The Study Of Organic Light Emitting Device Integrated With Blue Light Emission Exciplex

This paper presents a method, which uses blue exciplex to in preparation for red,white organic light emitting devices (Organic light-emitting device, OLED). Exciplexis a common phenomenon in the study of OLED, which is generally formed at theinterface between hole transport layer (HTL) and electron transport layer (ETL).Because of the low efficiency and unstable emitting of exciplex, as well as theredshift problem, a typical approach used in the past consisted of changing thematerials or adding a blocking layer to eliminate exciplex emission. However, it hasbeen recently found that exciplex can decrease the driving voltage and improve theworking efficiency, whereas the internal quantum efficiency can reach100%. In thiswork, we take advantage of the quality of blue light emitted by exciplex and try tooptimize the WOLED structure by controlling energy transport.1.The hole transporting material TCTA and electron transporting material Bphen may form exciplex. Exciplex emission peak is incidence of red-shifted, half peak reaches70nm, and new located457nm blue emission peak is generated. Changing thecontact area between TCTA and Bphen can optimize performance of the device. Withincreasing thickness of the mixed layer, mixed structure transporting electrons and holes are more effective, reducing the light emission quenching.The increasing area between TCTA-receptors and Bphen+body, helps generate exciplex. Brightness of thedevice, the efficiency has been improved. After optimization, the maximum brightness of the device reaches1134cd/m2, and the highest lumen efficiency0.64lm/W.2. Use of TCTA and Bphen blue exciplex as the body with red phosphorescentdopant material can be prepared as a highly efficient red OLED. In this article,because of the energy of blue exciplex singlet and the triplet state is almost the same,the singlet and triplet energy matrix from exciplex blended to transfer thephosphorescent dopant is efficient. Meanwhile, TCTA， Bphen exciplexphotoluminescence spectrum and absorption spectrum of PO-01have a greateroverlapped portion, and therefore, it can be concluded that the transmitted energyfrom exciplex to PO-01is a highly efficient energy transfer process. In summary,the red phosphorescent device turn-on voltage is2.5V, the maximum brightness of it26328cd/cm2, and the maximum luminous efficiency17lm/W.3.In this study, a highly efficient fluorescent/phosphorescent white organiclight-emitting device (WOLED) was fabricated using exciplex light emission. Thehole-transport material4,4’,4’’-tris(N-carbazolyl) triphenylamine (TCTA), andelectron-transport material,4,7-diphenyl-1,10-phenanthroline (Bphen), were mixed toafford a blue-emitting exciplex. The WOLED was fabricated with a yellowphosphorescent dye, Ir(III) bis(4-phenylthieno[3,2-c] pyridinato-N,C2’)acetylacetonate (PO-01), combined with the exciplex. In this structure, the energy canbe efficiently transferred from the blend layer to the yellow phosphorescent dye, thusimproving the utilization of the triplet exciton. The maximum power efficiency of theWOLED was reached a value9.03lm/W with an external quantum efficiency of4.3%.The Commission Internationale de I’Eclairage color coordinates of the device were(0.39,0.45) to (0.27,0.31), with a voltage range of4V-9V.