ABSTRACT
In 1977, with the report of high conductivity in dope polyacetylene [1,2], interest in the field of
conductive polymers surged. While this research eventually led to Professors Heeger, MacDiarmid,
and Shirakawa receiving the Noble Prize in Chemistry, commercialization of conductive polymers was
impeded by poor stability, and research activity decreased until a 1990 Nature paper by Friend and
colleagues was published [3], which reported on a light-emitting diode with poly(p-phenylenevinylene)
(PPV) as the light-emitting layer. The efficiency of this device was low at 0.01% internal quantum
efficiency [3]; the PPV used as the electroluminescent (EL) layer emitted in the green and was
synthesized via a precursor route, since it was not solution-processable. Since then there have been
considerable advances in polymer design and devices. Phillips introduced an electric shaver with a
polymeric light-emitting diode (PLED) display in 2002 and reported efficiencies of 14 Cd=A in the green
with lifetimes in excess of 104 h [4]. Other corporations are considering PLEDs for commercialization in
displays, although at this time evaporated small molecule organic light-emitting diodes (SMOLEDs)
have captured more of the market. Some of the advantages that PLEDs have over liquid crystal displays
are that PLEDs do not require a backlight and need fewer or no filters. They have faster response times,
an advantage for video, a 1808 viewing angle, may be printed [5,6], and can be made on flexible
substrates [7], although encapsulating a PLED made on a flexible substrate to ensure long life is still a
major challenge. A challenge facing the field is, however, to improve lifetime of the PLEDs, particularly
for blue-emitting devices [7].
