The Design,Synthesis And Photovoltaic Properties Of Non-fullerene Acceptor Molecules Based On IDT Central Cores

In the recent years,organic solar cells(OSCs)have been popular among scientists due to their advantages,such as flexibility,light weight,low cost,solution-processed and large-area fabrication.Excellent active blend plays an important role in the improvement of cell performance,yet the rapid development of nonfullerene acceptor(NFA)molecules---which are the emerging acceptor materials of active blend---largely pushes the process of OSCs.The NFA-based OSCs have achieved the power conversion efficiency of 18%in single-junction devices now.The distinctive potentials make them to be the main acceptor materials,for example,strong absorption among visible-near infrared region,the adjustment of energy levels,simple synthesis and stable properties.This thesis designs and synthesizes three A-D-A type nonfullerene acceptor molecules,they are IDT-C₆-4F,IDT-C₁₆-4F and IDT-C₁₆-4Cl,respectively,and studies their corresponding photovoltaic performance.1.The non-fullerene acceptor of IDT-C₆-4F is synthesized by using n-hexyl modifying indacenodithiophene(IDT)as the donor unit and end-capped by difluorodicyanoindandione(IC-2F)acceptor units.This molecule has suitable LUMO and HOMO energy levels and matched with PM6,strong absorption among near infrared region.When blending with PM6 at the weight ratio of 1:1,the binary cell gained the PCE of 10.83%.The complementary absorption of acceptor and donor helps to obtain the J_SC of 19.18 m A/cm²,the effective film morphology facilitates charge transport,thus getting the FF value up to 71.21%and V_OC up to0.7892 V.2.The non-fullerene acceptors of IDT-C₁₆-4F and IDT-C₁₆-4Cl are designed and synthesized by taking n-hexadecyl alkyl modifying indacenodithiophene(IDT)as donor units,and end-capped by IC-2F and dichlorodicyanoindandione(IC-2Cl)acceptor units,respectively.It has found that both of two molecules have fine thermal stability,suitable energy levels and strong absorption.Moreover,when blending with PM6 at the weight ratio of 1:1.4,the binary cells achieve 9.61%and 9.55%PCE respectively,which may originate from the matched energy levels and complementary absorption between donor and acceptor molecules,AFM and TEM images both show that IDT-C₁₆-4F-based blend has uniform and smooth surface,smaller fibral network,thus benefiting to charge separation and transportation in the cell device and obtaining a higher photovoltaic performance.