Time-independent charge carrier mobility in a model polymer: fullerene organic solar cell

Journal Publication ResearchOnline@JCU
Philippa, Bronson;Vijila, Chellappan;White, Ronald D.;Sonar, Prashant;Burn, Paul L.;Meredith, Paul;Pivrikas, Almantas
Abstract

The technique of photo-CELIV (charge extraction by linearly increasing voltage) is one of the more straightforward and popular approaches to measure the faster carrier mobility in measurement geometries that are relevant for operational solar cells and other optoelectronic devices. It has been used to demonstrate a time-dependent photocarrier mobility in pristine polymers, attributed to energetic relaxation within the density of states. Conversely, in solar cell blends, the presence or absence of such energetic relaxation on transport timescales remains under debate. We developed a complete numerical model and performed photo-CELIV experiments on the model high efficiency organic solar cell blend poly[3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene] (PDPP-TNT):[6,6]-phenyl-C71-butyric-acid-methyl-ester (PC70BM). In the studied solar cells a constant, time-independent mobility on the scale relevant to charge extraction was observed, where thermalisation of photocarriers occurs on time scales much shorter than the transit time. Therefore, photocarrier relaxation effects are insignificant for charge transport in these efficient photovoltaic devices.

Journal

ORGANIC ELECTRONICS

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Volume

16

ISBN/ISSN

1878-5530

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Pages Count

7

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Publisher

Elsevier

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DOI

10.1016/j.orgel.2014.10.047