CDT reports new records for OLED display materials

Cambridge Display Technology has reported red- and blue-emitting OLED materials with long lifetime and high efficiency.

Cambridge Display Technology (CDT) has announced two major milestones in the development of long lifetime, high efficiency light emitting polymers for full color, video capable displays.

A phosphorescent red device has been produced by CDT and Sumitomo Chemical which has a lifetime [see footnote] of half a million hours from an initial luminance of 100 cd/m2; this is a record for lifetime of solution-processable materials of any color.

The efficiency is also improved at over 7cd/A. Red efficiency is especially important as this color consumes the largest share of power input in a color device, so improvements in red efficiency have important practical implications.

The second major milestone announced is a lifetime of 150,000 hours for a fluorescent blue device based on a new material developed by CDT, and now part of the Sumation™ portfolio. Just eighteen months ago, CDT announced the achievement of 30,000 hours lifetime for fluorescent blue. The efficiency is also the highest recorded for a blue polyfluorene material at 10cd/A.

The new blue material yields very good color values and efficiency. The OLED industry has come to regard progress on blue materials as a key indicator, since this performance dictates the range of full color applications which can be implemented. The progress announced today gives a strong indication that the technology is moving rapidly to satisfy the requirements for applications including large display screens.

These new materials are fully printable - a major advantage of polymer OLED technology over other OLED technologies. They are also compatible with each other and could be combined in the same device.

"The progress on red lifetime and efficiency is astonishingly rapid," said David Fyfe, CEO of CDT. "Increasingly, the progress on blue lifetime is building on the synergies arising from both the acquisition of Dow Chemical's P-OLED technology by Sumitomo, and the merging of CDT's and Sumitomo's know-how into Sumation. We are confident of further progress."

Other data released are the lifetimes from higher initial luminance levels of 200, 300 and 400 cd/m2, which for the red material are as follows: 125,000 hours, 55,500 hours and 31,200 hours respectively, and for the blue: 37,500 hours, 16,700 hours and 9,400 hours. Efficiencies are quoted at over 7 cd/A and 10 cd/A for the red and blue respectively.

When "lifetime" is discussed here, it refers to the time taken for the display/pixel to fall to half its initial stated luminance. Lifetime estimates are based on accelerated testing of simple test devices at several very high initial luminance levels, and use of these data to calculate predicted lifetimes at lower brightness levels. Data are presented subject to experimental error.

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