Development And Application Of New Molecular Photoelectric Characteristics Based On DPP

Dipyrrolopyrrolidone(DPP)is widely used in various optoelectronic device materials,such as organic field effect transistors(OFET),organic solar cells and other devices,etc.due to its excellent stability,large conjugate skeleton,good structural flatness and easy modification.In view of the great potential applicability of this structure,in this paper,two groups of new DPP derivatives were designed and developed,which were applied to phototransistors and molecules with mechanical force fluorescence discoloration behavior.This work further studies their possible theoretical mechanisms and expanded their practical applications.We synthesized the derivative PPAB of DPP through Schiff base formation reaction,and then polymerized PPAB with IDT and BDT monomers under the action of palladium catalyst by still coupling method to obtain two alternating copolymers P-PPAB-IDT and P-PPAB-BDT.We investigated the two polymers by fluorescence emission spectrum,absorption spectrum,DSC,XRD,AFM,cyclic voltammetry and molecular theoretical simulationand and other test methods,and found that P-PPAB-IDT has a more compact molecular stacking structure.In addition,the results show that the polymer P-PPAB-BDT is a bipolar molecule,while P-PPAB-IDT is a p-type molecule,and its hole mobility is up to 0.023 cm~2V^-1s^-1,which is nearly 20 times higher than that of polymer P-PPAB-BDT whose hole and electron mobility are about10^-3 and 10^-4 cm~2V^-1s^-1.In addition,we found that when the organic phototransistors based on P-PPAB-IDT and P-PPAB-BDT were irradiated with white light,the organic phototransistors based on polymer P-PPAB-IDT did not show any light response behavior,while the organic phototransistors based on P-PPAB-BDT showed very significant light response characteristics,and its current ratio(I_light/I_dark)under light and dark environment in p-type region was 2500,and the I_light/I_dark ratio in n-type region was 15.It is well known that the photosensitive characteristics are highly dependent on the carrier mobility of polymer semiconductors.Through the analysis of this abnormal phenomenon,we believe that the necessary condition for improving mobility:the?-?accumulation and aggregation of polymer in turn inhibit the dissociation of photogenerated carriers and accelerate the recombination of electron hole pairs,which is not conducive to the performance of photosensitivity in field effect transistors.We have discussed this phenomenon more deeply and believe that appropriately reducing the degree of polymer accumulation and molecular aggregation will help to achieve a performance balance between carrier mobility and photosensitivity.This work not only provides a new strategy for the preparation of organic field effect transistors with high photosensitivity,but also widens the way for the multi-function of OFET.In addition,in recent years,mechanofluorochromism dyes have been widely used in sensing,monitoring,biological imaging and other fields,which has attracted great attention.It is speculated that this mechanofluorochromism behavior may be mainly related to the change of the stacking structure between materials molecules under the external force.We synthesized 1,4-dimethyl-2,5-dipropyl-3,6-bis(3-cyanophenyl)pyrrole[3,4-c]pyrrole(DPP-CN-C₃)by introducing n-propyl alkyl chain into the nitrogen atom of pigment orange 71 lactam to weaken its intermolecular force and increase its solubility.Through its solid-state fluorescence spectrum,it was found that DPP-CN-C₃ showed obvious mechanofluorochromism behavior.We analyzed this phenomenon by DSC,XRD and single crystal structure analysis.It is considered that the mechanofluorochromism behavior is closely related to the change of intermolecular stacking and aggregation structure.This work not only provides a certain method and strategy for the development of new organic dyes with mechanical discoloration behavior,but also accumulates experience on how to controllably adjust the molecular structure through external action.