Designing Benzodithiophene‐Based Donor Materials with Favorable Photovoltaic Parameters for Bulk Heterojunction Organic Solar Cells

Abstract

AbstractComputational study on four Acceptor‐Donor‐Acceptor (A–D‐A) type of donor molecules namely, dimethyl cyanoacetate terthiophene di(methylthiophene) benzo[1,2‐b:4,5‐b′]dithiophene (DMCATDMTBDT) (M1), methylrhodanine terthiophene di (methylthiophene) benzo[1,2‐b:4,5‐b′]dithiophene (MRTDMTBDT) (M2), dimethyl cyanoacetate terthiophene di (fluoromethyl thiophene) benzo[1,2‐b:4,5‐b′]dithiophene (DMCATDFMTBDT) (M3), and methylrhodanine terthiophene di (fluoromethyl thiophene) benzo[1,2‐b:4,5‐b′]dithiophene (MRTDFMTBDT) (M4) was carried out and their photovoltaic properties were associated with methyl cyanoacetate terthiophene di (methoxy) benzo[1,2‐b:4,5‐b′]dithiophene (DCAO3TBDT) (R1) and methylrhodanine terthiophene di (methoxy) benzo[1,2‐b:4,5‐b′]dithiophene (DR3TBDT) (R2). For the geometry optimization DFT functional CAM−B3LYP/6‐31G (d) was found to be the best choice, hence TD‐CAM−B3LYP/6‐31G (d) was opted for the calculation of excited state of the molecules. M3 and M4 represented appropriate frontier molecular orbital energy levels and broad absorption band. The reorganization energies of the designed molecules illustrated excellent charge mobility property. The lower λe values as compared to λh illustrate that the designed donor molecules are better electron donors. M4 was found as champion molecules with the lowest λe (0.01601) value. The Voc value of M3 and M4 are 2.74 eV and 2.63 eV respectively with respect to the energy levels of PC60BM (acceptor).