Organic light emitting devices with enhanced outcoupling via microlenses fabricated by imprint lithography

We demonstrate a fluorescent/phosphorescent WOLED with a maximum external quantum efficiency of14.3± 0.3͒% at 900 cd/ m2 and power efficiency of 21.6± 0.5 lm/ W at 220 cd/ m2

Yiru Sun; Stephen R. Forrest


Scholarcy highlights

  • There has been considerable interest devoted to the optimization of white organic light emitting deviceWOLEDefficiencies at high luminescence due to their potential use as interior illumination sources
  • The microlenses are directly integrated onto the glass substrate by imprint lithography. Using these arrays in conjunction with the recently introduced fluorescent/phosphorescent WOLED structure of Sun et al.,11 we demonstrate WOLEDs with maximum external quantum and power efficiencies of14.3± 0.3͒% at 900 cd/ m2, and 21.6± 0.5 lm/ W at 220 cd/ m2, respectively
  • FIG. 6. ͑a Enhancement of power efficiency of WOLEDs using microlens arrays compared to a flat glass substrate as a function of luminance. ͑b Normalized electroluminescence spectra at a current density of J = 25 mA/ cm2 as a function of viewing angle with respect to the substrate normal
  • By interpolation of the control device power efficiency data from Fig. 5͑a, we find that the efficiency can be up to 20% higher by operating the WOLED at 33% lower current density
  • The emission spectra of WOLEDs on substrates with microlenses are largely independent of viewing angle, resulting in CRI= 87, making this simple method for increasing light outcoupling attractive for lighting and displays
  • As a result of the improvement in ␩out of 50%, the drive current density and energy consumption at a given luminance can be reduced by at least 33%, leading to potentially highly efficient lighting sources with significantly longer lifetimes
  • Microlenses placed on thin glass substrates or on the surfaces of top-emitting OLEDs can significantly improve light outcoupling while resulting in negligible degradation of high resolution display images

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