Charge transport in polythiophene molecular device: DFT analysis.

We report the charge transport phenomenon in polythiophene molecular device and the ways of controlling the nature of charge transport through the device. By using density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalisms, two ways of controlling the nature of charge transport have successfully been demonstrated by introducing conformational changes in the channel and applying external gate potential. Functional groups with negative mesomeric effect such as nitrous and carboxyl and positive mesomeric effect such as amino have been used as substituents as part of introducing conformational changes in the channel. The results indicate that the nature of charge transport in polythiophene molecular device can be changed from hole dominant to electron dominant and vice versa just by introducing minor conformational changes in the channel and by changing the polarity of external gate potential. Moreover, the negative differential resistance (NDR) behavior has been observed in amino-substituted thiophene device. These findings will be very useful in understanding the design of both p and n-type transistors out of same molecule for the next-generation molecular electronics.