Research On The Near Infrared Organic Conjugated Polymers Structures And Their Photodiode Performance

Organic photodetectors（OPD）have the advantages of processing on flexible substrates,easy large-area preparation and low cost.It has great application potential in military,industry and life.Classical organic photodetectors mostly adopt diode structure,and their devices are composed of cathode/electron transport layer/active layer/hole transport layer/anode.As the place of photoelectric signal conversion,the active layer is usually obtained by blending donor materials and receptor materials.Therefore,donor and acceptor photosensitive materials are the core factors that determine the performance of OPD,which is more prominent in the research of near-infrared OPD.In particular,the detection spectrum range exceeds 1μm is a hot spot in the research of near-infrared OPD materials in recent years.Near infrared polymer donor materials have always been the core materials of near infrared OPD research.In order to achieve spectral absorption from 400 nm to 1.5μm,it is necessary to significantly reduce the polymer band gap.The design of narrow band gap near-infrared polymer materials needs to comprehensively consider the energy level,band gap,absorption coefficient,crystallinity,phase separation behavior,solubility,film-forming,and the matching with receptor materials.In addition,the stability problem is more prominent in narrow band gap materials,which should also be carefully considered.Limited by the above problems,near-infrared polymer donor materials are difficult to give consideration to both spectrum expansion and performance improvement,and there has been no significant progress in recent years.In this thesis,the conjugated polymer materials are designed and adjusted by optimizing structural units,optimizing the main chain structure and modifying the side chain,so as to meet the needs of near-infrared OPD.The main contents and conclusions are as follows:（1）The conjugated donor polymer PQT4T-2F was designed and synthesized.PC₆₀BM was selected as the receptor to prepare organic photodetectors for testing and characterization.Polymer PTQ4T-2F has good thermal properties,LUMO energy level is-3.83 e V and HOMO energy level is-4.85 e V,The absorption spectrum range of the polymer can exceed 1400 nm,the optical band gap is less than 0.89 e V.Limited by the low solubility of the polymer,the device does not reach an excellent level.（2）Based on the problems of polymer PTQ4T-2F,a conjugated donor polymer PTQIDT was designed and synthesized.PC₆₀BM was also selected as the receptor to prepare organic photodetectors for testing and characterization.The main purpose of the design is to improve the solubility to adapt to the device process optimization and improve the LUMO energy level to achieve better exciton dissociation.The test results show that the thermal properties of polymer PTQIDT are good,the solubility is greatly improved,the LUMO energy level is-3.73 e V,the HOMO energy level is-4.93 e V,the absorption spectrum range can reach 1200 nm,and the optical band gap is 1.03 e V.The prepared OPD has great improvement in dark current suppression,hole mobility and exciton dissociation efficiency.The photoelectric performance is also better than that of PTQ4T-2F system.