Polymer light-emitting diodes luminance efficiency

V. Blyznyuk, B. Ruhstaller, P.J. Brock, U. Scherf, and S.A. Carter, Self-assembled nanocomposite polymer light-emitting diodes with improved efficiency and luminance, Adv. Mater., 11 1257-1261, 1999. 

Subsequently, Cao et al. [30,31] designed and synthesized polymer 20-22 by similar method and the highly efficient saturated red-phosphorescent polymer light-emitting diodes (PLEDs) were achieved on the basis of copolymer 20. The best device performances are observed with an external quantum efficiency of 6.5% photon/electron (ph/el) at the current density of 38 mA/cm2, with the emission peak at 630 nm (x = 0.65, y = 0.31) and the luminance of 926 cd/m2. 

Another way to introduce Ir(III) complexes into the main-chain of polyfluorenes was realized by Suzuki polycondensation of fluorene segments and /3-diketone ligand chelated with Ir(III) chloride-bridged dimmer (polymer 26 and 27) [34,35]. A saturated red-emitting polymer light-emitting diode was achieved from the device ITO/PEDOT/polymer 27 + PBD (40%)/Ba/Al with the maximum external quantum efficiency of 0.6% at the current density (J) of 38.5 mA/cm2 and the maximum luminance of 541 cd/m2 at 15.8 V. 

Due to the large band gap and high triplet energy level of the poly(3, 6-dibenzosilole) 5, the copolymer is an excellent host for the fabrication of blue polymer phosphorescent light-emitting diodes. A high external quantum efficiency (t/el) of 4.8% and a luminance efficiency of 7.2 cd/A at 644 cd/m2 have been achieved for blue phosphorescence devices (emission peak (AEL) at 462 nm, CIE coordinates x = 0.15,y = 0.26). The performances of the devices are much better than those reported for blue phosphorescent devices with poly(A--viny 1 cabarzo 1 e) (PVK) as the host.32... 

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