Improving optoelectronic and charge transport properties of D-π-D type diketopyrrolopyrrole-pyrene derivatives as multifunctional materials for organic solar cell applications.

A series of novel diketopyrrolopyrrole-pyrene-based molecules were designed for small molecule based organic solar cell (SMOSC) applications. Their electronic and charge transfer properties were investigated by applying the PBE0/6-31G(d,p) method. The absorption spectra were simulated using the TD-PBE0/6-31G(d,p) method. The results showed that the frontier molecular orbital (FMO) energy levels, reorganization energy, the energetic driving force, and absorption spectra can be tuned by the introduction of different aromatic heterocyclic groups to the side of diketopyrrolopyrrole fragments' backbones. Additionally, the designed molecules possess suitable FMOs to match those of typical acceptors PCBM and PCBM. Meanwhile, the designed molecules can act as good ambipolar charge transport materials in SMOSC applications. Meanwhile, the electron and hole reorganization energies of the designed molecules are smaller than those of the typical electron and hole transport materials, respectively. Moreover, the differences between electron and hole reorganization energies do not exceed 0.046 eV. Our results suggest that the designed molecules can act as promising candidates for donor and ambipolar charge transport materials in SMOSC applications.