Molecular Semiconductors : Charge Transport, Structural and Spectroscopic based Investigations

Conjugated polymers with delocalized -electron systems behave as model organic semiconductors. A broad programme of research on this topic exists in international laboratories by now. Activities range from design and synthesis of new polymers through to their use in a variety of devices and also to understand further insight of disordered semiconductor physics. My main interest is the semiconductor physics of these materials, which is very different from that of inorganic semiconductors and gives strong electro-optical and non-linear optical responses. A range of device-related projects I had carried out. (a) Field-effect devices (mobility reaching 20 cm2V-1s-1 for inkjet printed organic field effect transistors) show large changes in optical properties as a consequence of charge injection (b) Polymer light-emitting diodes (LEDs) were first made in Cambridge using poly(phenylene vinylene), and the performance of these LEDs - now has risen to surpass that of visible emitting inorganic devices. (c) Photovoltaic and photoconductive diodes can show high efficiency if heterojunctions between polymer layers are used to achieve charge separation, power conversion efficiency from these cells are approaching 10%. (d) Sub-picosecond time-resolved spectroscopy is used to study formation and evolution of polaronic electronic excitations. During this talk, I shall try to give you a broad overview of my research projects related to transport, structural and spectroscopy based investigations on molecular semiconductors with a brief introduction to this field.