Photo-induced inter-chain and interfacial charge transfer in Cu–ZnO/ poly (3-octylthiophene) hybrid nanocomposites

Abstract Poly (3-octylthiophene) conducting polymer and Cu-doped zinc oxide hybrid nanocomposites films were prepared by using ultrasonication cast technique. The films were characterized using various characterization techniques for their structral, vibrational, morphological, and optical properties. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) investigations suggest the presence of ZnO nanoparticles in the polymer host matrix. FTIR measurements also confirm the presence of various functional groups in the thiophene ring of poly (3-octylthipohene) polymer as well as in its nanocomposites. The UV–visible absorption spectra of polymer films exhibit the broad range absorption covering the almost whole visible region and attributed to the generation of a high density of photo-induced charge carrier by the absorption of incident photons. This is an inherent process of the polymer that appears during the absorption of the incident photons leading to the separation of bound polaron pairs that present on adjacent polymer chains as a result of inter-chain charge transfer. However, broadening in the absorption spectra of polymer is observed by incorporating Cu–ZnO nanoparticles into the polymer host matrix. This is attributed to the fact that inter-chain as well as interfacial charge transfer are responsible for photo-induced charge carriers generation; and thus it increases upon increasing in the weight percentage of nanoparticles in the polymer host matrix. The processes of inter-chain and interfacial charge transfer are well explained by developing a schematic charge transfer diagram. Furthermore, the PL emission spectra of polymer film exhibit the characteristic peaks related to the aromatic benzene ring and formed chains between the benzene ring with quinone segments of polymer. However, the PL spectra of hybrid nanocomposites film show a dramatic decrease in the intensity of emission leading the quenching effect and attributed to the high recombination rate of generated charge carriers through the Cu–ZnO induced extrinsic non-radiative recombination centers such as trap and defects. Thus, poly (3-octylthiophene) and its hybrid nanocomposite films could be considered as potential material for solar cells, diode, light emitting diodes, and resistive switching memory devices.