External coupling in organic light-emitting devices.

摘要

This work revolves around organic light-emitting devices (OLEDs) and its application in information displays. The bulk of the work is devoted to the investigation of light emission and external coupling in OLEDs after the appropriate excitons have been formed. The internally-emitted light can be classified into three modes: externally-emitted, substrate-waveguided, and ITO/organic-waveguided. A combined classical and quantum mechanical microcavity (CCQMM) model was used to calculate the lifetime of the excitons and the distribution of light emission into various modes as a function of the OLED architecture. Bilayer OLEDs with varying emitting layer thicknesses, indium-tin-oxide anode thickness, and index of refraction of the substrate were fabricated on both planar and shaped substrates. Shaped substrates were found to increase the external coupling efficiency by converting some substrate-waveguided modes into external modes. The largest increase were in OLEDs on shaped height index-of-refraction substrates where an increase by a factor of 2.3 in the integrated external emission was measured. The CCQMM model accurately predicts the far-field intensity profile, the edge emission and the increase in external emission due to shaped substrates. Device optimization based on these results is discussed.; The second part of this thesis presents the work on an amorphous silicon thin film transistor (TFT) based active-matrix OLED display pixel. The two-TFT pixels were operated at VGA video rates and pixel luminance adjustment by the data voltage was demonstrated.; The work on patterning OLEDs by lithographically patterning and dry etching the cathodes is present in the last part of this thesis. OLEDs with aluminum cathodes were shown to be compatible with the lithographic process. OLED degradation due to exposure to chlorine or oxygen plasma was quantified by measuring the growth of edge dark rings.