Study Of Optical And Electrical Properties Of The Polymer Semiconductor Films And Devices

Semiconducting polymers are a novel class of materials that combine the optical and electronic properties of semiconductors with the processing advantages of polymers. These materials hold great promise for a wide range of applications in optoelectronic devices, such as light emitting diodes, laser diodes, solar cell and thin film transistors.Optical and electronic properties of polymer films are fundamentals of further practical devices. The work at hand presents a comprehensive investigation of the optical performance of the film form of conjugated polymers and the photonic devices based on polymer thin films. At first, the luminescence properties of conjugated polymer thin films and molecularly doped polymer films are experimentally studied. Then the optical characteristics of top-emitting light emitting diodes and resonant photodiodes with asymmetric microcavity structures are theoretically investigated and simulated, and an optimal configuration is proposed.The absorption and photoluminescenc properties of MO-PPV thin films are investigated through spectral analysis and microcopical observation. The effects from surface morphology, film conformation, molecular structure and annealing treatment on luminescence performance are compared and analyzied. Especially the possibility of the emission from the aggregates and excimers formed in film samples are discussed and distinguished through transition theory and experiment results.Due to the advantages of small self-absorption, narrower spectral width and adjustable emission spectra, molecularly doped polymers are more attractive than pure polymer thin films for practical applications. In this work, the electroluminescenc and photoluminescence in a novel doped system, PVK films doped with TMEP molecules, are investigated detailedly. The role of Forster energy transfer and carrier trapping mechanisms in this doped system is compared and identified clearly, and the doped polymer light emitting diodes with high electroluminescenc efficiency are fabricated.As to polymer photonic devices, their optimized performance is important as wellas the optical properties of polymer films. The work of the last part of this thesis focuses on theoretical analysis and optimization of the organic/polymeric optoelectronic devices with asymmetric microcavity structurers: top-emitting light emitting diodes (TELED's) and photodiodes. A more reasonable criterion for semitransperant cathode in TELED's is proposed, in which the emission characteristics of the active layer is considered. Based on this, the extracting efficiency of the device is optimized. In the analysis about microcavity-enhanced photodiodes (MEPD's), analytical expression of the resonant field in the cavity including the incident angle effect is presented. Then the variance of the resonant absorption and the quantum efficiency in MEPD's and an optimal cavity configuration can be obtained within a widely incident angle range.