Designing small organic non-fullerene acceptor molecules with diflorobenzene or quinoline core and dithiophene donor moiety through density functional theory

Abstract

The non-fullerene acceptors A1–A5 with diflourobenzene or quinoline core (bridge) unit, donor cyclopenta[1,2-b:3,4-b′]dithiophene unit and 2-(2-methylene-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile as acceptor unit with additional phenyl, fulvene or thieno[3,2-d]pyrimidinyl 5-oxide groups have been designed through DFT calculations. The optimization of molecular geometries were performed with density functional theory (DFT) at B3LYP 6-31G (d,p) level of theory. The frontier molecular orbital (FMO) energies, band gap energies and dipole moments (ground and excited state) have been calculated to probe the photovoltaic properties. The band gap (1.42–2.01 eV) and dipole moment values (5.5–18. Debye) showed that these designed acceptors are good candidates for organic solar cells. Time-Dependent Density Functional Theory (TD-DFT) results showed λmax (wave length at maximum absorption) value (611–837 nm), oscillator strength (f) and excitation energies (1.50–2.02 eV) in gas phase and in CHCl3 solvent (1.48–1.89 eV) using integral equation formalism variant (IEFPCM) model. The λmax in CHCl3 showed marginal red shift for all designed acceptors compared with gas phase absorption. The partial density of states (PDOS) has been plotted by using multiwfn which showed that all the designed molecules have more electronic distribution at the donor moiety and lowest at the central bridge. The reorganization energies of electron (λe) (0.0007 eV to 0.017 eV), and the hole reorganization energy values (0.0003 eV to − 0.0403 eV) were smaller which suggested that higher charged motilities. The blends of acceptors A1–A5 with donor polymer D1 provided open circuit voltage (Voc) and ∆HOMO off-set of the HOMO of donor and acceptors. These blends showed 1.04 to 1.5 eV values of Voc and 0 to 0.38 eV ∆HOMO off set values of the donor–acceptor bends which indicate improved performance of the cell. Finally, the blend of D1–A4 was used for the study of distribution of HOMO and LUMO. The HOMO were found distributed on the donor polymer (D1) while the A4 acceptor was found with LUMO distribution. Based on λmax values, and band gap energies (Eg), excitation energies (Ex), reorganization energies; the A3 and A4 will prove good acceptor molecules for the development of organic solar cells.

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

“…The greater the dipole moment, the larger the charge separation and enhances the solubility in polar solvents accompanied by better crystallinity of molecule. 73 However, it is inversely linked to the symmetry of molecules. Polar solvents increase the dipole moment of organic compounds, and larger dipole moments result in higher charge mobilities.…”

Organic Field Effect Transistors Comprising Copolymers Synthesized without Structure-Directing Moieties with Enhanced Carrier Mobility

“…The LUMO wavefunction was distributed over BODIPY and i -indigo in the case of P1 and BODIPY and thieno- i -indigo in the case of P2 (Figure ). Usually, the LUMO wavefunction is centered on the i -indigo unit when it was connected with donor moieties . In those cases, the donor is electron rich.…”

“…Usually, the LUMO wavefunction is centered on the i-indigo unit when it was connected with donor moieties. 49 In those cases, the donor is electron rich. Contrary to them, the donor (BODIPY) in P1 and P2 are not electron rich.…”

Theoretical studies on donor–acceptor based macrocycles for organic solar cell applications

“…Therefore, both hole and electron reorganization energies (λ + and λ − ) were calculated by using the following Eqs. ( 3 ) and ( 4 ) 47 . …”