Design,Synthesis And Device Characterization Of Wide Band Gap Polymer Donor Photovoltaic Materials

The research and utilization of solar energy are effective ways to solve the energy crisis and environmental pollution caused by traditional energy sources.Many types of solar cells have been developed since their creation.Among them,characteristics of organic solar cells(OSCs)are lighter weight,lower cost,and environmental friendliness.Therefore OSCs have become the focus of research in many types of solar cells.The main measure of organic solar cells is power conversion efficiency,and the key factor affecting power conversion efficiency is the active layer material.The wide band gap polymer donor can be matched with the narrow band gap acceptor,and the wide energy level is conducive to improving short circuit current and open circuit voltage.Based on this,the design and synthesis of wide band gap polymer donor and the structure-activity relationship between molecular design and device performance are explored.The research in this paper is based on BDT-T,an electron donor unit commonly used in wide band gap polymer donors.Firstly,on the basis of the currently promising wide band gap polymer donor PBDB-T-2F,a wide band gap polymer donor PBBDDE whose ester group is modified to the electronic unit BDT-T is designed.By introducing an electron-withdrawing group ester group,the highest occupied molecular orbital(HOMO)energy level was reduced from-5.47 e V of PBDB-T-2F to-5.55 e V of PBBDDE,so that the open circuit voltage of the device constructed by PBBDDE and Y6 was increased to0.87V。Finally,the construction of the polymer donor material with low HOMO energy level was realized.Secondly,two kinds of electron donating group,fluorine atoms and ester groups,modified thiophene ethylene thiophene wide-band gap polymer donors PBTVT-1 and PBTVT-2 were designed.The TVT unit used can maintain a good plane and conjugate,and the introduction of electron-withdrawing groups keeps the HOMO level of the material at a low level.According to previous reports,the introduced fluorine atoms will form hydrogen bonds with the double bond,which will enhance the planarity of the molecule,resulting in serious morphological aggregation,in the active layer,thus limiting the performance of the device based on PBTVT-1;However,due to its large steric hindrance,the flexible ester group can improve the solubility of the material,so it is more effective in adjusting the morphology.By building a binary system with the non-fullerene acceptor material IT-4F,the PBTVT-2: IT-4F system constructed in this paper finally achieves an efficiency of 11.0%,which is the best performance of the polymer donor based on TVT unit.By modifying the electron donating unit and the electron withdrawing unit of the wide band gap polymer donor material,the influence of the introduced electron withdrawing group on the overall performance of the material is explored.A potential electron-withdrawing unit is designed,and this paper provides an effective reference for the later research of organic solar cells.