Synthesis And Performances Of Organic Photoelectric Materials Based On DTBDT And Twin Spiro-type Core

Under the background of the shortage of energy and a deteriorating ecological environment,polymer solar cell?PSC?,as a significant part of organic electronics,has been more and more popular in the field of the new energy.Although there is some limitations related to lower efficiency compared with the pervoskite and silicon solar cells,polymer solar cell have pushed the development of photovoltaic technology because of the low cost,light-weight,flexible and semi-transparency properties.On the basic of the study,we focused on the active layer of PSCs and synthesized two polymer donor materials based on the DTBDT and two small molecules based on the DTF core.The structures of intermediates and final products were confirmed using nuclear magnetic resonance and mass spectra.The main research contents are shown as follow:1.The dithiazide[2,3-d:2',3'-d']benzo[1,2-b:4,5-b']dithiophene?DTBDT?,BDT fused ring extension derivative,has been developed to a star core of polymer as it has a larger conjugated surface than BDT and similar power supply capability as BDT.We synthesized two polymers named PDBT-2F and PDBT-2Cl by the DTBDT as donor group and BDD as acceptor group of polymer.PDBT-2F/PDBT-2Cl was introduced by two F/Cl atoms to the side thiophene.We study the effects of two type of halogen atom on the optical physics,electrochemical,and photovoltaic performance,respectively.The device based on PDBT-2F:IDIC blend achieved a PCE of 12.01%on account of strong electronegativity of fluorine atoms,which enhanced the charge extraction and transfer between molecules by the interaction force of F-S/F-H.The device based on PDBT-2F:IT-4F blend achieved a PCE of 10.3%.On the contrary,the device based on PDBT-2Cl:IDIC and PDBt-2Cl:IT-4F blend performed a low PCE of 7.58%and 6.54%,respectively.The atom radius of chlorine is so large that the planar property of the whole molecule becomes worse and the heavy atom effect of the side group makes the molecular accumulation and the efficiency of the device worse.2.In this work,we have developed two A1-A2-D-A2-A1 type small molecule electron acceptors?DTFBT-1,DTFBT-2?with twin spiro-type core structure as D unit,3-ethyl-rhodanine?R?or 2-?1,1-dicyanomethylene?rhodanine?RCN?as A1 unit.benzothiadiazole?BT?as A2 unit.The organic solar cells?OSCs?based on the acceptors DTFBT-1 or DTFBT-2 blended with donor J71 achieved the power conversion efficiency?PCE?of 3.35%and 4.40%,respectively.The twin spiro-type core structure with a good planarity facilitates the stacking of molecules.Especially,DTFBT-1 and DTFBT-2 based devices exhibited a high V_occ of 1.15 V and 0.96 V for as-cast film due to the high LUMO of acceptors.DTFBT-2 based device showed a bigger short circuit current density(J_sc)?8.35 mA/cm²?due to the RCN of excellent electron-accepting ability.