Balanced Carrier Mobilities: Not a Necessary Condition for High‐Efficiency Thin Organic Solar Cells as Determined by MIS‐CELIV |
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| Authors: | Ardalan Armin Gytis Juska Mujeeb Ullah Marappan Velusamy Paul L. Burn Paul Meredith Almantas Pivrikas |
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| Affiliation: | 1. Centre For Organic Photonics & Electronics (COPE) School of Chemistry and Molecular Biosciences and School of Mathematics and Physics, The University of Queensland, Brisbane, Australia;2. Department of Solid State Electronics, Vilnius University, Vilnius, Lithuania |
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| Abstract: | A novel technique based upon injection‐charge extraction by linearly increasing voltage (i‐CELIV) in a metal‐insulator‐semiconductor (MIS) diode structure is described for studying charge transport in organic semiconductors. The technique (MIS‐CELIV) allows selective measurement of both electron and hole mobilities of organic solar cells with active layers thicknesses representative of operational devices. The method is used to study the model high efficiency bulk heterojunction combination poly[N‐9′′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole)] (PCDTBT) and [6,6]‐phenyl C70‐butyric acid methyl ester (PC70BM) at various blend ratios. The absence of bipolar transport in PCDTBT‐and‐PC70BM‐only diodes is shown and strongly imbalanced carrier mobility is found in the most efficient “optimized” blend ratios. The mobility measurements are correlated with overall device performance and it is found that balanced and high charge carrier mobility are not necessarily required for high efficiencies in thin film organic solar cells. |
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| Keywords: | organic solar cells charge carrier mobility field‐effect transistors internal quantum efficiency |
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