We report on AlGaN/GaN heterostructures ultraviolet (UV) p–i–n photodetectors (PDs) in which generationrecombination and tunneling currents dominate PD leakage at high reverse voltage. At low voltages, the shunt current related to threading dislocations dominate PD leakage. The PD exhibits a narrow bandpass spectral responsivity characteristics from 320 to 360 nm, a zero bias peak responsivity 0.155 A/W at 360 nm, which corresponding to a quantum efficiency of 53%. Additionally, the effect of polarization effect on responsivity of the PD have been investigated.
Organic light-emitting devices (OLEDs) with stable white light emitting were fabricated by using exciton adjusting layer (EAL) inserted between dual emitting layers (EMLs). Three charge transport materials with different characteristics were chosen as EAL, including 4,7-diphenyl-1,1′-phenanthroline (Bphen), N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) and N,N′-dicarbazolyl-3,5-benzene (mCP). Device structure was given as: ITO/NPB (30 nm)/mCP: (t-bt)2Ir(acac) (2 nm, 4 wt.%)/EALs/ mCP: Firpic (12 nm, 10 wt.%)/Bphen (35 nm)/Mg: Ag (100 nm). The results showed that, compared with device without EAL, the devices employed EAL yielded high device performance as well as favorable luminescence property and stable white emission. For the device with mCP EAL, the maximum brightness of 24700cd/m2 and current efficiency of 14.5 cd/A were obtained, while the CIE coordinates of device changed from (0.33, 0.35) to (0.35, 0.36) with the bias voltage increasing from 5 V to 12 V. It was suggested that by incorporating EAL in OLEDs, the charge carrier recombination zone was broadened, and the balance of electron-hole was improved between EMLs.
Double emitting layer (yellow and blue) phosphorescent organic light emitting devices (OLEDs) were fabricated using different materials as the interlayer. The structure of the devices is ITO/NPB/(t-bt)2Ir(acac)/interlayer/BCP: FIr6/Bphen/Mg:Ag. Interlayers are mCP, TPBi, and TAPC, respectively. Comparing three kinds of interlayer, the luminescence characteristics of the devices are investigated. The results show that the current efficiency and the brightness are greatly improved because of the application of interlayer. Using the mCP as the interlayer, we obtained the maximum current efficiency of 39 cd/A and the maximum brightness of 18360 cd/m2, the color stability is also be enhanced.
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