White emission from a polymer blend light-emitting diode by incomplete cascade energy transfer

Abstract

White light emission was obtained from a polymer light-emitting diode (LED) made of a ternary polymer blend comprised of poly(9-vinylcarbazole) (PVK), poly(9,9'-dihexlyfluorene-2,7-divinylene-m-phenylenevinylene-stat-p-phenylenevinylene) (CPDHFPV), and poly[2-methoxy-5-(2'-(ethyl-hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) (19:1:1 by wt.). Incomplete cascade energy transfer was employed to obtain white emission from the polymer blend LED. Compatibility between PVK and CPDHFPV facilitated the Forster-type energy transfer from PVK to CPDHFPV. However, poor compatibility between CPDHFPV and MEH-PPV resulted in a partial energy transfer between the polymers causing the blend to emit two colors simultaneously. Consequently, pure white color near CIE coordinate (0.33, 0.33) could be obtained with a low sensitivity to the drive voltage.