The Effect of Morphology on Charge Transport Properties in OPVs

ORAL

Abstract

The Organic Photovoltaic (OPV) field is rapidly advancing, however several important issues regarding the device physics in these systems remain~unresolved. We investigated the relationship between morphology and charge transport properties in OPV materials. To do this, we created devices with poly 3-hexothyophene (P3HT) of a range of molecular weights (from 13kDa to 331kDa). These various molecular weights cause the films to have different morphologies. The low molecular weight P3HT forms semi-crystalline domains, as the molecular weight increases, amorphous regions appear connecting and surrounding the semi-crystalline domains. The devices were measured using the Charge Extraction by Linearly Increasing Voltage (CELIV) technique in order to determine the charge carrier mobility and recombination rate of the various P3HTs. We found that while the recombination rate decreases with increasing molecular weight, the mobility peaked at around 47kDa. We believe that the decrease in recombination is due to charge dissociation of electrons and holes into separate regions of the film. While the lower recombination rate from the separate amorphous and semi-crystalline domains raises the mobility, the increasing amount of amorphous material at larger molecular weights causes a decrease in mobility, resulting in the observed mobility peak.

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Authors

  • Alex Dixon

    University of Denver

  • Benjamin Bloom

    Department of Physics, University of Arizona, Tucson, AZ, National Institute for Materials Science, Tsukuba, Japan, The University of Electro-Communications, Tokyo, Langmuir Laboratory, New Mexico Tech, The University of Arizona, Brigham Young University, Department of Physics Colorado State University, Colorado School of Mines, National Renewable Energy Laboratory, University of Colorado Boulder, Principal Investigator, Graduate Student, Colorado State University, SSRL, SLAC, Department of Chemistry and Biochemistry, Brigham Young University, Department of Physics and Astronomy, Brigham Young University, National Tsing Hua University, Hsinchu, Taiwan, Colorado State Univ, JILA, University of Colorado at Boulder, NIST, JILA, University of Colorado at Boulder, Heinrich-Heine-Universitat, Department of Physics, University of Colorado Denver, Denver, CO 80217, Biomedical Engineering, University of Texas at Austin, Austin, TX, The University Centre in Svalbard, Utah State University, Utah Valley University, New Mexico State University, The George Washington University Nuclear Physics Research Group, Institute for Nuclear Physics at the Johannes Gutenberg University of Mainz, None, Colorado State Engineering Research Center, St. Petersburg Electrotechnical University in Saint Petersburg, Russia, University of California San Diego, Argonne National Laboratory, Los Alamos National Laboratory, Imperial College London, Space Dynamics Lab, Utah State University, Physics and CASS, Utah State University, Department of Chemistry, Colorado State University, Fort Collins, CO 80523, Department of Physics, Colorado State University, Fort Collins, CO 80523, Dept. of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder, Dept. of Physics and Astronomy, University of Denver, CU Boulder, RASEI, NREL, University of Colorado, Rutgers, UTK, Joint Institute for Heavy Ion Research \& ORNL, University of Guelph, Insitituto de Estructura de la Materia, University of Toronto, INFN Laboratori Nazionali del Sud, University of York, University of Surrey, TRIUMF, Simon Frasier University, Universdad de Sevilla, Simon Fraser University, Univ of Utah, Univ of Wyoming, New Mexico Tech, GLOBALFOUNDRIES, IBM Systems and Technology Group, IBM Research Division, Irvine Valley College, University of Colorado - Boulder, Department of Physics, Arizona State University, Tempe, AZ, Department of Physics, New Mexico State University, Las Cruces, NM, Department of Physics, University of Michigan, Flint, MI, High Altitude Observatory, JILA, University of Colorado

  • Benjamin Bloom

    Department of Physics, University of Arizona, Tucson, AZ, National Institute for Materials Science, Tsukuba, Japan, The University of Electro-Communications, Tokyo, Langmuir Laboratory, New Mexico Tech, The University of Arizona, Brigham Young University, Department of Physics Colorado State University, Colorado School of Mines, National Renewable Energy Laboratory, University of Colorado Boulder, Principal Investigator, Graduate Student, Colorado State University, SSRL, SLAC, Department of Chemistry and Biochemistry, Brigham Young University, Department of Physics and Astronomy, Brigham Young University, National Tsing Hua University, Hsinchu, Taiwan, Colorado State Univ, JILA, University of Colorado at Boulder, NIST, JILA, University of Colorado at Boulder, Heinrich-Heine-Universitat, Department of Physics, University of Colorado Denver, Denver, CO 80217, Biomedical Engineering, University of Texas at Austin, Austin, TX, The University Centre in Svalbard, Utah State University, Utah Valley University, New Mexico State University, The George Washington University Nuclear Physics Research Group, Institute for Nuclear Physics at the Johannes Gutenberg University of Mainz, None, Colorado State Engineering Research Center, St. Petersburg Electrotechnical University in Saint Petersburg, Russia, University of California San Diego, Argonne National Laboratory, Los Alamos National Laboratory, Imperial College London, Space Dynamics Lab, Utah State University, Physics and CASS, Utah State University, Department of Chemistry, Colorado State University, Fort Collins, CO 80523, Department of Physics, Colorado State University, Fort Collins, CO 80523, Dept. of Electrical, Computer, and Energy Engineering, University of Colorado at Boulder, Dept. of Physics and Astronomy, University of Denver, CU Boulder, RASEI, NREL, University of Colorado, Rutgers, UTK, Joint Institute for Heavy Ion Research \& ORNL, University of Guelph, Insitituto de Estructura de la Materia, University of Toronto, INFN Laboratori Nazionali del Sud, University of York, University of Surrey, TRIUMF, Simon Frasier University, Universdad de Sevilla, Simon Fraser University, Univ of Utah, Univ of Wyoming, New Mexico Tech, GLOBALFOUNDRIES, IBM Systems and Technology Group, IBM Research Division, Irvine Valley College, University of Colorado - Boulder, Department of Physics, Arizona State University, Tempe, AZ, Department of Physics, New Mexico State University, Las Cruces, NM, Department of Physics, University of Michigan, Flint, MI, High Altitude Observatory, JILA, University of Colorado