New electroluminescent (EL) molecules, dissolved in a high Tg poly(aryl-ketone) (A435), have been used in double spincoated electroluminescent devices. The first EL molecule is a soluble AlQ3 derivative and the second one is a hexaphenyl-substituted isobenzofuran. The maximum solubility of both EL molecules in A435 is about 70 wt%. The typical structure of the devices is: [ITO/HTL/ETL/Mg], where HTL is a new high Tg hole transport aryl amine polymer and ETL is one of the new EL molecules in solid solution in A435. HTL is spin-coated from chloroform while the second layer is spin-coated from toluene. HTL is completely insoluble in toluene. For the devices prepared with the AlQ3 soluble derivative or for the devices prepared with the hexaphenyl-substituted isobenzofuran, the luminance has been found to increase with the EL molecule content (up to 50 ± 5 wt%) in A435. Maximum luminance values higher than 2000 cd/m2 have been measured for the soluble AlQ3 (peak emission at 545 nm) while they reach 1000 cd/m2 for the isobenzofuran derivative (peak emission at 505 nm). The luminance decreases drastically when the EL molecule content in A435 increases above 50 wt%. The current density in both double spin-coated OLEDs is quite large affecting therefore their quantum efficiency. Solutions to improve the quantum efficiency are described.
V. Jousseaume, T. Maindron, J. P. Dodelet, J. Lu, E. Shoji, A. R. Hlil, A. S. Hay, M. D'Iorio, "Double Spin-Coated Organic Electroluminescent Devices" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP16), 2000, pp 330 - 334, https://doi.org/10.2352/ISSN.2169-4451.2000.16.1.art00087_1