Low Molecular Weight Organic LED

The main starting point for thin-fihn low molecular weight materials was the work reported by Ching W. Tang and Steven van Slyke of Kodak in 1987, when they described the green electrolnminescence obtained from a thin film of vapour deposited aluminium tris(8-hydroxyquinoline) (Alq). ° Since that time the development of multilayer device structures and several new important classes of organic EL materials has led to snbstantial improvements and to the commercial development of display technologies based on this system.  

A typical vaponr deposited EL device consists of a glass snbstrate coated with a conducting transparent indinm tin oxide electrode, on top of which is a 100-500 A hole transport layer (HTL), followed by a thin (= 100 A) light emitting layer (EML), then a 100-500 A electron transport layer (ETL) and finally a cathode of an alloy such as Mg Ag. This is illustrated in Fignre 3.32. 

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