Resesrch On The Preparation And Performance Of Organic Field Effect Transistor Based On Bipolar Small Molecules

In recent years,organic optoelectronic devices have developed rapidly.Among them,the organic bipolar transistor only needs a layer of bipolar semiconductor material to prepare and process a transistor to construct a logic complementary circuit CMOS inverter.However,at present,semiconductor molecules with bipolar transmission usually have a small band gap,and require high molecular energy levels,so they are relatively rare.Designing and synthesizing high-performance bipolar materials has become the current research focus of organic optoelectronic materials.The introduction of strong electron-withdrawing groups or conjugation expansion into existing unipolar materials is an effective strategy for designing and synthesizing high-performance bipolar materials.This article introduces halogen atoms or condensed thiophene into the existing air-stable unipolar materials to expand the conjugation,adjust the energy level of the molecules,and make the material change from unipolar to bipolar.My main work has the following three parts:1、Focusing on two small chlorine-containing DBP molecules(DBP-1 and DBP-1),explore the impact of chlorine substitution on molecular energy levels and carrier transport.Experimental results show that the introduction of chlorine atoms reduces the energy level and band gap of the molecule,and the maximum absorption spectrum also appears red-shifted,and the more chlorine atoms are substituted,the more obvious the phenomenon.Both DBP and DBP1 show typical P-type transmission,DBP-1 with a hole mobility of up to 0.25 cm2 V-1 s-1;while DBP-2 with a narrower band gap(Eg=1.51eV)It is bipolar,in which hole transport is 0.07 cm2 V-1 s-1 and electron transport is 0.03 cm2 V-1 s-1.2、The parent molecule DBP is fluorinated,around the fluorinated DBP-3 and DBP-4,the influence of the introduction of fluorine atoms on the molecular stacking mode and energy level is discussed.influences.The results show that the LUMO energy level of the molecules after fluorination will decrease,and the stacking method of the molecules will change,which increases the overlapping area of π-π molecules,so the charge transfer is more efficient.Both DBP3 and DBP-4 exhibit typical P-type transmission,and the hole mobility of DBP-3 is 0.40 cm2 V-1 s-1.3、Around the syn-NDTTI and anti-NDTTI,which use naphthimide as the parent molecule to condense the thiophene group,the influence of the introduction of the thiophene ring on the molecular energy level and carrier transport was studied.The results show that after the introduction of thiophene groups,the energy level of the naphthimide molecule increases slightly while the band gap decreases slightly,but the orientation of the sulfur atom has little effect on the energy level and band gap of the molecule.Both synNDTTI and anti-NDTTI exhibit bipolar transmission.The hole mobility of syn-NDTTI is 0.04 cm2 V-1 s-1,and the electron mobility is as high as 3.42 cm2 V-1 s-1.The hole mobility of anti-NDTTI is 0.04 cm2V-1 s-1,and the electron mobility is up to 5.27 cm2 V-1 s-1.