Tuning the central donor core via intramolecular noncovalent interactions based on D(A-Ar)2 type small molecules for high performance organic solar cells

Abstract Two narrow band-gap small molecules with D(A-Ar) 2 framework, namely DMPh(DPP-Py) 2 and DFPh(DPP-Py) 2 , were designed and synthesized for high-performance small molecule organic solar cells (SMOSC), in which the 1,4-dimethoxybenzene (DMPh) and 1,4-difluorobenzene (DFPh) were employed as rigid donor cores, respectively, and the pyrenere (Py) unit is selected as terminal-capping groups on an electron-deficient diketopyrrolopyrrole (DPP)-based linear backbone. The impacts of the fluorine-sulfur (F⋯S) atoms and oxygen-sulfur (O⋯S) atoms noncovalent interaction on their absorption spectra, molecular energy levels, morphological properties, hole mobilities and photovoltaic properties were investigated thoroughly. The fluorinated DFPh(DPP-Py) 2 possess a relatively lower-lying HOMO energy level, better miscibility of the blend with PC 71 BM, as well as higher mobility in comparison with those of the methoxyled DMPh(DPP-Py) 2 . As a consequence, the OSCs devices based on DMPh(DPP-Py) 2 and DFPh(DPP-Py) 2 exhibited PCEs of 5.47% and 7.54%, respectively. Obviously, the device based on DFPh(DPP-Py) 2 presented a better performance, which should be ascribed to the improved simultaneously V oc of 0.77 V, J sc of 15.3 mA cm −2 , and FF of 64%. The results indicated that the choice of the fluorination designation on the molecular backbone is an effective approach to develop D(A-Ar) 2 type small molecule donors for highly efficient solar cell applications.