Highly Efficient Solution-processed Phosphorescent Organic Light-emitting Devices

Organic light-emitting devices?OLED?is an important research of the third generation of photoelectric display technology.Compared with the traditional technology of the information display and solid state lighting,the OLED have many advantages,such as the wide angle of view,flexible bending,large area and et al.So it has been widely focused on by the academia and the business community.Many phenomena have been found by studying the internal mechanism of OLED.Phosphorescent materials can effectively utilize both singlet and triplet excitons in order to achieve high internal quantum efficiency of the device.White OLED based on the TADF mechanism are conductive to achieving low cost and industrialization of devices.Broadening the carrier recombination region and balancing charge injection/transport can effectively improve the efficiency and stability of the device.In this thesis,a series of high-efficiency OLED is prepared using low-cost solution-process.High-efficiency phosphorescent OLED based on exciplex has been fabricated.The highly efficient and stable WOLED composed of the mixed host doped phosphorescent and TADF materials has also been discussed.1.The interfacial exciplex can be formed between the two functional layers of TPBi and NPB as the electron donor and accteptor materials.The preparation of OLED based on interfacial exciplex can effectively overcome the disadvantages of high voltage and unbalanced charge transmission.By doping the red phosphorescent dye Ir?MDQ?₂?acac?in NPB,effective energy transfer from the interface exciplex to the dye can be achieved.After optimization,the maximum current efficiency of the red OLED can reach to 30.5 cd/A,with an ultralow threshold voltage of2.6 V.The results show that the prepared red OLED is a high efficiency device based on interface exciplex.2.Interfacial exciplex can be formed with TmPyPB as the electron transport layer and the single-subject material m-MTDATA doped orange phosphorescent dye PO-01 as the luminescent layer.When mixed certain proportion bipolar material 26 DCzPPy with m-MTDATA,exciplex can be found in the co-host,whose efficient energy transfer is more efficient compared with the interfacial exciplex.Current efficiency of orange OLED after optimization can reach 30.5 cd/A,which is 1/5 higher than that of the interfacial exciplex devices.This discovery provides a new and reliable train of thought for the further study of the exciplex.3.Mixed host of TAPC and mCP have bi-polar characteristic,which are beneficial to the charge transfer balance,expanding the compound area,reducing the driving voltage and improving the device efficiency.The blue TADF material DMAC-DPS with excellent stability is good for reducing the fabrication cost.Blue devices are prepared with mixed host doping DMAC-DPS,then efficient and stable warm WOLED are optimized by doping with orange phosphorescent materials PO-01.A low turn-on voltage of 3.23 V and a current efficiency of 20.4 cd/A can be achieved with a color coordinate of?0.39,0.39?in the hybrid WOLED.