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Achieving a Stable Time Response in Polymeric Radiation Sensors under Charge Injection by X-rays

Intaniwet, A, Mills, CA, Sellin, PJ, Shkunov, M and Keddie, JL (2010) Achieving a Stable Time Response in Polymeric Radiation Sensors under Charge Injection by X-rays ACS APPL MATER INTER, 2 (6). 1692 - 1699. ISSN 1944-8244

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Abstract

Existing inorganic materials for radiation sensors suffer from several drawbacks, including their inability to cover large curved areas, lack of tissue equivalence toxicity, and mechanical inflexibility. As an alternative to inorganics, poly(triarylamine) (PTAA) diodes have been evaluated for their suitability for detecting radiation via the direct creation of X-ray induced photocurrents. A single layer of PTAA is deposited on indium tin oxide (ITO) substrates, with top electrodes selected from Al, Au, Ni, and Pd. The choice of metal electrode has a pronounced effect on the performance of the device; there is a direct correlation between the diode rectification factor and the metal-PTAA barrier height. A diode with an Al contact shows the highest quality of rectifying junction, and it produces a high X-ray photocurrent (several nA) that is stable during continuous exposure to 50 kV Mo K alpha X-radiation over long time scales, combined with a high signal-to-noise ratio with fast response times of less than 0.25 s. Diodes with a low band gap, 'Ohmic' contact, such as ITO/PTAA/Au, show a slow transient response. This result can be explained by the build-up of space charge at the metal-PTAA interface, caused by a high level of charge injection due to X-ray-induced carriers. These data provide new insights into the optimum selection of metals for Schottky contacts on organic materials, with wider applications in light sensors and photovoltaic devices.

Item Type: Article
Uncontrolled Keywords: sensor, conjugated polymer, organic electronics, charge transport, rectification, poly(triarylamine) (PTAA), ORGANIC SEMICONDUCTORS, TRIARYLAMINES, DEVICES
Divisions: Faculty of Engineering and Physical Sciences > Physics
Depositing User: Symplectic Elements
Date Deposited: 03 Jun 2011 12:25
Last Modified: 23 Sep 2013 18:41
URI: http://epubs.surrey.ac.uk/id/eprint/2962

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