Synthesis And Properties Of A-D-A-type Organic Small Molecular Photovoltaic Materials

Solution-processable bulk-heterojunction organic solar cells have attracted great attentions due to their advantages of portbale, flexible, easy-fabrication and large-scale manufacture potential. In order to carry the commercialization a step forward, the efficiencies for small molecular semiconductors need to be improved.In this paper, we reported the synthesis and photovoltaic properties of nine novel A-D-A-type small molecule donor materials, CZ(TDPP)2, DPA(TDPP)2, PTZ(TDPP)2, FL(TDPP)2, LCZ(TDPP)2, CZ(TBT)2, CZ(NCT)2, CZ(ETDPP)2and DPA(ETDPP)2, which contain diketopyrrolopyrrole, benzothiadiazole or nitryl as acceptor and carbazole, diphenylamine, phenothiazine or fluorine as donor. In order to investigate their photophysical and electrochemical properties, the Density Functional Theory (DFT) calculations, UV-Vis absorbance, cyclic voltammetry and fluorescence quenching experiment were carried out, meanwhile fabricating the BHJ solar cells based on these new materials as donor and PC61BM as acceptor.With the performance of the synthesized materials, we research the influence of various electron-donating and electron-withdrawing units on the photoelectricity properties, and get the following main conclusions:1) CZ(TDPP)2owned the higher PCE due to more coplanar structure and more π-electron delocalized.2) The incorporation of DPP unit into the A-D-A-type small molecules could guarantee the materials harvest sunlight at whole visible spectrum range.3) Employing the C C as the bridge could lower the highest occupied molecular orbit (HOMO) of donors to increase the open-circuit voltage.