Rathi, Sonika and Chauhan, Gayatri and Gupta, Saral K. and Srivastava, Ritu and Singh, Amarjeet (2017) Analysis of Blockade in Charge Transport Across Polymeric Heterojunctions as a Function of Thermal Annealing: A Different Perspective. Journal of Electronic Materials , 46 (2). pp. 1235-1247. ISSN 0361-5235

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A blend of poly(3-hexylthiophene-2,5diyl) (P3HT) and [6,6]-phenyl C-61 butyric acid methyl ester (PCBM) is popularly used as an active medium in polymeric solar devices. According to the most recent understanding, the blend is a three-phase system contrary to its earlier understanding of two-phase bicontinuous network. We have synthesized a P3HT-PCBM based layered heterostructure system by spin coating and thermal vacuum evaporations. Current density (J) was measured as a function of applied electric field (E) across the system bound between two metal electrodes. J-E relations were analyzed into the backdrop of space charge limited current model and Schottky model. The later was used to predict dc-dielectric constants from the linear slopes of ln (J) versus E (1/2). The curves were not monotonously linear, but observe a knee-bend separating into two linear segments for each curve. Thermal annealing from 40A degrees C to 80A degrees C was used as an activation tool for driving changes in the internal morphology via inter-diffusion of polymers and current measurements were performed at room temperature after each annealing. At the last stage of annealing the two linear slopes were highly distinct. The presence of sharp knee-bend results in approximately 20 times jump in dielectric constant as a function of electric field. Such high jumps in dielectric constant illustrate the potential for switching applications and charge storage. The high dielectric constants can be understood in terms of space charge polarization due to isolated domains which hindrance to charge transport. The high dielectric constants were confirmed by another experiment of capacitance measurements of a different set of similar samples. A study of thermal evolution of internal morphology was also carried out using x-ray diffraction and scanning electron microscopy techniques to correlate the morphological changes with the transport properties.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s Institute of Electrical and Electronics Engineers.
Subjects: Engineering > Electronics and Electrical Engineering
Materials Science
Applied Physics/Condensed Matter
Depositing User: Users 27 not found.
Date Deposited: 14 Aug 2018 10:50
Last Modified: 14 Aug 2018 10:50
URI: http://npl.csircentral.net/id/eprint/2602

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