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Keywords: organic semiconductor, time-of-flight, charge carrier mobility, solid processing, large crystal
Published in RUNG: 28.02.2023; Views: 2467; Downloads: 84
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Abstract: The focus of this diploma seminar is to describe different types of charge transport theory and models used for finding mobility in semiconductors, more specifically focused on P3HT thin-film organic semiconductor. It also describes the time-of-flight method, which was used to measure the experimental data for P3HT with time dependent current I(t) curve. Another data set was obtained by performing Kinetic Monte Carlo (KMC) simulations using Miller-Abrahams hopping formalism. KMC was used to determine the material disorder, simulate I(t) curve and transit time for every charge carrier. Simulated data, different transit times and mobilities were then finally compared with experimental, in order to find agreements between the two.
Keywords: charge transport, P3HT, thin-film organic semiconductor
Published in RUNG: 15.09.2021; Views: 4163; Downloads: 0
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Abstract: Poly(3-hexylthiophene) (P3HT) is an organic semiconductor material that is widely studied in the photovoltaics and transistor fields of research. The polymer exhibits a relatively high charge carrier mobility when the molecules are ordered in a crystalline way. In this case the material exhibits a fibril-like morphology, which is usually studied by atomic force microscopy (AFM). Previous studies show that blending P3HT with graphene can further improve the charge carrier transport properties of the film. In this experiment, the scanning electron microscope (SEM) has been chosen, due to its practical aspects such as speed of operation and ease of use. Three sets of samples have been analyzed, containing films made of P3HT+graphene blends at different concentrations. The aims of the experiment are: i) to find good conditions for the observation of the morphology features of the film ii) to perform a morphological analysis of the surface of three sets of samples containing both pure P3HT, and P3HT+graphene blend, and possibly to highlight correlation between morpholgy and the charge transport properties. Surface analysis is done by detecting the secondary electron (SE) emission, which is sensitive to topographical features of the surface. Good observation conditions were established by coating the specimen with a thin layer of conductive coating, using a high energy beam (30 keV), and tilting the sample to an angle (30 ◦ ). In two out of three of the analyzed pure P3HT films, the presence of fibrilles indicated a possibly good charge mobility, which has been confirmed by electrical measurements using time-of-flight photoconductivity method (TOF). The presence of graphene has only slightly modified morphology of the film. Features of graphene flakes, which lie flat in the film, have been observed such as flake edges and folds. The flakes are homogeneously dispersed in the film without forming any connected network. TOF measurements have shown an increase in mobility of the charge carriers in the P3HT+graphene film.
Keywords: scanning electron microscope, organic semiconductor thin film, P3HT, graphene, morphology
Published in RUNG: 01.12.2016; Views: 8754; Downloads: 175
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