Synthesis And Properties Of Bifluorenylidene-based Organic Small Molecules For Photovoltaic Cells

Organic solar cells that convert solar energy into electrical energy have many advantages,such as being flexible,lightweight,and capable of preparing large-area panels by solution printing,and have become the research focus all over the world.At present,the synthesis process of non-fullerene acceptor materials is complicated,and the price of materials is high,which is not suitable for large-area commercial applications.Combining with the advantages and disadvantages of various active layer materials,the main purpose of the thesis is to develop new non-fullerene organic small molecular acceptors with high-efficiency and low-cost.The thesis is divided into the following three parts:?1?The new non-fullerene acceptor materials TBF-DCN-C8 and TBF-DIN-C8 were designed and synthesized by using malononitrile and 1,3-indanedion as the electron-pulling terminal groups and 9,9'-bifluorenylidene?9,9'BF?as the core.The absorption spectra of TBF-DCN-C8 and TBF-DIN-C8 are mainly from 350 nm to 500 nm,and their optical bandgaps are 2.22 eV and 2.28 eV.They belong to wide bandgap materials.The HOMO levels of TBF-DCN-C8 and TBF-DIN-C8-C8 are-5.90 eV and-5.99 eV,and the LUMO levels are-3.68 eV and-3.67 eV,respectively.The polymer P3HT was used as the donor material,TBF-DCN-C8 and TBF-DIN-C8 were used as the acceptor materials with an inverted device structure?ITO/ZnO/active layer/MoO₃/Ag?.The Photoelectric conversion efficiency?PCE?of the P3HT/TBF-DCN-C8 is 0.65%,and the PCE of the P3HT/TBF-DIN-C8 is 0.93%.?2?The non-fullerene receptor materials DTBF-IN-C8 and DTBF-IC-C8 with good symmetry and planarity were designed and synthesized,in which 1,3-indanedione and2-?3-oxo-2,3-dihydro-1H-indol-1-ylidene?malononitrile were used as electron-pulling terminal groups,with 9,9'BF as the core.The absorption spectrum of DTBF-IN-C8 is mainly from 300 nm to 550 nm,which has a significant red shift compared with the absorption spectrum of TBF-DIN-C8.Its optical bandgap is 2.18 eV.The enhancement of the symmetry of the molecule and increasement of the conjugated surface of the molecule could broaden the absorption spectrum of the material.The absorption spectrum of DTBF-IC-C8 is mainly from 400 nm to 650 nm,which has a significant red shift compared with the absorption spectrum of DTBF-IN-C8.The optical bandgap is 1.93 eV.The enhancement of the electron-pulling capability of the terminal group could effectively broaden the absorption spectrum of the material.The HOMO levels of DTBF-IN-C8 and DTBF-IC-C8 are-5.96 eV and-5.96 eV,and the LUMO levels are-3.78 eV and-4.03 eV,respectively.The polymer PBDB-T was used as the donor material,and the DTBF-IN-C8 was used as the acceptor material with an inverted device structure?ITO/ZnO/active layer/MoO₃/Ag?.After thermal annealing?TA?,the PCE was 1.10%.The polymer PTB7-Th was used as the donor material,and the DTBF-IC-C8 was the acceptor material with the inverted device structure?ITO/ZnO/active layer/MoO₃/Ag?.After solvent annealing?SVA?,the PCE is 4.35%.?3?The narrower band gap non-fullerene acceptor materials TTBF-IC-C8 and DTBF-IC-C8 were designed and synthesized by using 2-?3-oxo-2,3-dihydro-1H-inden-1-ylidene?malononitrile and2-?5,6-dichloro-3-oxo-2,3-dihydro-1H-inden-1-ylidene? malononitrile as electron-pulling terminal groups and 9,9'BF as the core.The absorption spectrum of TTBF-IC-C8 is mainly from 400 nm to 750 nm,which has a significant red shift compared with the absorption spectrum of DTBF-IC-C8.Its optical bandgap is 1.69 eV.The position of the substituent has an effect on the absorption spectrum of the material.The absorption spectrum of DTBF-IC-C6 is mainly from 400 nm to 700 nm,which has a significant red shift compared with the absorption spectrum of DTBF-IC-C8.Its optical bandgap is 1.82 eV.Introducing a chlorine atom into a terminal group can enhance the electron-pullinging ability of the terminal group,and broaden the absorption range of the material.The HOMO levels of TTBF-IN-C8and DTBF-IC-C6 are-5.81 eV and-5.94 eV,and the LUMO levels are-4.12 eV and-4.12 eV,respectively.The polymer PTB7-Th was used as the donor material,and the TTBF-IC-C8was used as the acceptor material with an inverted device structure?ITO/ZnO/active layer/MoO₃/Ag?.After SVA,the PCE was 3.52%.