Environmentally compatible 3-dimensional star-shaped donor materials for efficient organic solar cells

Small molecule (SM)-based star-shaped materials are getting tremendous attention to be employed as hole transport materials for organic/perovskite solar cells (OSCs) due to their tunable energy levels, intense absorption ability, and their three-dimensional (3D) charge transport properties. Herein, fourarmed SM donors (BD1-BD10) with benzodithiophene (BDT) as the centralcore unit have been efficiently designed and then characterized theoretically to investigate their optical and optoelectronic behavior. These four-armed designed star-shaped (BD1-BD10) materials exhibited deeper HOMO levels and higher extinction coefficients, which tend to offer better phase separation morphology during blend formation. These molecules (BD1-BD10) and reference (R) have been fully characterized theoretically with advanced quantum chemical approaches. The photophysical and optoelectronic characteristics have been investigated with density functional theory (DFT) and time-ependent (TD-DFT) calculations. The alignment of frontier molecular orbitals (FMOs), optical characteristics, open-circuit voltages, the density of states (DOS), transition density matrix (TDM), and reorganization energies of holes and electrons in these materials have been investigated. BD3 shows the highest absorption (lambda(max)) of 571.33 nm, with an optical bandgap at 3.30 eV, respectively. Moreover, a complex study of BD3/PC61BM unveiled the process of remarkable charge shifting at the donor-acceptor interface. Therefore, our proposed strategy is a prerequisite for designing desirable photovoltaic molecules for efficient organic/perovskite SCs and light-emitting diodes (LEDs).

Automated summary

Four-armed SM donors with benzodithiophene as the central core unit have been efficiently designed and characterized theoretically, showing deeper HOMO levels and higher extinction coefficients, leading to better phase separation morphology. Among them, BD3 exhibits the highest absorption at 571.33 nm and a significant charge shifting process at the donor-acceptor interface with PC61BM.