Study of some organic polymeric materials for electrical and optoelectrical devices

In this paper, the electrical and optoelectrical properties of some polymer ic materials have been reported for their potential applications in photovo ltaic and organic light emitting diodes. The thin films of the organic poly mers were made over the indium tin oxide (ITO) coated glass substrates by s pin coating technique using suitable solvent. The metallic electrodes were deposited on the top of organic layer to make their respective sandwiched c onfiguration. Formation of schottky barrier and ohmic contacts in the devic es have been investigated by measuring the current - voltage (J-V) characte ristics in dark. Additionally, the comparison of the photoaction spectra of the devices with the optical spectra of the thin film layer or polymeric m aterials verify the nature of the contacts. The ohmic conduction and space charge limited current (SCLC) conduction either with single trap level or e xponential distribution of traps, have been discussed. One way to achieve higher energy conversion efficiency and carrier collecti on efficiency is to dope the polymers so that the efficient charge separati on occurs at the interface boundaries. It is found experimentally that dopi ng with appropriate dopants brings an adequate change in the optical and el ectrical properties of the organic materials. Chemical doping using accepto r type molecules with high electron affinity and donor type molecules with low ionisation energies reduces the electrical resistance as well as the th ermal activation energies and increases the photoconductivity. The doping w ith acceptor type molecules also increases the energy conversion efficiency .