Three diketopyrrolopyrrole-thiophene-based small molecules were synthesized substituting electron-withdrawing cyanide group in different positions and introduced as acceptors in organic photovoltaic cells.

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.