Synthesis And Properties Of Asymmetric Organic Photovoltaic Materials Based On Quinoxaline

The organic small molecule photovoltaic donor materials have the advantages of low cost,simple synthesis,easily modified structure,good repeatability and so on.It has been developed rapidly in recent years,and the efficiency of single junge device has already exceeded 11%.Quinoxaline?Qx?is a good electron-withdrawing group,and it can be coupled with electron-donating unit to form narrow band-gap compounds.However,organic small molecules photovoltaic donor materials based on Qx unit have few studies especially asymmetric Qx-based small molecules materials.Therefore,this paper has designed and synthesized two series of D-A₁-A₂ type organic small molecules,which consisting of Qx and alkoxy-substituted Qx as central electron-withdrawing moiety?A₁?;triphenylamine?TPA?as electron-donating unit?D?;and different group-substituted benzenes as terminal electron-withdrawing group?A₂?.The sythesized molecules were characterized by nuclear magnetic resonance spectrum and high resolution mass spectrometry.Then theoretical calculation was carried out to understand energy level and electronic distribution,and the optical and electrochemical properties of the materials were studied by UV-visible absorption and cyclic voltammetry.Finally,synthesized molecules were used as donor materials and fullerene derivative(PC₆₁BM)as acceptor material to fabricate bulk heterojunction devices,and conducted their photovoltaic?PV?performance.Besides,the solvent evapor annealing?SVA?was performed to optimize active layer in order to further enhance their PV.The results showed that:?1?the introduction of alkyl and alkoxyl chain could enhance molecular solubility;?2?different electron-deficient end-groups have less influence on the PV performance;?3?Compounds TPACNQx CN,TPACNQxF₂ and TPACNOQxCN obtained high voltage of 1.00 V,1.11 V and 1.03 V respectively;?4?the SVA process can significantly improve J_sc and FF,which made the Power Conversion Efficiency?PCE?significantly improvement.The result shows that the effect of the end group on the photovoltaic data is very small,but the low HOMO level of Qx is more beneficial to obtain a higher Voc,which provides a reference for the design of high voltage materials.