Advancing heteroatom-enhanced A-DA’D-A pentacyclic small molecule-based acceptors to improve the optoelectronic characteristics for organic photovoltaics

Abstract

Heteroatom side-chain engineering of small-molecule-based (SMs) non-fullerene acceptors (NFAs) is considered a promising material in fabricating high-efficiency organic solar cells (OSCs). The SMs-based NFAs can potentially enhance optical and photovoltaic performances, speeding up the advancement in fabricating efficient OSCs. Here, we proficiently designed eight highly conjugated A−D−A−D−A molecules (AYU-1 to AYU-8). An in-depth study has investigated the structure-property relationship and the impact of heteroatom side-chain engineering. We performed advanced quantum chemical simulations employing density functional theory (DFT) and time-dependent (DFT) methods to examine the structural, quantum mechanical, and chemical parameters. Furthermore, we deeply investigated the hidden potential of this designed AYU-1 to AYU-8 series and synthetic reference molecule AYU-R. For this, we intensively explored the frontier molecular orbitals, binding and excitation energies, reorganization energies, transition density matrix, the density of states, and light harvesting efficiency analysis have been performed. Moreover, we also estimated the optical, optoelectronics, and photovoltaic properties of AYU-R and the designed AYU-1 to AYU-8 series. The optical analysis revealed that the designed series exhibited a bathochromic shift and is highly red-shifted in absorption maxima λ_max (688.95–795.69 nm) with a reduced optical bandgap of (1.91–1.99 eV) as compared to the AYU-R (2.09 eV). Furthermore, the charge transfer analysis of AYU-2:PTB7-Th presented a significant charge shifting at the HOMO (AYU-2) to LUMO (PTB7-Th) interface. Interestingly, the developed series (AYU-1 to AYU-8) demonstrated a superior optoelectronic performance than our reference compound, AYU-R.