Preliminary photovoltaic response from a polymer containing p-vinylenephenylene amine backbone

Optoelectronic properties from a novel polymer, poly(p-phenylene N-4-n-butylphenyl-N,N-bis-4-vinylenephenylamine) (PNB) have been investigated. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the material were estimated to be -5.18 and -2.75eV, respectively, measured with cyclic voltammetry. A single-layer device structure was prepared by spin-coating PNB thin films from a solution on top of an indium-tin oxide (ITO) substrate while aluminum was used as a top electrode. Current density-voltage (J-V) characteristic was measured which showed a typical rectifying behavior. Photovoltaic from a single-layered device was observed under a white arc lamp illumination. This was improved via a double-layer structure comprising vacuum evaporated copper phthalocyanine (CuPc) or N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDT-C-13) as an additional layer. The open-circuit voltage, short-circuit current and hence the efficiency were improved in the double-layer devices. An ITO/PNB/PTCDI-C-13/Al device was estimated to have external quantum efficiency (EQE) around 1% at 330 nm. In a comparison of optical absorption and photocurrent spectra, it was demonstrated that the excitons could be separated and further, generated carriers drifting to the opposite electrodes more efficiently in the double-layer cells. (c) 2007 Elsevier B.V. All rights reserved.