Research Of Near-infrared Organic Photodetector Diodes Based On Non-fullerene Acceptors

The development of near-infrared organic photodetectors has been driven using near-infrared light and electricity in human applications.Organic photodetector based on binary materials have attracted attention due to their simple preparation process,high performance,and low cost.The photoactive layer materials mainly consist of bulk heterojunction composed of fullerene and its derivatives,which have limitations such as difficult chemical modification and instability due to photodimerization.To overcome these limitations,non-fullerene acceptors have emerged as an adjustable alternative.In this thesis,two types of non-fullerene acceptor small molecules were synthesized,the BTIC series and the TTD（DTC-2FIC）₂,and near-infrared organic photodetectors based on these molecules were prepared.Comprehensive characterization tests provided a full understanding of these molecules at the material and device physics level.The BTIC series was synthesized with different number of Fluorine atoms,and their lowest unoccupied molecular orbital gradually deepened from-3.93 e V to-4.22 e V,matching most polymer donors.Mixing d FBTIC4F with TQ_me（DTC-IC）₂ resulted in an all-small-molecule near-infrared organic photodetector.Fluorine atoms changed the absorption range,molecular planarity,and film-forming properties.The relatively poor device performance was due to material crystallinity and film-forming properties.A narrow-bandgap near-infrared non-fullerene acceptor small molecule,TTD（DTC-2FIC）₂,was also synthesized with a bandgap as narrow as 1.10 e V,achieving broad-spectrum absorption from 300 nm to 1300 nm.Mixed with PCE10,it achieved performance with external quantum efficiency of over 10%and specific detectivity exceeding 10¹¹ Jones.The relatively high performance was owing to uniform phase separation,low roughness,and goodπ-πstacking,making charge transfer more efficient.However,comparatively strong bimolecular recombination and Shockley-Read-Hall recombination hindered further optimization.Overall,this thesis presents the synthesis of new non-fullerene acceptor small molecules,providing new ideas for near-infrared organic photodetector research.