Synthesis And Photovoltaic Properties Of The Thienyl Benzothiadiazole Organic Small-molecule And Copolymers Donor Materials

In this dissertation, the research progress of the materials and devices based on polymer solar cells and organic small molecule bulk heterojunction solar cells (BHJ) were sumarized systematically. In order to augment the charge carrier mobility of photovoltaic materials, we had synthesized a series of dithiophene-benzothiadia-zole-alt-fluorene copolymers by incorporating carbazole units into fluorene moiety and three organic small-molecule donor materials. The structures of these copolymers and small molecules were established by 1H NMR and Elemental analyses. The photophysical, thermal stability, electrochemical and photovoltaic properties of the copolymers and small molecules had been investigated by UV-vis spectra (UV-vis), the differential scanning calorimetry (DSC) , thermogravimetric analysis (TGA) and Cyclic Voltammetry (CV). Additionally, the photovoltaic performances of BHJ cells based on these copolymers and small molecules were fabricated. The main conclusions obtained in this paper are as follows:1. Three new conjugated copolymers PFO-FCz-DBT5,PFO-FCz-DBT15 and PFO- FCz-DBT30 and three organic small molecules photovoltaic materials D1,D2 and D3 based on aryl pyrrolo pyrrole-dione (DPP) and benzothiadiazole (BT) of 3D-2A and 2D-3A linear structure had been synthesized. The effect of carbazole units on the thermal, optical, electrochemical and photovoltaic properties had been investigated. The study consequences proved that carbazole groups could increase the charge carrier mobility of photovoltaic materials. Organic solar cells were made-up based on the blend of the copolymers and PC60BM at a weight ratio of 1:3. Under the simulated sunlight illumination of AM 1.5, 100 mW/cm², the power conversion efficiencies (PCE) for PFO-FCz-DBT5,PFO-FCz-DBT15 and PFO-FCz-DBT30 are 0.52%,1.11% and 2.41%, respectively.2. Three organic small-molecules photovoltaic materials ( D1,D2 and D3 ) based on aryl pyrrolo pyrroledione (DPP) and benzothiadiazole (BT) of 3D-2A and 2D-3A linear structure had been synthesized by Stille coupling,Suzuki coupling and Knoevenagel condensation. The effect of carbazole units on the thermal, optical, electro-chemical and photovoltaic properties had been investigated. This work demonstrated that introducing a hole-transporting carbazole unit into small-molecule could improve the J_sc and PCE. BHJ cells were fabricated based on the blend of the as-synthesized small-molecule and PC60BM at a weight ratio of 1:4. Under the simulated sunlight illumination of AM 1.5, 100 mW/cm², D1 showed the best PCE of: 0.39% (J_sc= 2.56 mA/cm², V_oc = 0.54 V, and FF = 0.28).