Design and Analysis of donor-acceptor-donor parts of Organic materials for Photovoltaic Cells

Abstract

The conversion of solar energy into electrical energy using photovoltaic cells is currently one of the most exciting research challenges. Organic photovoltaic (OPV) cells are in high demand for photovoltaic applications because of their mechanical flexibility, affordability, ease of production, and lightweight nature. The research has primarily focused on D-A-D (Donor-Acceptor-Donor) photovoltaic cells, extensively investigating the nature of Donor 1, Acceptor, and Donor 2 units. It has been observed that attaching carbon chains to both the Donor and Acceptor units can have positive effects on the efficiency of these organic photovoltaic material. The effect of carbon chain that bridges the D-A and A-D has not been investigated in literature. Therefore, in this research computational analysis was conducted on the organic materials for OPV utilizing quantum chemical calculations based on density functional theory (DFT) with the B3LYP hybrid functional and the 6-31G(d) basis set. The carbon chain length between donor-acceptor and acceptor-donor part of pristine organic materials was investigated for use in organic photovoltaic cells. A comprehensive investigation is performed to compare the relative energies, electronic characteristics, molecular orbital properties, absorption spectra, and photovoltaic qualities. According to the computed data, it has been observed that the relative energy increases with the addition of one or more methyl groups between the Donor-1 and Acceptor part or Acceptor and Donor-2 part of pristine molecule. The HOMO-LOMO of modeled structures has almost the same energy gap is ~0.22 eV like the pristine structure. The absorption data shows the increase in λ max with the addition of four carbon atoms but the photovoltaic properties, Voc (open-circuit voltage), is decreased from 0.60 to 0.51. It is concluded that the length of carbon chain length between the donor-acceptor and acceptor- donor units of D-A-D organic material has no significant impact on the efficiency of the photovoltaic cell.