Research On Non-Fullerene Organic Photodetectors Based On Near Infrared Polymers

Near infrared light has deeper penetration and lower loss in human skin tissue than visible light.Therefore,the photodetector for near-infrared light detection can better meet the application needs of wearable electronic products in the future.Compared with the traditional near-infrared photodetectors based on inorganic photosensitive materials,the near-infrared organic photodetector(NIR-OPD)has the characteristics of solution method processment,large-area preparation and flexibility,which is more compatible with the future wearable electronic technology.Therefore,it is urgent to develop NIR-OPD with high sensitivity,response and stability.At present,most of the sensitive materials in NIR-OPDs use fullerene acceptors,which show disadvantages of difficult preparation,low absorption to visible light,poor stability,easy aggregation,and so on.Therefore,the development of NIR-OPD based on non-fullerene materials has drawn a lot of attention.The key to realize near-infrared detection is to design and synthesis narrow-band-gap donors or acceptors,and then develop the NIR-OPDs based on the materials.The contents of this dissertation are as follows:Firstly,two near-infrared donor D-A polymers PTQ1 and PTQ2 were designed and prepared by using the strong electron absorption characteristics of[1,2,5]thiadiazo[3,4-g]quinoxaline(TQ)derivative unit.The characterizations show that PTQ1 and PTQ2 have a thermal decomposition temperature of more than 340?,and the optical band gap is 1.01 e V and 0.98 e V,respectively.Their absorption spectra can reach 1200nm.Based on the principle of energy level alignment,PTQ1/PTQ2 was blended with non-fullerene acceptor Y6,to prepare bulk-heterojunction active layer of diode-type NIR-OPD.All the devices can show response to 300?1300 nm light.Among them,OPD based on PTQ1 has better performance.Under 0 V bias,the largest specific detection rate(at 890 nm)is 4.0×10¹²Jones,and the specific detection rate at 1100 nm is1.25×10¹²Jones.Secondly,based on the strong electron absorption characteristics of TQ unit,a near-infrared acceptor D-A polymer PTQ3 was designed and prepared.It has a thermal decomposition temperature of more than 400?,an optical band gap of 0.98 e V,and an absorption spectrum of reaching 1200 nm.Based on the principle of energy level alignment,PTQ3 was blended with P3HT donor to prepare bulk-heterostructures active material,and then developed a diode-type NIR-OPD.The NIR-OPD has a spectral response range of 300?1300 nm,a dark current density as low as 10^-10A/cm~2under 0 V bias,and the maximum specific detection rate is 7.5×10¹¹Jones.Yet,the EQE of the device in the near-infrared region is low(less than 1%),and the device performance still has great room for improvement.However,this study opens up a new way to explore near-infrared acceptor for NIR-OPDs.