Organic waveguides, amplified spontaneous

The last example of this section deals with the optical function of hole-transport layers. In OLEDs some light is waveguided in the combined anode/organic layers due to total internal reflection [44], By increasing the thickness of the hole conductor the emitter can be optically decoupled from the contact. In a series of devices with increasing thickness of the hole conductor, deposited subsequently from solution, it was shown that a HTL thickness larger than 300 nm was necessary to accomplish this. As a very sensitive measure the threshold of amplified spontaneous emission (ASE) was used (Fig. 9.18, [45]). This is an important result with respect to a potential electrically driven organic laser diode. 

Figure 19 (a, b) Waveguide architectures and (c) the chemical structure of the polymer and the analytes. SOP, semiconducting organic polymers ASE, amplified spontaneous emission DFB, distributed feedback ITO, Indium tin oxide LUMO, lowest unoccupied molecular orbital HOMO, highest occupied molecular orbital DAG, diacylglycerol Al, Aluminium IL, insertion loss PET, Polyethylene terephthalate PEN, Polyethylene naphthalate. Reproduced with permission from Rose, A. Zhu, Z. G. etal. Nature 200B, 434 (7035), 876-879. ... 

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