Tuesday, June 29, 2010

Hybrid Polymer Light-Emitting Devices Combine Characteristics of PLEDs and PLECs

The Regents of the University of California (Oakland, CA) earned U.S. Patent 7,745,520 for hybrid polymer light-emitting devices that overcomes previous disadvantages of polymer light emitting diodes (PLEDs) and polymer light-emitting electrochemical cells (PLECs). 

Inventors Yan Shao, Guillermo C. Bazan and Alan J. Heeger  developed light-emitting devices that incorporate a soluble phenyl-substituted poly(para-phenylene vinylene) (PPV) copolymer ("superyellow") which is used as the host light-emitting polymer and methyltrioctylammonium trifluoromethanesulfonate, an ionic liquid is used to introduce a dilute concentration of mobile ions into the emitting polymer layer. These mixtures and devices incorporating them are able to combine some of the characteristics of polymer light emitting diodes (PLEDs) and polymer light-emitting electrochemical cells (PLECs).

Polymer light-emitting devices have been divided into two general types: polymer light-emitting diodes (PLEDs) and polymer light-emitting electrochemical cells (PLECs). The advantages for PLEDs include fast response and relatively long operating lifetime (with proper packaging). However, low work function cathodes and/or thin interfacial layers (e.g. LiF) between the metal and the emitting polymer layer are required. In contrast, PLECs have relatively low turn-on voltages (approximately equal to the band gap of the luminescent semiconducting polymer), and low work function metals are not required. 

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