Preparation And Photoelectric Property Investigation Of The Organic Donor-acceptor Complexes

Organic donor-acceptor complex is a new emerging organic semiconductor class,and its preparation procedure is simple and green,without additional complicate synthesis processes,through liquid,gas or solid phase mixing,relying solely on intermolecular interactions（charge transfer,π-πinteraction,hydrogen bond,halogen bond,etc.）to form highly-ordered molecular-level heterojunction（donor-acceptor cocrystal）.However,due to the limited numbers of component to construct high-performance donor-acceptor complexes,the supramolecular framework is difficult to precisely predict,and greatly affected by the preparation environment and the nature of the material.There are still many difficulties and challenges in the investigation of high-performance and multifunctional organic donor-acceptor complexes.Based on the above considerations,this thesis takes organic donor-acceptor complexes as the main research object,and anovel multifunctional donor-acceptor complexes are prepared by selecting appropriate donor and acceptor materials.The study was carried out through the analysis of crystal structure,the characterization of physicochemical properties and optoelectronic properties,and furthers the structure-property relationship.The main contents are as follows:（1）With the fast development of organic electronics,organic semiconductors have been extensively studied for various optoelectronic applications,among which organic phototransistors recently emerged as one of the most promising light signal detectors.However,it is still a big challenge to endow organic phototransistors with both high mobility and high light-sensitivity because the low mobility of most organic photoresponsive materials limits the efficiency of transporting and collecting charge carriers.Herein,we developed photodetectors based on new organic donor-acceptor complex with high mobility and long wavelength range photoresponse.The hole mobility of DFD/TMTES-P nanowire device is as high as 1.12 cm² V^-1 s^-1,and high photosensitivity in the long wavelength range of 300-1000 nm was found.It exhibits responsivity of5.3×10³ A/W and detectivity of 0.51×10¹⁴ Jones under 365 nm wavelength-light illumination and responsivity of 3.9×10⁴ A/W and detectivity of 1.0×10¹⁴ Jones at 800 nm wavelength-light illumination.In contrast,the DFD/TIPS-P nanowire device exhibited a hole mobility of 0.27 cm²V^-1 s^-1,but poor stability.This research heralds the potential of charge-transfer complexes for photodetection applications in a wide spectral range,even in the near and mid-infrared regions.（2）Developing novel high-performance n-type semiconductors is of great importance for the organic electronics.Perylene/TCAF donor-acceptor complex polymorphs were grown by adjusting cocrystal nucleation conditions.Theα-cocrystal obtained during the natural cooling process was a thermodynamically stable phase,and when an extra force（shaking）is introduced,the reduction of the nucleation energy barrier promotes the formation of a metastableβ-cocrystal.Among them,the mixed stacking columns ofα-cocrystal are composed of Ziagzag-type stacking column with a slip angle of 61°and Linear-type typical mixed stacking column.Theβ-cocrystal complex own herringbone packing pattern,and the goodπ-πoverlap between alternate TCAF/perylene pairs was supposed to establish an efficient electron transport route.The electron mobility of theα-cocrystal single-crystal transistor device is 0.06 cm² V^-1 s^-1,while the performance of theβ-cocrystal generated by heterogeneous nucleation reaches to 0.88 cm² V^-1 s^-1.This polymorphs-regulated cocrystal engineering strategy provides us a new way for the development of high-performance n-type organic semiconductors and also helps to explore the relationship between structure and performance.（3）Organic photochromic materials have drawn considerable attention for their potential applications in large-scale and low-cost optoelectronics owing to unique tunable physicochemical properties.Here,luminescent acene-based small molecules（Perylene and Pyrene）and DCAF were selected as electron donor and electron acceptor,respectively,to synthesize two organic-complexes of DCAF/Perylene and DCAF/Pyrene.The differed donor molecules lead to the differences in resuled aggregating structure,morphology and luminescence properties:the DCAF/Perylene complex possess typical H-type aggregation mode,with no obvious luminescence,and as-prepared nanowires are twisted.However,the stacking degree of the donor and acceptor molecules in the DCAF/Pyrene complex stacking mode is greatly weakened,resulting in a weaker ACQ effect,which presents red luminescence and one-dimensional linear packing architecture.Through molecular design of organic fluorescent or helicoidally materials is an efficient strategy to deeply understand their structure-activity relationships,which pave a potential path to develop novel functional supramolecular systems.