The Design And Synthesis Of Diketopyrrolopyrrole-containing Small Molecule Materials For Organic Photovoltaics

Soluble small molecules are emerging as a competitive candidate to donor materials in solution-processed organic solar cells (OSCs) due to some promising advantages, including well-defined structure thus less batch-to-batch variation, good solubility, and easier to purify compared with polymers. We focus on extend the absorption and improve the energy levels, thus enhance the power conversion efficiencies by molecular design. In this thesis, diketopyrrolopyrrole(DPP) dyes as the main building blocks in company with other donor and acceptor groups were introduced into donor-acceptor small molecules. The relationship between molecular structure and absorption as well as energy levels were systematically investigated.Four linear (DPP-BT、DPP-TZ、TPA-DPP-3T、TPA-DPP-BDT) and one star (S(TPA-DPP)) donor-acceptor molecules were synthesized through Pd(0) catalysed Suzuki and stille cross-coupling reaction. All new compounds were characterized with NMR and high-resolution matrix-assisted laser desorption ionization (MALDI) mass spectra.The optical and redox properties of all five compounds were investigated. All compounds showed a broad absorption from the uv and visible spectra. The larger red shift of the absorption in solid state relative to that in solution indicates an effective π-π packing between the molecule backbones at the solid state. In addition, the molecule backbones of cmpound DPP-TZ and TPA-DPP-BDT is the largest. The diboron esters of Oligothiophene (3T), benzodithiophene(DBT) can also be synthesized to get compound TPA-DPP-3T. TPA-DPP-BDT according to the reported procedures. The larger red shift of the absorption in solution state relative to compound TPA-DPP. Compound TPA-DPP containing thiophene,2,2’-bithiophene, fluorine,2,1,3-benzothiadiazole (BT) performs a larger red shift compares to cmpound DPP-TZ which contains thiazolo[5,4-d]thiazole. Star (S(TPA-DPP)) molecules performs a larger red shift and the reduction of the molecular orbital level attributed to the aldehyde group relative to compound that was reported. According to the redox properties of these compounds, the molecular energy level(HOMO/LUMO) can be systematically tuned by changing the struction of the moleculars. These compounds has prospect future in organic solar cells considering to the absorption spectrum and the molecular energy level.