Synthesis And Photovoltaic Properties Of Polymer Donor Materials Based On Quinoxaline Derivatives

Polymer solar cells（PSCs）have been the focus of research in the field of organic solar cells（OSCs）due to their excellent properties such as light weight,flexibility,translucency and large-area roll-to-roll printing.In this paper,a systematic review of polymer donor materials is presented.In view of the few kinds of highly efficient polymer donor materials and the unclear relationship between molecular structure and properties,we have constructed three kinds of“D-A”type of polymer donor materials based on quinoxaline derivatives.The photophysical,electrochemical and thermal stability properties of these materials were investigated.Polymer solar cell（PSCs）devices based on fullerenes（FAs）or non-fullerenes electron acceptors（NFAs）were constructed.The better-performing polymer donor materials were screened to reveal the relationship between the molecular structure of polymer donor materials and their photovoltaic properties.The main contents and conclusions of this thesis are as follows:1)A class of“D-A”type of polymer donor materials（PBDTTS-2FQx and PBDTTS-2ClQx）based on quinoxaline derivatives（2FQx and 2ClQx）functionalized by side chains of F and Cl atoms were designed and synthesised.The effects of different halogen on the photophysical,electrochemical,thermal stability and photovoltaic properties of polymer were systematically investigated.The results show that the PBDTTS-2ClQx has wider absorption,lower HOMO energy level,lower band gap and more balanced electron migration compared with the PBDTTS-2FQx.The PSCs devices based on PBDTTS-2ClQx:Y6 obtained 14.37%of the PCE.The V_OC、J_SC and FF of the PSCs are 0.83 V,23.51 m A cm^-2 and73.63%,respectively.The results show that the introduction of Cl atoms on the side chain of quinoxaline can not only effectively boost the J_sc and FF of the device,but also avoid the influence of the larger radius of the Cl atoms on the planarity of the main chain.2)A polymer donor material（PBDTTS-2FClQx）with F and Cl atom-functionalized asymmetric side chain was designed and synthesised.The photophysical,electrochemical,thermal stability and photovoltaic properties of PBDTTS-2FClQx were systematically investigated.The results show that the asymmetric molecular structure is beneficial to increase the dipole moment and dielectric constant,reduce the exciton binding energy,enhance exciton dissociation and charge transport.The PSCs devices based on PBDTTS-2FClQx:Y6 obtained 12.90%of the PCE.The V_OC、J_SC and FF of the PSCs are 0.86 V,23.46 mA cm^-2 and 63.85%,respectively.3)A class of simple polymer donor materials（PDTQx-TT、PDTQx-2FTT and PDTQx-2ClTT）were designed and synthesized.The photophysical,electrochemical,thermal stability and photovoltaic properties of polymers were systematically investigated.The devices based on polymers:PC₇₁BM were studied.The results show that Cl atoms can effectively reduce the HOMO energy level and increase the V_oc.The PSCs devices based on PDTQx-2ClTT:PC₇₁BM obtained 3.79%of the PCE.The V_OC、J_SC and FF of the PSCs are 0.80 V,8.20 m A cm^-2 and 57.32%,respectively.The device performance of PSCs based on NFAs is under studying.