Poly(1,4-phenylene-1,2-diphenylvinylene) and tris(8-quinolinolato)aluminum bilayer light-emitting diodes

✍ Scribed by Yang Yang; Qibing Pei

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 256 KB
• Volume: 8
• Category: Article
• ISSN: 1042-7147
• DOI: 10.1002/(sici)1099-1581(199707)8:7<431::aid-pat668>3.0.co;2-c

✦ Synopsis

A bilayer polymer light-emitting diode has been demonstrated. This bilayer structure is composed of two different materials with nearly identical luminescent spectra, but different band positions. The band structure of one material, poly(1,4-phenylene-1,2-diphenylvinylene), favors hold injection, while the band structure of the other material, tris-(8-quinolinolato)aluminum, favors electron injection. Therefore in this device structure, a heterojunction forms at the bilayer interface. Charges injected from the anode and cathode accumulated at this interface and subsequently radiative recombine. Compared with the single-layer devices made from each of these two materials, the device performance of this bilayer LED is significantly improved owing to this carrier localization. Device quantum efficiency is enhanced by a factor of 20 to reach ~1% photons/electron. Unlike some other bilayer systems, there is no color shift of this bilayer structure, because the luminescent spectra are the same for both materials.