Design and screening of B–N functionalized non-fullerene acceptors for organic solar cells via multiscale computation

Abstract

The molecular engineering of small molecule non-fullerene acceptors (NFAs) is central to enhancing organic solar cell (OSC) performance. One of the effective strategies is the chemical tailoring of the ladder-type central π-core unit of NFAs. Especially boron–nitrogen (B–N) functionalized heterocycles in ladder-type π-cores is considered a promising approach to boost the device performance by regulating energy levels, band gap, and photovoltaic properties of organic materials. Here, we employ a multiscale computational workflow to design acceptor–donor–acceptor (A–D–A) type B–N functionalized NFAs starting from well-defined building blocks representing the donor and acceptor units. Initial assessment of the dataset generated via quantum mechanical calculations revealed that B–N functionalization in the designed NFAs leads to a bathochromic shift in the absorption maximum in the near-infrared region with Δ_LUMO below 0.3 eV required for improved solar cell efficiency. Further, crucial threshold parameters are imposed on an initial database of 120 NFAs to screen and identify five potential candidate structures on which molecular dynamics simulations are performed to generate amorphous morphologies. Charge transport simulations on these morphologies exhibit ambipolar character with superior mobilities for holes and electrons compared to the parent molecule. Our design principle guides us in identifying novel NFAs with promising photovoltaic characteristics and highlights that precisely manipulating boron–nitrogen functionalization is a possible way toward high-efficiency OSCs.