Design And Synthesis Of Organic Molecular And Their Application In High Efficiency Ternary Organic Solar Cells

Recently,organic solar cells（OSCs）are growing fast,and their performance is getting closer to that of inorganic silicon solar cells,and it has been paid much attention by researchers.Since OSCs have the advantages of low cost,flexibility and lightweight,the OSCs enjoy bright future for application.Since the ternary organic solar cells（TSCs）has a simple structure and a broad absorption spectrum,the ternary strategy has become a common way to improve the device performance of the OSCs.In order to solve the problems of narrow absorption spectrum and low mobility of the binary devices,we have synthesized a new type of small molecule DTBO.In this work,we incorporate DTBO as the third compound into the PTB7-Th:PC71BM system and PTB7-Th:IEICO-4F system,respectively,to explore the effect of the addition of the third compound on device performance.The main work of this paper is as follows:（1）Designed and synthesized a new small molecule material DTBO.In previous research,we found that adding coumarin 7 as a third compound to fullerene and non-fullerene systems can effectively improve the performance of the device,so we optimized the molecular structure of coumarin 7 to obtain a novel small molecule DTBO.As a result,the frontline orbital energy level of DTBO is much lower than that of coumarin 7,which is caused by the introduction of trifluoromethyl,and the energy level of DTBO is more matched with the host material,which is conducive to the process of charge transfer between DTBO and host material,and promotes the improvement of device performance.（2）Study the effect of DTBO on the performance of organic solar cells in the fullerene system.We doped DTBO into PTB7-Th:PC71BM system,and the power conversion efficiency（PCE）of the ternary device increased from 9.1%to 10.4%,and the short-circuit current density(J_SC)increased from 18.7 mA/cm² to 19.86 mA/cm².Fill factor（FF）increased from 62.29%to 69.02%.By comparison,the performance of the ternary device doped with DTBO is significantly better than the ternary device doped with coumarin 7,which proves that our structural optimization strategy is very effective.（3）Discuss the effect of DTBO on device performance in PTB7-Th:IEICO-4F system.In ternary devices,we realize the energy transfer from DTBO to PTB7-Th,and broaden the absorption spectrum of the devices.Finally,the PCE of ternary devices increased from 11.02%to 12.48%,and the J_SC increased from 24.94 mA/cm² to 26.43mA/cm².With the addition of DTBO,the hydrogen bond is formed between DTICO and IEICO-4F,and the existence of the hydrogen bonds has a strong impact on theπ-πstacking in the active layer,which makes the TSCs show superior charge extraction and low charge recombination.When adding DTBO to the PM6:Y6 system,a similar effect was achieved,the PCE of TSCs increased from 15.49%to 16.64%.This work provides a new strategy to introduce hydrogen bonds in ternary device and achieve higher performance.In this paper,the hydrogen bond is introduced into the ternary system to fabricate high performance ternary device.We explore the mechanism of energy transfer and the impact of hydrogen bond on the molecular stacking in the active layer,which provided a new strategy for the selection and synthesis of ternary materials in the future.