Designing of U-shaped acceptor molecules for indoor and outdoor organic solar cell applications

Efficient molecular modeling approaches draw great attention from the scientific community to further boost the photovoltaic performances of the solar cell's materials. For this purpose, various end-capped and bridged-core modifications have been carried out to construct a suitable molecule best fitted for solar cell applications. Herein, we have designed a small-molecule-based fullerene-free acceptor materials (IOD1-IOD7) for organic solar cells (OSCs) by doing end-capped modifications and characterized them theoretically by employing various quantum chemical density functional theory (DFT) and time-dependent (DFT) approaches. Designed molecules IOD1-IOD7 disclosed narrow band gap (E-g = 2.104 to 2.194 eV) as compared to reference molecule (2.197 eV). Further, red shifting in absorption spectrum of designed molecules (lambda(max) = 751 to 771 nm) is noted as compared to reference molecule (lambda(max) = 749 nm), which suggested that designed molecules are efficient near infrared light absorber. Low reorganizational energy of electron in designed molecules (lambda(e) = 0.0159 to 0.0189 E-h) offers high charge mobility as compared to reference molecule. Low excitation energies (E-x = 2.10 to 2.43 eV) and low binding energies (E-b = 0.034 to 0.084 eV) are noted in designed molecules as compared to reference molecule (E-x = 2.56 eV and E-b = 0.087 eV) which demonstrated that designed molecules are better candidates for high-performance organic solar cells. Open-circuit voltages (V-oc) values, electronic structures, frontier molecular orbitals, and charge transfer phenomenon have also been studied theoretically. The outcomes of these theoretical characterizations revealed that all the newly designed non-fullerene acceptor materials exhibit a wide-ranging absorption efficiency and exciton dissociation constant values, with quite lower LUMO energy level, ensuring a boost in various photo-physical and in optoelectronic properties of the designed materials, which will eventually improve the power conversion efficiency (PCE) of the OSCs devices.

Automated summary

Efficient molecular modeling approaches have been used to design small-molecule-based fullerene-free acceptor materials with narrow band gaps, red shifted absorption spectra, and low reorganizational energy of electrons, making them promising candidates for high-performance organic solar cells.