Shumei Yue

Low-voltage, high-efficiency nondoped phosphorescent organic light-emitting devices with double-quantum-well structure

Low-voltage and high-efficiency nondoped phosphorescent organic light-emitting devices are fabricated by introducing a simple triplet double-quantum-well structure with an Ir(III) complex as potential well layer (PWL) and emitting layer (EML). The effects of various potential barrier layer (PBL) on device performances are discussed. Remarkably, the device with 1,3,5-tris(N-phenyl-benzimidazol-2-yl)benzene (TPBi) as PBL shows a low turn-on voltage of 2.30 V, a maximum power efficiency of 30.5 lm/W at 2.65 V and 24.5 lm/W with 1000 cd/m2 at 3.75 V. We attribute these to the efficient carrier/exciton confinement function of TPBi and the improvement of carrier injection/balance in PWL/EML by self-balancing effect.

Enhanced Red Phosphorescence in MgGeO3 : Mn2 + by Addition of Yb3 + Ions

Enhancement of the 4 T 1g ( 4 G) → 6 A 1g ( 6 S) red emission of MgGeO 3 :1% Mn 2+ with addition of Yb 2 O 3 is reported. The initial phosphorescence in the Yb 2 O 3 codoped sample is an order of magnitude stronger than that of the Yb 2 O 3 -free sample. Thermoluminescence spectra indicate that the introduction of Yb 3+ into the host produces traps with a suitable depth, resulting in the enhanced red phosphorescence of Mn 2+ . The possible mechanism for this phenomenon is explained by a competitive trapping model.