Photoconductivity in organic semiconductors is very different from that in inorganic semiconductors. Optical absorption in organic semiconductors gives rise to excitons .The binding energy of the excitons is ~0.2-1 eV. Hence photoconductivity in organic sc requires the additional step of exciton dissociation. In this talk, I will use substituted carbazoles as an example to describe the mechanism of photoconduction in organic semiconductors. Using a simple model for transport, we estimate the mobility-lifetime product in these materials. We show that in favourable circumstances it is also possible to get information about microstructure from transport measurements. Finally we show that side groups influence the exciton binding energy in these materials. This should help in the design of new materials for organic PV.
Prof. Narasimhan has recently joined the Department of Electrical Engineering, IITB. He received his Ph.D. from the University of Bombay in 1977, since then he had been associated with TIFR. Prof. Narasimhan was the Chairman of the Department of Condensed Matter and Materials Science during Nov. 2002 to 2005. Prof. Narasimhan’s major research area is development of Organic semiconductors, porous silicon and Photovoltaics and has published more than 70 papers in these area.