The group research focus is in the development of high performance solution processable organic semiconductor materials for application in organic field effect transistors (OFET) and organic photovoltaic (OPV) devices. This work encompasses the design and development of organic semiconducting polymers and small molecules, as well as the materials science aspects of thin film formation and electrical performance.
Novel organic conjugated aromatic thienothiophene polymers and control of their alignment and organization in the liquid crystalline phase is a particular area of current emphasis. This work aims to contribute to a better understanding of the relationships between molecular self assembly and charge transport properties, resulting in these materials recently demonstrating very high charge carrier mobility in a solution processed OFET polymer device. These high values demonstrate that organic materials can be fabricated by solution methods, and still achieve performance comparable to amorphous silicon transistors.
In collaboration with colleagues within both the Physics and Chemistry Departments at Imperial College, work is now underway to develop new light absorbing polymers for bulk heterojunction solar cell devices, focusing on low bandgap, deep lying energy level materials with good charge transport and optimal charge separation.
Figure 1. (a) Representation of the long range organization of a thienothiophene polymer where the red bars represent the pi-stacked polymer backbones, and the red lines depict the interdigitated alkyl side chains; (b) DSC graph illustrating the multiple phase transitions; (c). AFM images of annealed films. Scale bar corresponds to 200 nm (courtesy of R.J. Kline, NIST) ; (d) Two-dimensional x-ray scattering at grazing incidence of an annealed film of PBTTT C12 (courtesy of M. Chabinyc, PARC).