Design,Synthesis And Device Performance Of Organic Solar Cell Acceptor Materials Based On Unfused Core

In recent years,organic solar cells have become one of the research hotspots in the field of solar cells due to their unique advantages of wide sources,rich and diverse structures,low cost,excellent mechanical flexibility,translucency and large-scale preparation and production.A-D-A(Acceptor-Donor-Acceptor)type non-fullerene acceptor materials represented by ITIC have the advantages of simple adjustment of molecular energy level and absorption spectrum,which has caused more and more researchers to pay attention to ITIC and its derivatives.Materials based on these and structural templates are also emerging.However,these A-D-A non-fullerene acceptors always have complex chemical structures,which often require complex multi-step synthesis to obtain the final products,and the preparation cost is high.This will be very detrimental to the large-scale production of materials and limit the preparation and commercial application of large-scale equipment.In order to make A-D-A type non-fullerene acceptor materials suitable for large-scale production,a series of simple and low-cost acceptor materials were designed and synthesized in this paper.The photoelectric properties of the materials were studied in detail,which provided more ideas for the design and development of organic solar cells.The main contents of this paper are as follows:(1)Two new A-D-A simple electron acceptors BTIC-H and BTIC-EH with non-fused core were developed for non-fullerene organic solar cells.Molecular BTIC-H and BTIC-EH show near-infrared absorption and uniform energy levels,but different alkyl side chains lead to differences in solubility,spectral absorption,intermolecular dihedral angle,crystallinity and photovoltaic device performance between BTIC-H and BTIC-EH.The results show that the alkyl side chains of branched chains are more helpful to the solubility of molecules than the alkyl side chains of straight chains,the dihedral angle of molecular structure is larger,and the suitable phase separation size can be formed when the alkyl side chains of branched chains are miscible with the donors.(2)The optimum conditions of solar cell devices using BTIC-H and BTIC-EH as acceptor materials were explored by selecting spin-coating solvent,adding additives and adjusting the proportion of acceptor.For BTIC-H with linear side chains,the donor was PBDB-T,and the active layer was dissolved by TCE with 1%DIO,and the performance of photovoltaic devices was the best when the acceptor was 1:1.High power conversion efficiency can reach 0.96%.For BTIC-EH with side chains,PBDB-T as donor,the ratio of PBDB-T:BTIC-EH is 1:2,and the active layer is prepared by CB spin coating with 1%DIO.The maximum power conversion efficiency is up to 2.40%.The great difference in the small molecule properties of the two receptors may be due to the better microphase separation of BTIC-EH with lower crystallinity.(3)A-D-A non-fused ring acceptor material with 3-ethylrhodanine as electron-withdrawing terminal group was designed and synthesized.It was found that the electron absorption capacity of 3-ethylrhodanine is weaker than that of 1,1-dicyanylmethylene-3-indanone,higher energy level of acceptor and less obvious decrease.Therefore,the absorption range of BTER-H with 3-ethylrhodanine as the end group is narrower,the band gap is wider,and the maximum energy conversion efficiency of the device prepared with donor P3HT can reach 1.43%.Meanwhile,thermal annealing is not conducive to the formation of good microstructures in organic solar cells' active layer with BTER-H.