tailieunhanh - Organic Light Emitting Diode Part 7

Tham khảo tài liệu 'organic light emitting diode part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Solution Processable Ionic p-i-n Organic Light- Emitting Diodes 113 Fig. 6. Upper A photograph of the operating sample device right and reference device left . Lower Normalized EL spectra for the operating sample device and reference device. Park et al. 2008 The EL operation was observed for the fabricated devices with the naked eye. Figure 6 a shows a photograph of the operating devices. For clear comparison we took a photograph of the device operation under the same bias of 11 V. The figure clearly demonstrates that there is bright and homogeneous EL emission from the active area in the sample device while there is relatively weak emission from the active area in the reference device. Next we observed the EL spectra of the devices. As shown in Fig. 6 b the emission spectra of the sample devices are almost identical to those of the reference devices there is a spectral peak wavelength of 516 nm with FWHM of 70 nm. These results for the EL spectra indicate that the doped organic salt does not interfere with the energy band gap of the organic materials. It is likely that the slight increase in the shoulder luminescence near 530 nm for the sample device arises from the more phosphorescent sites at the excited energy level Xie et al. 2001 . It is noted that the CIE coordinate of x y for the sample devices is independent of current density. Next we observed the dynamic responses of the operating devices. As shown in Fig. 7 the observed dynamic responses of the sample device are nearly identical to those of the reference device the rising time and falling time are about 10 ps and 9 ps respectively. These fast responses of the sample device indicate that the separated ions remain at the contacts in a stable fashion and the ions at the interfaces can increase the charge injection into the organic layer. In other words at the ITO anode contact the 114 Organic Light Emitting Diode accumulated negative BF4- ions can bend the energy level and reduce the tunneling .