Designing new donor materials based on functionalized DCCnT with different electron‐donating groups: A density functional theory (DFT) and time dependent density functional theory (TDDFT)‐based study

Abstract

Finding a promising donor/acceptor material of organic solar cells is one of the most important ways to improve their power conversion efficiency. Extensive studies have focused on designing and synthesizing new and suitable materials. Small organic molecule materials, different from polymers, have many merits, such as easy synthesis and modification, less by‐products, and crystallinity. In the present work, we theoretically design a series of new donor materials based on 1‐(1,1‐dicyanomethylene)‐cyclohex‐2‐ene‐substituted oligothiophenes, that is, DCCnT (n = 1‐4) series. Furthermore, we model and predict photoelectric properties of functionalized DCCnT with different electron‐donating groups (─CH3/─CHCH2/─OCH3/─NH2/─OH). The calculated results, based on density functional theory and time‐dependent functional theory, show that DCCnT‐X (X = OH, NH2, and OCH3) series show odd‐even effect of dipole moments when n varies from 1 to 4, whereas DCCnT‐CH3 and DCCnT‐CHCH2 do not. Finally, we find that DCC3T‐X (X = OH, OCH3, and NH2) may be better candidates of donor materials because of their larger dipole moments, stronger electron donating ability, and smaller exciton binding energy with respect to prototype DCCnT molecules.

Designing Potential Donor Materials Based on DRCN5T with Halogen Substitutions: A DFT/TDDFT Study

“…Additionally, the value of HOMO of DRCN5T4Cl, DRCN5T6Cl, DRCN5T2Br, DRCN5T4Br, and DRCN5T6Br drops a lot, which results in a significant increase in their V OCS . The energy gaps of DRCN5T4Cl, DRCN5T6Cl, DRCN5T2Br, DRCN5T4Br, and DRCN5T6Br are higher than the others (DRCN5T2F, DRCN5T4F, DRCN5T6F, DRCN5T2Cl) by at least 0.3 eV, which may be mainly attributed to their non-planarity [25] (see Figure S1). In Figure S1, the selected dihedral angles ψ1 and ψ2 of DRCN5T4Cl, DRCN5T6Cl, DRCN5T2Br, DRCN5T4Br, and DRCN5T6Br are between 77 o and 90 o , indicating their strong non-planarity.…”

“…To take into account environment effects, we used integral equation formalism variant polarizable continuum models (IEF-PCM) [36,37]. In order to compare with experiments, the The oscillator strength of DRCN5T4Cl, DRCN5T6Cl, DRCN5T4Br, and DRCN5T6Br decreases significantly compared with that of DRCN5T (Figure 11), which might be caused by their reduced planarity [25]. The oscillator strength of DRCN5T2F, DRCN5T4F, DRCN5T6F, and DRCN5T2Cl increases in contrast to that of DRCN5T.…”