Donor And Acceptor Material Based On DPP:Design、Synthesis And Performance

Diketopyrolopyrrole (DPP) is a kind of classical electron-deficient dye. Which was widely applied in polymer transistor materials and organic solar cell materials due to their good absorption and excellent solubility after modified by alkyl chains.There are a lot of studies about DPP based small-molecule donor material. So far, the max photoelectric conversion efficiency of these solar cells has been over 7%. The unit of DPP has low LOMO energy level and favorable absorption. In recent years, DPP used as an electron acceptor materials to replace fullerene which had widely attracted scientists’s attention.The reports about DPP used as a donor material had never been stoped from 2010 year. But their photoelectric conversion efficiency was not very satisfied. DPP molecule was highly planarity, and easy to crystallize, in the active layer tends to form crystals larger area which were disadvantages of the separation of excitons.Our team have done some preliminary work which DPP as an acceptor materials. In the year of 2015, we first reported small molecular DPP acceptor,whose central core is spirofluorene (SF). Among them, SF-DPPEH which modified by isooctyl, use P3HT as donor material. We make it into photovoltaic devices, its photoelectric conversion efficiency is up to 3.63%. Researches indicate that spirofluorene makes the whole molecular in a cross structure. On the one hand, it can properly inhibit the self-polymerization of DPP. On the other hand, two mutually perpendicular planes in the molecular can keep some crystallization, which is beneficial to improve the electron-transport of active layer. However, we further find that the absorption spectrum of SF-DPPEH has much overlap with P3HT, which doesn’t form complementation in absorption spectrum. We can forsee that, broadening absorption spectrum of SF-DPPEH, can make better complementation with P3HT and greatly improve the absorption spectrum of active layer, in order to increase the short-circuit (Jsc) of the device. Therefore, on the basis of SF-DPPEH with excellent property, we modify its terminus with benzene, trying to broaden its absorption spectrum and to improve crystallization.We further modified the DPP in the thiophene ring. DPPN, DPPBF, DPPBT which were modified by naphthalene, isobenzopyran and benzothiophene respectly. We then link the modified DPP with spirofluorene. AS the above-mentioned, the crossstructurecan effectively reduce its self-polymerization during the film formation. The DPP molecular modified by these three aromatic compounds can increase their conjugated structure, so as to broaden their absorption spectrum.Investigated by UV-vis spectra we found that compared with SF(DPPEH)4,the three molecular which were synthesized by new methods had more than 30nm absorbtion that consisted with our speculate. The SF(DPPN)4’s photoelectric conversion efficiency was 1.15%.In order to broaden the application of non-fullerene acceptor material, we have synthesized four DPP polymer receptor material. By UV absorption spectroscopy, we found that they had a good absorption at 300-400nm and 550-750nm. Blend with P3HT, made the whole polymer solar cell devices. The results of PV test showed that theirs highest performanceof PCE was 0.5%.In the meanwhile, in order to obtain three new polymer donor materials we also copolymerize DPP with classic pentathiophene which we’ve synthesized. Compared with small molecule, the polymer has better flexibility relative which can form better film when use it fabricate devices and have higher carrier mobility. From the above it can be seen that DPP have better Photovoltaic (PV) performance in both organic solar donor materials and acceptor materials. We need to study its performance deeply.