Synthesis And Photovoltaic Properties Of D-A-D Type Organic Photovoltaic Materials Based On Isoindigo And Diketopyrrolopyrrole

Compared with other application of new energy, organic solar cells(OSCs) has the advantage of low cost, light quality and so on. Therefor the OSCs has been an important field of the new energy development. The developing of OSCs and their donor materials are reviewed,in this dissertation, and for the existence of various probelm, such as a low efficiency of energy conversion are analyzed. Two series of organic small molecule containing electron acceptor isoindigo(IID) unit and electron donor pyrene(Py) unit or diketopyrrolopyrrole(DPP) acceptor unit and eletron donor carbazole(Cz) were designed and synthesized. The molecular structures of these organic intermediates and target compounds were characterized by 1H NMR and MALDI-TOF. The thermal stability, optical properties, electrochemical properties of target compounds were studied by thermogravimetric analyses, UV-vis absorption spectra, and cyclic voltammetry. Furthermore, the photovoltaic properties of organic small moleculs were investigated by bulk heterojunction solar cells with the organic small moleculs as donor materials. The main study results are listed below:1)A kind of the novel D-A-D type small molecules of IID(Py)2, IID(Ac–Py)2 and IID(Th–Py)2 were designed and synthesized, in which isoindigo(IID) unit is employed as acceptor(A) unit, and pyrene(Py) unit is used as donor(D) unit of D-A-D type small molecule material. Compared to IID(Py)2, IID(Ac–Py)2 and IID(Th–Py)2 with π-bridge(acetylene, thiophene), show a longer conjugated degrees,a wider absorption, lower HOMO energy level, which is beneficial to obtain a good photovoltaic performance. Under the optimized condition, bulk heterojunction organic solar cells(OSCs) based on IID(Th–Py)2 exhibited a better power conversion efficiency(PCE) of 1.01% with a short-circuit current(Jsc) of 4.1 mA/cm2 and a fill factor(FF) of 33.7%.2)A kind of the novel D-A-D type small molecules of DPP-C12-DCz,DPP-C16-DCz, DPP-C20-DCz were designed and synthesized, in which diketopyrrolopyrrole(DPP) unit is employed as acceptor(A) unit, and carbazole(Cz)unit is used as donor(D) unit. The length of alkyl side chain of DPP amide groups for small molecular photovoltaic performance were studied. Research shows that extending the alkyl side chain length can improve the solubility of the molecular, thus affecting device for receptors in the blend membrane surface morphology and phaseseparation degree, ultimately affectin their carrier mobility and PCE. Under the optimized condition, bulk heterojunction organic solar cells(OSCs) based on DPP-C16-DCz exhibited a better power conversion efficiency(PCE) of 1.19% with a short-circuit current(Jsc) of 5.09 mA/cm2, open circuit voltage(Voc) of 0.69 V and a fill factor(FF) of 33.76%.