The Study On Near-Infrared Organic Photodetectors Based On BODIPY Dyes

Photodetectors have important applications in many fields,such as optical communications,day and night surveillance,full color imaging,machine vision,and medical electronics.Although the currently dominant inorganic semiconductor-based photodetectors show excellent performance,they have some shortcomings,such as complicated process,high cost,and lack of flexibility.What’s more,in systems that require narrowband detectors,filters are necessary,which complicates the design of the image sensor.Organic photodetectors（OPD）,however,have attracted wide attention because of their adjustable response spectrum range,flexibility and low-cost manufacturing process.Unfortunately,most organic photodetectors only response to visible light,and near-infrared（NIR）photodetectors need to be further developed.Although some photoconducting（photomultiplier）organic photodetectors that respond to near-infrared light have high responsivity and external quantum efficiency,the long response time limits their applications only in some cases that do not require high response speed.In the case of dynamic or high-speed response fields,photoconductors cannot meet the requirements of applications.Therefore,both broadband and narrowband near-infrared photodetectors require further research to provide better detection capabilities and shorter response times to meet the requirements of scientific research and real applications.To solve the problems in broadband and narrowband near-infrared organic photodetectors,we proposed the corresponding solutions respectively.The contents of this thesis mainly include the following two parts:1.UV-vis-near infrared broadband organic photodetectors based on BODIPY dyesWe studied a broadband organic photodetector based on BODIPY derivative（named BODIPY-F）as donor and PC₆₁BM as acceptor,and its response covers UV-Vis-NIR（300-900 nm）spectral region.In the bulk heterojunction blends,the weight ratio of donor（BODIPY-F）and acceptor(PC₆₁BM)was adjusted to optimize device performance,and the best responsivity of 40 mA/W（at840 nm）under-1 V bias was obtained when BODIPY-F:PC₆₁BM is 0.2:1 in weight ratio.The response time was as short as 4μs and the cutoff frequency was up to 90 KHz.In addition,the detectivity exceeded¹0¹¹ cm?Hz^1/2?W^-1.It could response effectively to optical signals with a frequency below 90 KHz without obvious degeneration.By evaporating a 10 nm C₆₀ between the active layer and the cathode,the response time of the device was 500 ns corresponding to the cutoff frequency of 700 KHz,which significantly optimized the frequency response characteristics of the photodetector.Finally,the device was applied to the optical communication circuit,in which the detector receives the laser signal modulated by the audio signal,and completes the experiments of near-infrared and visible light communication,which demonstrates the practicability of the device.2.Narrowband near-infrared organic photodetectors based on BODIPY dyesIn order to realize a narrow-band responsive organic photodetector that has a specific response to NIR light,we used a series of BODIPY derivatives with narrowband spectral absorption in the NIR region as additional components and incorporated them into the bulk heterojunction blends,in which P3HT as dominating donor and PC₆₁BM as acceptor.This strategy was very beneficial to the implementation of high performance OPDs.The devices with high responsivity to NIR light were screened out and then the P3HT:PC₆₁BM mixture film was spin-coated on the transparent substrate as filters to prepare a narrowband OPDs responsive to NIR light near 750 nm,and the full-width-at-half-maximum（FWHM）was about 86 nm.The external quantum efficiency（EQE）was more than10%,and a specific detectivity of more than 10¹¹ cm?Hz^1/?W^-1 at a bias of-1 V was obtained.The device exhibited narrowband response and anti-interference ability.