Date of Award
Doctor of Philosophy
Physics and Astronomy
The Origin of the PLDMR enhancing signal and various aspects of the device physics of small molecular doped PLEDs were described and discussed. The difference between the delay model and the quenching model was explained. The microwave- and laser-modulation-frequency dependence of the PLDMR and DM-PLDMR, respectively, in MEH-PPV, invalidated the delay models, questioning reports of SE yields exceeding 25% in fluorescent OLEDs. Rather, the results were consistent with the quenching model where SEs are annihilated by TEs and polarons. For the device, the proper procedure for the treatment of the PEDOT/PSS layer with EG was suggested and a 10 fold enhancement was shown. The radiance of the device showed ~10 fold improvement with an addition of EG treated PEDOT/PSS layer and ~5 fold with 12 nm thick BCP and Alga layer. With both layers, a 45 fold improvement in the brightness, 8 fold in the external quantum efficiency, and 7 fold in the power efficiency were achieved. Also, for WOLED, the addition of the DPVBi layer on top of the DPVBi doped PVK improved device performance ~3 fold by reducing quenching by the cathode. The optimized device structure was suggested and tested. They exhibited white emission with a brightness of 9000 Cd/m2 at a current density of 1000 mA/cm 2 and the maximal quantum efficiency of 2.2% at 16 V.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Lee, Moon-Ky, "Optically detected magnetic resonance (ODMR) measurements on conjugated polymers and studies of poly-(n-Vinyl Carbazole) (PVK) based LEDs" (2005). Retrospective Theses and Dissertations. 1750.