White organic light-emitting devices with CdSe/ZnS quantum dots as a red emitter

Abstract

White hybrid organic/inorganic light-emitting devices (LEDs) have been fabricated by using stable red-emitting CdSe/ZnS core-shell quantum dots (QDs) covered with a trioctylphosphine oxide organic ligand. The device-active structure consists in a host/guest system with a blue-emitting poly[(9,9-dihexyloxyfluoren-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy}phenylen-1,4-diyl)] (PFH-MEH) polymer doped with red-emitting QDs and a green emitting metal chelate complex Alq3, with improved electron injection and transfer properties. A fairly pure white OLED with Commission Internationale de l’Eclairage coordinates of (0.30,0.33) is fabricated by accurate control of the Förster energy and charge-transfer mechanisms between the different device constituents obtained by tuning the concentration ratio of the QDs/PFH-MEH blend. In particular, charge-transfer processes to CdSe/ZnS core-shell quantum dots are found to be the key element for well-balanced white emission. Maximum external quantum efficiency up to 0.24% at 1mAcm−2 and 11 V in air atmosphere are reported, showing that hybrid LEDs can be a promising route towards more stable and efficient light-emitting devices for lighting applications.