Effect of fluorine on optoelectronic properties in DI-A-DII-A-DI type organic molecules: A combined experimental and DFT study

The impact of the substitution of fluorine atom/atoms on the optoelectronic features of organic molecules having D-I-A-D-II-A-D-I type architecture is examined in the current work. The three synthesized organic molecules (SMD1, SMD2 and SMD3) comprise of a dithienopyrrole (DTP) derivative as a central donor (D-II), which is flanked between two benzothiadiazole (BT) moieties (electron acceptors, A). The BT core on each of two ends is joined to an electron-donating benzodithiophene (BDT) derivative (D-I). The SMD1, SMD2 and SMD3 are substituted with 0, 2 and 4 fluorine atoms on their BT moiety respectively. The assistance of DFT methods is taken to evaluate the influence of fluorine on reorganization energies, ionizing potential and electron affinity of molecules. The thermal stability of molecules is mapped by TGA studies. Cyclic voltammetry studies are carried out to comprehend the characteristics of highest molecular orbital, lowest unoccupied molecular orbital and the bandgap of molecules, which are also supported by DFT methods. The molecules displayed better absorption properties in the near-infrared (NIR) region, excellent solution processability in a variety of organic solvents, low bandgap and optimum thermal toughness to make them applicable in the construction of OBHJSCs to play the role of donor materials when connected with acceptors like fullerene derivatives. (C) 2020 Elsevier B.V. All rights reserved.