Designing of 5,10-Dihydroindolo [3,2-b] Indole (DINI) Based Donor Materials for Small Molecule Organic Solar Cells

Abstract

In this paper, four small molecules B1, B2, B3 and B4 based on donor–acceptor–donor–acceptor–donor (D-A-D-A-D) combination were designed by making structural modifications in R. The designed molecules contain 5,10-dihydro-indolo [3,2-b] indole central donor core and different benzo-thiadiazole and fluorine substituted benzothiadiazole (FBT) acceptor units. These molecules have different subunits introduced on 5,10-dihydroindolo [3,2-b] indole central core like benzo [1,2,5] thiadiazole in (B1), 5-Fluoro-benzo [1,2,5] thiadiazole in (B2), 5-Methyl-benzo [1,2,5] thiadiazole in (B3), 2-Fluoro-2-methyl-2-H-benzotriazole unit in (B4), flanked with [2,2’,5’,2”] terthiophene as spacer (S) and triphenyl amine as a common end-capped donor in all the molecules (B1–B4). The optoelectronic properties of these molecules were studied by performing density functional theory (DFT) at CAM-B3LYP. Among all the designed structures, B2 showed maximum absorption (457[Formula: see text]nm) due to its strong electron withdrawing 5-Fluoro-benzo [1,2,5] thiadiazole acceptor unit. Other opto-electronic properties were analyzed through reorganization energies, density of electronic states and transition density matrix (TDM) to estimate the photovoltaic potential of these newly designed molecules. Low exciton binding energies and comparable values of open circuit voltage than R indicate the worth of these candidates to be used in future solar energy driven devices.

Theoretical framework for achieving high Voc in non-fused non-fullerene terthiophene-based end-capped modified derivatives for potential applications in organic photovoltaics

“…Smaller bandgap assists the phenomenon of charge transfer (CT). 62,63 The HOMO–LUMO bandgap can be calculated by using eqn (3). 64 E g = E LUMO − E HOMO …”

DFT insight of methoxy diphenylamine-substituted carbazole derivatives as hole transport material for efficient perovskite and organic solar cell

“…Additionally, a crucial element that directly affects a number of optoelectronic properties including electronic charge cloud, optical absorbance, excitation energy, and charge transport is the band gap (E g ) between HOMO and LUMO [44,45]. A common pattern is that molecules with a high band gap have low reactivity [46,47]. On the other side, molecules with smaller band gaps are soft, reactive, and have a fast rate of internal charge transfer [48,49].…”

Tuning of a A–A–D–A–A-Type Small Molecule with Benzodithiophene as a Central Core with Efficient Photovoltaic Properties for Organic Solar Cells

“…The energy difference between the LUMO and HOMO energy levels is called the band gap denoted as E g [ E g = E LUMO – E HOMO ]. The shorter the frontier orbital gap, the more the chemical reactivity, the lower the stability, and the easier the CT will be, thus the rate of CT increases that results in more photon utilization and an increase in the PCE . The band gap of the reference molecule SBDT-BDD is 4.49 eV.…”

“…λ ext. is ignored here, and the internal reorganization energy is calculated using eqs and of Marcus theory. , Hole and electron mobilities are calculated by estimating the energies of neutral, anionic, and cationic optimized geometries at DFT using CAM-B3LYP/6-31G­(d,p). Electron and hole reorganization values of all investigated molecules are tabulated in Table .…”

“…The shorter the frontier orbital gap, the more the chemical reactivity, the lower the stability, and the easier the CT will be, thus the rate of CT increases that results in more photon utilization and an increase in the PCE. 32 The band gap of the reference molecule SBDT-BDD is 4.49 eV. The band gap of all molecules is in the descending order of SBDT-BDD = SBDT4 > SBDT3 > SBDT2 > SBDT1.…”