Design of donor-acceptor conjugated polymers for high-performance organic solar cells: a quantum mechanical approach

In this study, the design of donor-acceptor conjugated polymers for high-performance organic solar cells is intended by investigating electronic, geometrical and optical properties of a specific set of donors that are used in polymer solar cells. 4 different donors including benzo [1,2-b:4,5b'] dithiophene (BDT), 3,3'-difluoro-2,2'-bithiophene (diF2T), naphtho [1,2-b:5,6-b'] dithiophene (NDT), thieno[3,2-b] thiophene (TT) and 1 acceptor named 2-propyl-5,6-difluorobenzo[d][1,2,3]triazole (ffTAZ) are studied in order to set a benchmark. The 4 different donors studied for benchmarking and 7 different acceptors including benzo [c][1,2,5] thiadiazole (cop1), [1,2,5]thiadiazolo [3,4-g] quinoxaline (cop2), [1,2,5] thiadiazolo [3,4-d] pyri-dazine (cop3), [1,2,5]thiadiazolo [3,4-c] pyridine (cop4), [1,2,5] oxadiazolo [3,4-d] pyri-dazine (cop5), fluorinated naphtho [1,2-c:5,6c'] bis [1,2,5] thiadiazole (FNTz), fluori-nated [2,1,3] benzobisthiadiazole (FBTz) are combined and investigated for 28 different predictions. Geometrical and optical characteristics were calculated using Density Functional Theory (DFT). Distortion energies and reorganizational energies for electron and hole transfer were calculated using B3LYP/6-311G*. In conclusion, 2 out of 28 molecules were chosen as the most effective molecules to be used in high-performing organic solar cells. The molecules chosen contain NDT and TT as donors and FBTz as acceptor.