Effect of dye concentrations in blended-layer white organic light-emitting devices based on phosphorescent dyes

Abstract

The electronic and optoelectronic behavior of white organic light-emitting devices (OLEDs) based on blue (FIrpic) and red [Ir(piq)2(acac)] phosphorescent dyes doped into the same layer of a polyvinylcarbazole (PVK) host are reported. The conductivity of all the OLEDs studied appeared to be dominated by space-charge injection effects, exhibiting a current I versus voltage V dependence of the form I∝Vn, with n≈7 at applied voltages at which electroluminescence was observed. Systematic studies of the current versus voltage and light-emitting behavior of the OLEDs have identified different excitation processes for the two dyes. It is suggested that electroluminescence from the FIrpic molecules originates by direct transfer of the exciton energy from the PVK to the dye molecules, while the process of light emission from the Ir(piq)2(acac) molecules involves carrier trapping. The efficiency of the devices can be tuned, to some extent, by varying the thickness of the organic film. Luminous efficiencies and luminous power efficiencies of 8 cd A−1 and 3 lm W−1 were measured for these blended-layer OLEDs, with Commission Internationale de l’Eclairage coordinates of 0.35, 0.35.

Synthesis of platinum complexes of fluorenyl-substituted porphyrins used as phosphorescent dyes for solution-processed organic light-emitting devices

“…22 Initially, a layer of poly(3,4-ethylenedioxythiophene) / poly(styrenesulfonate) (PEDOT/PSS) was spin-coated onto the indium tin oxide (ITO) layer on a glass substrate, followed by a blended emissive layer. This consisted of the host, polyvinylcarbazole (PVK), together with the platinum complex (3% by weight) and 1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl) phenylene (30% by weight), denoted OXD7 (also called OXA, structure in Figure 7), as an electron transport layer.…”

Pure and Stable Top-Emitting White Organic Light-Emitting Diodes Utilizing Heterojunction Blue Emission Layers and Wide-Angle Interference

“…So it is facilitated for the holes on the red guest molecules to combine with the injected electrons from the cathode to emit red light when the red EML is located near the ETL. 29 Pure and Stable TWOLED and Its Working Principle. According to the results discussed above, we fabricate a TWOLED with the structure of glass/Ag (80 nm)/MoOx (2 nm)/m-MTDATA (25 nm)/NPB (15 nm)/TCTA:7 wt % FIrpic (15 nm)/SPPO1:7 wt % FIrpic (4 nm)/SPPO1:4 wt % Ir(MDQ) 2 (acac) (11 nm)/BPhen (10 nm)/BPhen:3 wt % Li (20 nm)/Sm (4 nm)/Ag (12 nm)/m-MTDATA (40 nm).…”

“…From Figure a, reducing the hole current by doping Ir(MDQ) 2 (acac) into SPPO1 displays that a large number of holes are trapped by Ir(MDQ) 2 (acac) molecules. So it is facilitated for the holes on the red guest molecules to combine with the injected electrons from the cathode to emit red light when the red EML is located near the ETL …”

“…So it is facilitated for the holes on the red guest molecules to combine with the injected electrons from the cathode to emit red light when the red EML is located near the ETL. 29 Pure and Stable TWOLED and Its Working Principle. According to the results discussed above, we fabricate a TWOLED with the structure of glass/Ag (80 nm Here, the thickness of HTL is slightly increased from 10 to 15 nm, and Li is doped into BPhen as the electron guest to reduce the electron injection barrier and to help the electrons to form excitons at the TCTA/SPPO1 interface.…”