High-efficiency red electrophosphorescence devices

Adachi, Chihaya; Baldo, Marc A.; Forrest, Stephen R.; Lamansky, Sergey; Thompson, Mark E.; Kwong, Raymond C.
March 2001
Applied Physics Letters;3/12/2001, Vol. 78 Issue 11, p1622
Academic Journal
We demonstrate high-efficiency red electrophosphorescent organic light-emitting devices employing bis(2-(2[sup ′]-benzo[4,5-a]thienyl)pyridinato-N,C[sup 3[sup ′]]) iridium(acetylacetonate) [Btp[sub 2]Ir(acac)] as a red phosphor. A maximum external quantum efficiency of η[sub ext]=(7.0±0.5)% and power efficiency of η[sub p]=(4.6±0.5) lm/W are achieved at a current density of J=0.01 mA/cm[sup 2]. At a higher current density of J=100 mA/cm[sup 2], η[sub ext]=(2.5±0.3)% and η[sub p]=(0.56±0.05) lm/W are obtained. The electroluminescent spectrum has a maximum at a wavelength of λ[sub max]=616 nm with additional intensity peaks at λ[sub sub]=670 and 745 nm. The Commission Internationale de L'Eclairage coordinates of (x=0.68, y=0.32) are close to meeting video display standards. The short phosphorescence lifetime (∼4 μs) of Btp[sub 2]Ir(acac) leads to a significant improvement in η[sub ext] at high currents as compared to the previously reported red phosphor, 2,3,7,8,12,13,17,18-octaethyl-12H, 23H-prophine platinum (II) PtOEP with a lifetime of ∼50 μs. © 2001 American Institute of Physics.


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