Evaluation of transport properties in poly(3-hexylthiophene) using SCLC method and Controlled - Overflow - Transistor
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Abstract: Since the discovery of conducting polymers in 1977, a new era of research work has escalated, with applications such as transistors, solar cells, logic circuits, sensors, etc. The materials can be chemically modified during their synthesis in order to tailor the desired mechanical, electronic and optical properties of the final product. However, one of the main limitations of organic materials is due to the combination of its low mobility, presence of traps and unbalanced mobilities between positive and negative charge carriers. Several methods have been employed to determine the mobility such as time-of-light, field-effect transistor, etc. The work presented in this thesis focuses on utilizing a simple method called Space-Charge-Limited current (SCLC) to determine the mobility of carriers in poly(3-hexylthiophene) (P3HT). P3HT is one of the most studied organic semiconductor polymer due to its high positive charge carrier mobility, good solubility and processability. Its positive charge carrier mobility has been evaluated by several methods including SCLC. However, the knowledge of its negative charge mobility is limited. In this work, we have investigated both the positive and negative charge carrier mobilities utilizing the SCLC method. Finally, the obtained values are compared to the obtained values by other methods that have already determined both of these mobilities. Further, this work also sheds a new light on further enhancing the applications of low-mobility conducting polymers by using it in simple, cost effective hybrid transistor architecture. This transistor takes the advantage of the low mobility in conducting polymers and involves two regimes of operation at low and high electric field strengths. At low electric field, SCLC regime is formed and at high electric field strength thermionic regime is encountered. To our knowledge, this is one of a kind architecture. The device operation mainly depends upon the properties of the conducting polymer in use.
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