Design,Synthesis And Photovoltaic Applications Of Non-Fullerene Small Molecular Acceptors

As a new generation of photovoltaic technology,organic solar cells（OSCs）were widely studied by researchers.In organic solar cells,the most important part is the photoactive layer,which is composed of an electron donor material and an electron acceptor material.Compared with the abundance of donor materials,excellent acceptor materials are scarce.In this study,a series of electron acceptors were designed and synthesized.Their basic properties and photovoltaic applications were studied.（1）Utilizing the non-covalent intramolecular interactions and hydrogen bond interaction of O--S,S--F,F--H and O--H,three novel completely non-fused ring small molecular acceptors（2FTT-4F,2FTT-4Cl and 2FBT-4F）were designed and synthesized through Stille coupling reaction,Knoevenagel condensation reaction,alkyl nucleophilic substitution reaction,and Vilsmeier-Haack reaction.Only five steps were required to synthesize each material,with total yields of 18%,17%and 14%for 2FTT-4F,2FTT-4Cl and 2FBT-4F.Optical,electrochemical,molecular configuration,and photovoltaic properties of the three materials were studied.The results show that the three molecules have strong absorption between 500 and 800 nm.The devices based on PM6 and the three acceptors achieved a maximum PCE of 3%,along with a highest Voc of 1.048 V.（2）A series of large conjugated dimer small-molecule acceptors（D-DTPBT-4F,D-DTPBT-4Cl,D-DTPBT-2OH,S-DTPBT-4F and S-DTPBT-2OH）were constructed by linking DTPBT units with linkage units（single and double bonds）using the molecular design strategy of non-fused ring.Stille coupling reaction,Cadogan reduction cyclization,Knoevenagel condensation reaction,alkyl nucleophilic substitution reaction,and Vilsmeier-Haack reaction were used to synthesize the five materials.Only eight steps were required to synthesize each material,with total yields of 15%,19%,14%,14%and 18%for D-DTPBT-4F,D-DTPBT-4Cl,D-DTPBT-2OH,S-DTPBT-4F and S-DTPBT-2OH.The corresponding optical,electrochemical,molecular configuration,and photovoltaic properties were investigated.The results show that the dimer molecules have strong near-infrared absorption（absorption edge is around 1000 nm）and strong intermolecularπ-πstacking.The neat film electron mobilities of the five dimer acceptors were measured by SCLC method with the highest mobility of 4.15×10^-4cm² V^-1 S^-1,indicating that these materials have good electron transport ability.