High-efficiency new polymer light-emitting diodes with a stabilized blue emission

Abstract

Conjugated polymers with a stabilized blue emission are of importance for the realization of full-color displays using polymer light-emitting diodes. We report a new class of blue-emitting polymers utilizing a new back-bone, poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta [def] phenanthrene)) (PCPP). This material emits a stabilized, efficient blue-electroluminescence (EL) without exhibiting any peak in the long wavelength region (green region) even after prolonged annealing for 18 hours at an elevated temperature of 150°C in air. This attributes to the chemical structure of this new polymer. The backbone of PCPP intrinsically inhibits the formation of the keto-defects mainly responsible for the degradation to green color in typical poly(fluorine) type materials, thereby stabilizing the blue EL emission in the devices.