Molecular engineering of the core part of D–π–A–π–D based small acceptor molecules for efficient organic solar cells: a DFT approach

Abstract

In this study, we have designed five new conjugated acceptors of donor–π–acceptor–π–donor (D–π–A–π–D) type, utilizing quinacridone as the donor and thiophene as the π-bridging component and incorporating five distinct central acceptor units. Our aim is to explore how different central acceptor units impact the geometric, electrical, optical, charge transport, and photovoltaic characteristics of these acceptor molecules. To achieve this, we have employed the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The results, including frontier molecular orbital analysis and several crucial parameters such as bond length alteration, the charge transfer rate, and power conversion efficiency, indicate that enhancing the electron-withdrawing characteristics of the central acceptor units boosts the performance of the designed acceptor molecules. The observed reorganization energy values confirm the electron-accepting nature of the compounds under study. Moreover, the absorption properties demonstrate that compounds C2 and C4 exhibit the highest maximum absorption values. Analysis of the D/A blend properties suggests that complexes A1/C2 and A1/C4 could facilitate efficient charge carrier separation within the D/A active layer. Furthermore, the photovoltaic performance of the D/A complexes indicates that complex A1/C2, with a predicted power conversion efficiency of 30.33%, stands out as the most promising candidate for use in organic solar cells.