Studies on the optical and electrical properties of poly(4-vinyl pyridine)/CuPc composite doped with iodine

Optical and electrical properties of Cu–phthalocyanine (CuPc) microparticle dispersed poly(4-vinyl pyridine) (P4VP) films have been studied. Optical micrographs of these composites reveal homogeneous dispersion of CuPc in P4VP. There is a change in optical spectrum due to weak bonding of phthalimide units with basic pyridine groups. The conductivity increases by 3–4 orders of magnitude depending on the percentage of CuPc. I/V study shows that there is non-Ohmic dependence of current at low field but turns to Ohmic at high field region. On increasing temperature, thermally generated carriers cause Ohmic conduction even at low field. On further doping with I2, the conductivity is found to increase by 5–6 orders of magnitude. For I2 doped composite, UV-Vis spectrum shows substantial decrease in the intensity of broad peak (600–700 nm) of CuPc revealing complete absorption of Pc moieties by I2. From I/V characteristics, it is found that the conduction is Ohmic in the low-field region and space charge limited current (SCLC) type at high field and high temperature. Thermal activation of large number of carriers gives large increase in current conduction.