Efficient tuning of benzocarbazole based small donor molecules with D-π-A-π-D configuration for high-efficiency solar cells via π-bridge manipulation: A DFT/ TD-DFT study

Abstract

Nine new donor molecules BCi (i = 1–9) of type D-π-A-π-D are explored to study their application to improve the efficiency of OSCs. These designed molecules contain a central diketopyrrolopyrrole acceptor linked to two terminal benzocarbazole donors by different π-bridges. Using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, various parameters like FMO, NBO, DOS analysis, absorption maxima, and ICT parameters have been estimated to evaluate the performance of newly designed molecules. Our investigations reveal that the modification of the π-bridges has a great effect on the optoelectronic and photovoltaic properties of the compounds. In this regard, it should be noted that the donor molecule BC6 with the π-spacer moiety thiazolothiazole exhibits a narrow band gap, a broad absorption spectrum, a better LHE, a lower values for λtot, ΔEL-L and chemical parameters, an acceptable Voc and a higher value of EA. Thus, they can be utilized as an electron-donating in photovoltaic applications.