Synthesis And Photoelectric Properties Of Organic Electron Transport Materials Bearing Acenaphthenequinone Imide

Acenaphthoquinone imide（ANQNI）is regarded as a type of useful building block unit of electron transport materials due to strong electron affinity and good chemical stability.In recent years,ANQNI derivatives have been widely used to construct high-performance organic/polymer electron transport materials,which exhbits great application potential in the field of organic field-effect transistors（OFETs）and non-fullerene solar cells.In this paper,two types of ANQNI-based organic electron transport materials with A-A or A-D-A conformations are designed and synthesized.The relationship between molecular structure and photoelectric property has been studied.The detailed research contents are provided as follows:1)Benzodifurandione（-BD）and naphthodipyrrolidone（-NDP）are widely used as the building block units of electron transport materials due to their strong electron deficient properties and good backbone coplanarity.This charpter presents the synthesis and characterization of two A-A types of ANQNI-based organic electron transport materials（NAI and BAI）,in which ANQNI is used as the terminal group;-BD and-NDP are used as the parent cores.In combination with DFT calculation,the molecular structure,absorption spectrum,and energy level of the compounds are studied.The DFT-calculation results reveal that both BAI molecules show relatively good backbone coplanarity,whith the torsion angle of 6.5°,while the torsion angles of both NAI molecules is as large as 16.8°.The electrochemical test data shows that both type of NAI and BAI have very strong electronic affinities and low-lying LUMO energy levels of less than–4.0 e V,with the lowest LUMO values of up to–4.39 e V.The investigation of charge-transport properties reveals that both NAI and BAI are n-type semiconductors,with the highest electron mobilities of 4.5×10^-5 and 4.4×10^-3cm²V^-1s^-1,respectively.2)Two novel A-D-A type small molecule acceptors（A1 and A2）are designed and synthesized by adopting isatin-fused acenaphthenequinone imide or nitrogen-doped isatin-fused acenaphthoquinone imide as the terminal groups and indacenodithiophene derivative as the donor core.The effect of pyridal nitrogen on the molecular structure,optical absorption,and energy level of A1 and A2 is comparatively studied by combining density functional theory（DFT）calculation.In comparison with A1,the incorporation of pyridal nitrogen into A2 not only improves backbone coplanarity,but also achieves 27 nm red-shift in the charge transfer peak of solution absorption.Moreover,the investigation of electrochemical analysis and DFT calculation indicates that the pyridal nitrogen-containing A2 exhibits enhanced electron affinity,thereby leading to deeper-lying energy levels of the highest occupied molecular orbital（HOMO）and the lowest unoccupied molecular orbital（LUMO）as compared to its counterpart（A1）.Finally,non-fullerene solar cells containing PBDB-T:A1 or PBDB-T:A2（mass ratio 1:1）blend films are fabricated by using A1 or A2 as the electron acceptor material and commercial available PBDB-T as the donor material.The highest energy conversion efficiencies of 5.19%and 6.19% are demonstrated for A1 and A2,respectively.