed for PANI-oxalic acid (OA)/ZnO p–n heterojunction which will become a potential material in opto–electronic devices.