Low voltage operation of large area polymer LEDs

Electroluminescence in conjugated polymers

“…3, an external ef®ciency of about 2 lumens per watt (2 lm W -1 ) has been reported in devices made with ITO/MEH-PPV/Ca (ref. 24). Other early approaches used to increase ef®ciency include the use of copolymers based on PPV with higher luminescence ef®ciencies 15 , and the use of heterostructure devices 16 .…”

“…2) and polyaniline, and such materials have been used as hole-injecting electrodes 37±39 . Several groups have reported not only improved device ef®ciency, but also considerably improved device uniformity and longevity 21,24,40,41 . These doped polymer electrodes have high work functions, thereby providing low barriers for hole injection to the semiconductor layer.…”

Excited state dynamics of organic semi-conducting materials

“…Materials based on poly(p-phenylenevinylene) (PPV) have received considerable attention owing to their favourable luminescent and semi-conducting properties. [17][18][19][20] In recent years, there has been a considerable research effort toward understanding the fundamental photophysical and light harvesting properties of this important polymer; in particular, the more useful solubilised analogues such as poly[2-methoxy-5-(2 0 -ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) have been of particular interest. [21][22][23][24][25] In conjugated polymers, a number of competing exciton relaxation pathways are accessible following photoexcitation, oen leading to complex photophysical behavior.…”

Aggregation Quenching of Luminescence in Electroluminescent Conjugated Polymers

“…Organic materials have matured to the point where it appears probable they will be used for many electroluminescent display applications. − Luminescence quantum yield is a critical issue in successful design of systems for this purpose. Photoluminescence quantum yields approaching unity are obtainable with evaporable dyes dilutely doped into thin-film host matrixes as is the case for coumarin dyes in 8-tris hydroxyquinolinealuminum (Alq 3 ). , Even though conjugated polymers suffer from considerably lower photoluminescence quantum efficiency, they remain interesting as electroluminescent materials because they promise to have superior processing and thermal properties.…”