The Influence Of Fluorescent Exciplex On The White Organic Light-Emitting Device

Organic Light-Emitting Device(OLED) has already attracted a great deal of attention in the last decades because of their promising applications such as high luminance, low driving voltage, flexible substrate and so on. Especially, white OLED(WOLED) has gained growing interests owing to their broad utilization in backlighting for liquid crystal displays, solid-state lighting and full-color displays with color filters. In order to produce the efficient WOLED, various methods have been employed. The most widely used approach is to utilize the multiple emission materials to realize ideal white light, thus using multiple emission layers. This way would complicate the processes of device fabrication. Alternatively, the WOLED based on exciplex can solve this problem well. In this work the characteristics of two novel 1,8-Naphthalimides derivatives materials and devices based on them have been scrutinized. Also, the WOLED based on exciplex emission with FluONI was fabricated. Furthermore, the exciplex emission has been systematically investigated. The detailed content is as following:(1)After the characteristics of two novel 1,8-Naphthalimides derivatives, FluONI and BimPh ONI, were investigated, the OLEDs were fabricated using them as electron transport materials(ETMs) and emission layer. We proved the emission peak located around 460 nm came from FluONI and BimPhONI exciton emission, and the new peak about 580 nm was from exciplex at the organic heterojunction between NPB and FluONI or BimPhONI instead of electroplex.(2)Based on FluONI, the commonly used hole transport materials(HTMs) were chosen in our study as the donors, such as m-MTDATA,TAPC and NPB, to adjust the color in the devices. The device using m-MTDATA as a donor only had an emission peak at 680 nm, which came from exciplex, and its luminance and efficiency was low; the emission of the device using TAPC resulted from the FluONI exciton emission and exciplex emission; when choosing NPB as the HTM, and the CIE coordinates got into(0.37, 0.37) at a driving voltage of 5 V, which was close to the ideal white light, and the luminance and efficiency of this device were relatively high.(3)To further tailor the color, choosing NPB as the HTM, we adjusted the thickness of FluONI in device. When the thickness of FluONI was 30 nm, the device yielded an ideal white light, the CIE coordinates moved into(0.33, 0.33). Then we studied the mechanism of exciplex emission between the heterojuction of NPB/FluONI, and verified that the new red-shifted emission was from exciplex via empirical formula of energy radiation. At last we analyzed the electronic characteristic of the white device.