Recovery Act: Low Cost Integrated Substrate for OLED Lighting Development Page: 9 of 35
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Recovery Act: Low Cost Integrated Substrate for OLED Lighting Development
PPG Industries, Inc.
From Table 7, it can be seen that devices fabricated on Anode 1 resulted in lower performance as
compared to the control ITO anodes. The primary reason for this was determined to be the higher surface
roughness (R~ms-8-14nm) of these anodes resulting in current leakage and affecting the performance of
the devices. As a result of anode surface roughness, some of the devices fabricated on these anodes
showed "dead spots" which may explain the lower efficiency.
The surface roughness of these anodes was improved from 14nm to 8nm by varying the deposition
chemistry and other parameters. The laboratory-scale surface roughness improvement results were also
successfully demonstrated on a manufacturing line. Recent results on the pilot-scale CVD coater indicate
that there is the potential for even further improvement of the surface roughness of these anode layers.
Another approach that was explored is the use of a solution coated- HIL film to circumvent the surface
roughness these anodes. PPG has tested this concept in partnership with another OLED fabricator. In
preliminary studies, it has been shown that Anode 1 can be effectively planarized by using the solution
coated-HIL films. Figure 7 shows an optical micrograph of a powered 3mm x 3mm orange PHOLED
pixel that was fabricated on Anode 2 using an aqueous HIL. No "dead spots" were observed and the
device yield was much higher as compared to those fabricated without a solution coated-HIL film.
Figure 7: An optical micrograph of a powered green PHOLED pixel fabricated on Anode II showing dead spots and
an orange PHOLED pixel fabricated on Anode II using a solution coated-HIL film.
The device performance results are summarized in Table 8. It should be noted that even without
optimizing the HIL for the Anode 2, operating voltages, efficiencies and lifetimes for the devices
fabricated Anode 1 were observed to be better than those fabricated on the commercial ITO anode.
At 1000 nits
Anode Voitage (V) Current Density (mA/cm2) Luminous Efficiency (Cd/A) Power Efficiency (Lm/W) EQE (%) LT5O (hrs)
Commercial ITO 2.8 10.3 9.7 10.9 4.2 1736
Anode 1 2.79 8.9 11.3 12.7 5.2 1932
Table 8: Performance comparison of the orange PHOLED devices fabricated on Anode 1 and commercial ITO
In conclusion, this program developed and demonstrated two low-cost alternates to a conventional ITO
anode, both of which are conducive to OLED device fabrication.
Light Extraction Lavers
External Extraction Layers (EELs)
A number of scalable EEL technologies, based on the concepts of light scattering and changing the exit
angle of the light at the substrate/air interface, were evaluated under this project.. These technologies were
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Benton, Scott & Bhandari, Abhinav. Recovery Act: Low Cost Integrated Substrate for OLED Lighting Development, report, September 30, 2012; United States. (https://digital.library.unt.edu/ark:/67531/metadc831063/m1/9/: accessed May 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.