Synthesis And Device Characterization Of Polymer Donor Materials Based On Simple Non-fused Structure

As a new type of clean energy technology,organic solar cell(OSC)has become a research hotspot in recent years due to its advantages of low cost,lightweight,and capability to fabricate large-area devices.At present,the conventional structure of OSC is the bulk-heterojunction,and the active layer based on the structure is mainly mixed by donor and acceptor materials.The donor materials are mostly p-type polymers or small molecules,while acceptor materials can be classified into three categories:fullerene derivatives,n-type fused ring small molecules and polymers.At present,most of the high-efficiency polymer donor materials are based on benzodithiophene(BDT)unit with fused ring structure.However,the unit is relatively complicated,non-easy synthesis and high-cost,which is not conducive to industrialization,so polymer donor materials constructed by non-fused units with low-cost and easy synthesis,have attracted extensive attention in this field.Recently,OSCs constructed by polymer PTQ10 with non-fused structure have obtained an efficiency of 17.7%,which proves that polymer donor materials constructed by non-fused units have great potential in meeting the commercialization requirements of low-cost and high-efficiency.However,most solar cells based on polymer donor materials with non-fused structure still have lower performance.The main limiting factors is that the type of materials is scarce polymers,and most materials have shallow highest occupied molecular orbital(HOMO)energy levels,which are not conducive to obtaining high open circuit voltage(Voc).Therefore,the development of novel non-fused polymer donor materials with low HOMO energy level is one of the research hotspots.In the paper,a non-fused polymer donor material PDTCT based on thiophene unit,was designed and synthesized,and the polymer is designed on the basis of the current potential polythiophene derivative PDCBT.By introducing an electron-withdrawing carbonyl group on the thiophene to replace the ester group of the PDCBT material.The interaction between the oxygen atom on the carbonyl group and the sulfur atom on the thiophene ? bridge is still satisfied,and simultaneously achieves the purpose of reducing the HOMO energy level of the polymer.And using Friedel-Crafts acylation reaction to introduce the thiophene alkyl chain on the side chain carbonyl,a new simple non-fused ring polymer donor material was obtained.It was found that the HOMO energy level of the polymer successfully dropped from-5.26 eV of PDCBT to-5.31 eV,which achieves the design target,and the best device efficiency based on PDTCT/Y6 was 5.64%.In the paper,a series of simple non-fused polymer donor materials based on benzene units,PTDCT-2T,PTDCT-2FT,and PTDCT-2T-2FBTA,also were designed and synthesized.These polymer materials are designed on the basis of PPDT2FBT,a polymer with relatively low HOMO energy level among non-fused polymer donor materials.The same design concept is used to introduce carbonyl and thiophene alkyl chains on the benzene ring,thereby obtaining a novel electron donating unit.By adjusting different electron withdrawing units,a series of polymer donor materials with low HOMO energy levels were successfully synthesized.Among them,the HOMO energy level of PBCT-2T is-5.65 eV,the HOMO energy level of PBCT-2FT is-5.77 eV,and the HOMO energy level of PBCT-2T-2FBT is-5.80 eV,realizing the construction of polymer donor materials with low HOMO energy level.