Is there a way to pair the many colors produced by small-molecule OLEDs with the economic benefits of the spin solution coating used in PLEDs? One recent exciting development builds on the successful application of these phosphorescent materials to potentially do just that. Workers at the University of Oxford, the University of St. Andrews and OpSys in Oxford, England, have synthesized molecules known as dendrimers that may prove to combine the desirable aspects of small molecules and polymers. In a dendrimer, a phosphorescent molecule serves as the core around which layers of branching ring structures are bonded, forming a large molecular ball. If the branching elements are suitably chosen, these molecules can be dissolved, and films can be formed by spin coating and baking, as with polymer materials. Already dendrimer devices have yielded very high luminous efficiencies (more than 50 candelas per ampere and 40 lumens per watt).

   
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