A Density Functional Theory Study of Side Chains Effects on the Intermolecular Interactions and Electronic Structures of Small Molecular Acceptors for Organic Photovoltaics

Abstract

Diketopyrolopyrole‐thiophene‐phenyl (DPPT‐Ph)‐based small acceptor molecules for organic photovoltaics application were investigated at density functional theory (DFT) level using ω B97X‐D functional and 6‐31G(d) basis sets: Acceptor molecules include DPPT‐Ph and its cyanide analogs, o‐, m‐, and p‐DPPT‐PhCN molecules with either methyl or 2‐ethylhexyl groups attached on DPP unit. With methyl side chains, acceptor molecules form π‐stacked dimers, i.e., syn‐ and anti‐cofacial configurations. Strong π–π interactions between backbone of acceptor molecules in such dimers, however, turned out not to alter absorption spectra dramatically with respect to those of single molecule due to the negligible intensity of peaks pointing to the lowest‐lying excited states. On the other hand, the disruption of π–π interactions induced by the presence of side chains, albeit alleviates peak‐splitting, notably intensifies such peaks at the cost of intensity reduction of the most prominent neighboring peak. Our results place significant emphasis on the importance of the manipulation of side chain to improve the device performance of organic photovoltaics.

Rational design of the S,N‐heteroacene‐based nonfullerene by introducing the fluorine atom for efficient high‐performance organic solar cells

“…First, it shows a strong electronegativity of the substituted sites and it can improve intermolecular interaction through internal F-S and F-H noncovalent interaction promoting charge transport. 16,17 Meanwhile, the F atom continuously leads to a change in the molecular interaction and the morphology. Second, it can obtain the more redshifted absorption and deep energy level.…”

“…The roles of F atom‐functionalized materials have been well studied. First, it shows a strong electronegativity of the substituted sites and it can improve intermolecular interaction through internal F–S and F–H noncovalent interaction promoting charge transport 16,17 . Meanwhile, the F atom continuously leads to a change in the molecular interaction and the morphology.…”