Synthesis And Properties Of Thiophene-based Non-fullerene Small Molecule Acceptor Materials In Yinda Province

With the rapid development of society,energy shortage and environmental pollution have become increasingly serious.Seeking green and renewable energy is the best solution.Solar energy is widely concerned because it is an inexhaustible resource.Organic solar cells(OSC)become the research hotspot and frontier in photovoltaic field because of various advantages,such as low cost,light weight,being environment-friendly,flexible processing,solution processing,simple manufacturing process and good power conversion efficiency(PCE).Fullerene acceptor materials used to play a leading role.However,the performance of fullerene-based OSCs is severely limited by the intrinsic shortcomings of fullerene acceptors,such as difficult separation and purification,limited energy level tunability,high production cost,weak visible light absorption and poor morphology stability.Recently,nonfullerene acceptor materials have attracted more and more attentions because of their advantages of simple synthesis,low production cost and adjustable energy levels.Due to the excellent crystallization and large conjugation properties of fused ring acceptor materials,they are popular in nonfullerene acceptor materials.Therefore,in this thesis,we mainly focus on the three fused rings of indacenodithiophene 38(IDT38),indacenodithienothiophene 33(IDTT33)and indacenodithienothiophene 45(IDTT45)as donor units.Terminal groups with different electron withdrawing abilities are introduced by Knoevenagel condensation.Three series nonfullerene organic small molecule acceptors were designed and synthesized.The thermal,optical and electrochemical properties of the twelve compounds were characterized and analyzed.Based on the above performance,the suitable donor polymer was selected to prepare OSC devices.The photovoltaic performance of the OSCs was tested,and the morphology of the blend films was observed.The first chapter briefly introduces the development process,device configuration,working principle and important parameters of OSCs.Then we focus on the nonfullerene small molecule acceptor materials.Finally,the design ideas and research contents of this paper are briefly described.In chapter 2,by Knoevenagel condensation,six organic small molecule acceptor compounds were synthesized by using IDT38 as the donor unit.First,the thermal properties of these six compounds were characterized and analyzed.The thermal decomposition temperatures(Td)of IDT38-ICTh,IDT38-IC2F,IDT38-IC2Cl and IDT38DMIO are above 300?,indicating their good thermal stability.However,IDT38-FOD and IDT38-ClOD have slightly worse thermal properties.The maximum absorption wavelength of IDT38-ICTh,IDT38-IC2F,IDT38-IC2Cl and IDT38-DMIO is about 700 nm,which benefits for absorbing sunlight.However,the maximum absorption wavelength of IDT38-FOD and IDT38-ClOD is about 600 nm.These six compounds have deep LUMO energy levels,which facilitates the charge transport.The LUMO level of IDT38-IC2C1 is-4.08 eV,which is the deepest one of the six compounds.The OSC devices were fabricated using IDT38-ICTh,IDT38-IC2F,IDT38-IC2Cl and IDT38DMIO as acceptor materials and PM6 as donor material,showing good photovoltaic performance.The PCE values are 8.66%,6.51%,9.79%and 8.92%respectively.Among them,the device with IDT38-IC2Cl as the acceptor material has the best performance.The EQE of these four devices is above 70%in the wavelength region of 550 to 700 nm.Both IDT38-FOD and IDT38-ClOD have poor absorption and stability.So,the photovoltaic performance of OSCs is expected to be poor.Therefore,we chose to dope IDT38-FOD and IDT38-ClOD into(FA)0.85(MA)0.15PbI3 perovskite solar cells.It can be seen from atomic force microscopy(AFM)and scanning electron microscopy(SEM)that the doping can realize smooth and regular surface of the blend film and optimize surface passivation.The photovoltaic performance was improved at the doping concentrations of 2%and 10%.The PCE of the device with 10%concentration reached 21.89%,which was 2.33%higher than that of the device without IDT38-C10D.In chapter 3,using the same Knoevenagel condensation as in chapter 2,three organic small molecule acceptor compounds,IDTT33-ICTh,IDTT33-IC2F and IDTT33-IC2C1 were synthesized by using IDTT33 as the donor unit.The Td values of these three materials were about 300?,showing good thermal stability.The three compounds have high glass transition temperatures,indicating excellent morphological stability.In addition,these three compounds showed proper absorption spectra and energy levels.The maximum absorption wavelength of IDTT33-IC2Cl is nearly 800 nm in the film state.The LUMO energy levels of the three compounds are about-4.00 eV.Using these three compounds as acceptor materials,PBDB-T is adopted as donor material to prepare OSCs.The photovoltaic performance of PBDB-T:IDTT33-IC2F device is best of the three with a PCE of 6.12%.In chapter 4,using Knoevenagel condensation,three organic small molecule acceptor compounds,IDTT45-ICTh,IDTT45-IC2F and IDTT45-IC2C1 were synthesized by using IDTT45 as the donor unit.The three compounds have high Td above 300?.The maximum absorption wavelength of the compounds is around 750 nm.The LUMO levels of the three compounds are quite deep at-4.00 eV.Using these three compounds as acceptor materials,PBDB-T is adopted as donor material to prepare OSCs.The PCE values of the devices based on IDTT45-ICTh,IDTT45-IC2F and IDTT45-IC2Cl are 4.00%,5.02%and 6.38%,respectively.The photovoltaic performance of PBDB-T:IDTT45-IC2C1 device is best of the three with a VOC of 0.776 V,a Jsc of 14.51 mA/cm2 and a FF of 56.64%.The photovoltaic performance can be improved by optimizing the device configuration.Finally,the fifth chapter summarizes all the research contents in this thesis,and analyzes the prospect of solar cells in the future.