Band Gap Engineering of a Ternary Copolymer Based on Polythiophene and Its Derivatives Using Genetic Algorithm

The electronic and conduction properties of a copolymer, based on polythiophene (PTP) and its derivatives: polyisothianaphthene (PITN) and polyisonaphthothiophene (PINTP), have been studied. The optimum percentages of the homopolymer units PTP, PITN and PINTP in the copolymer have been successfully obtained using Genetic algorithm (GA). In order to test the effectiveness of GA and also to substantiate the optimum solution in case of the present copolymer, a systematic search varying the block sizes of the constituent homopolymer units has been done. It has been found that increasing the block size of all the three components simultaneously, decreases the band gap of the copolymer. Also, it is seen that the band gap values become constant after block size of 20 for the three components and do not reach the band gap of the optimum solution obtained from GA. By varying the block sizes, the trends obtained for electronic properties validate that the solution obtained from GA is an optimum solution.