Solid-state near infrared emitting platinum(ii) complexes as either an ultrathin or singly doped phosphorescence emitting layer in hybrid white OLEDs exhibiting high efficiency and colour rendering index

Abstract

Two solid-state near infrared (NIR) emitting platinum complexes, PBSNND and AtFNND, have been employed together with classical blue fluorescent 4P-NPD in the fabrication of hybrid white OLEDs. Through an ultrathin emitting layer approach, we have successfully achieved a dual emission, yellow and deep red/NIR electroluminescence (EL) for the PBSNND-based hybrid WOLEDs. The ideal EL performance was obtained from a hybrid WOLED with a 1.0 nm ultrathin phosphorescence emitting layer and a layer of 4P-NPD (2.5 nm) in front of TPBI, the electron transporting layer of the device (Hyb W1). The Hyb W1 exhibited a warm white EL, CIE_x,y (0.41, 0.31), a high colour rendering index (CRI) of 86, and an external quantum efficiency (EQE) as high as 12.9%. Dissimilarly, when a singly doped phosphorescence emitting layer was adopted, a dual emission, green and deep red/NIR electroluminescence (EL) was obtained for the AtFNND-based hybrid WOLEDs. With an AtFNND dopant concentration of 5 or 7 wt%, a purplish blue white EL, CIE_x,y (0.30, 0.31), a high colour rendering index (CRI) of 84, and an external quantum efficiency (EQE) as high as 10.5%; an authentic white EL, CIE_x,y (0.35, 0.32), a very high colour rendering index (CRI) of 88, and an external quantum efficiency (EQE) as high as 13.7% have been achieved for device Hyb W2 and Hyb W3, respectively.