Phosphorescent organic light-emitting diodes (PhOLEDs) have been extensively explored over the last decade for developing highly efficient displays and solid-state lighting. Current high-performance PhOLEDs have been largely fabricated by vacuum-deposition of small molecules involving sequential thermal evaporation to obtain multilayered structures. We report high-performance blue, green, red and white PhOLEDs achieved by a new orthogonal solution-processing of new and commercial electron transport materials (ETMs). We demonstrate that orthogonal solution-processed electron-transport layers (ETLs) of wide-energy-gap ETMs exhibit a unique surface morphology which facilitates enhanced charge-injection and transport from the cathode. Furthermore, we show that organic small-molecule ETMs can be n-doped with alkali metal salts (e.g. Cs2CO3, Li2CO3) by orthogonal solution-processing to achieve high-performance PhOLEDs. For example, blue PhOLEDs with solution-processed ETL doped with Cs2CO3 show a luminous efficiency of 38 cd/A with an external quantum efficiency of 19.0%, which is the best performance observed to date in solution-processed blue PhOLEDs. We have also developed new high-triplet-energy (ET > 2.8 eV) materials with good electron-transport and exciton-blocking properties for high performance blue and white PhOLEDs.

Solution processed high-performance phosphorescent OLEDs for displays and lighting

246th National Meeting (2013)

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