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Effect of Solvent Additive on Generation, Recombination, and Extraction in PTB7:PCBM Solar Cells: A Conclusive Experimental and Numerical Simulation Study

  • Time-delayed collection field (TDCF), bias-assisted charge extraction (BACE), and space charge-limited current (SCLC) measurements are combined with complete numerical device simulations to unveil the effect of the solvent additive 1,8-diiodooctane (DIO) on the performance of PTB7:PCBM bulk heterojunction solar cells. DIO is shown to increase the charge generation rate, reduce geminate and bimolecular recombination, and increase the electron mobility. In total, the reduction of loss currents by processing with the additive raises the power conversion efficiency of the PTB7:PCBM blend by a factor of almost three. The lower generation rates and higher geminate recombination losses in devices without DIO are consistent with a blend morphology comprising large fullerene clusters embedded within a PTB7-rich matrix, while the low electron mobility suggests that these fullerene clusters are themselves composed of smaller pure fullerene aggregates separated by disordered areas. Our device simulations show unambiguously that the effect of theTime-delayed collection field (TDCF), bias-assisted charge extraction (BACE), and space charge-limited current (SCLC) measurements are combined with complete numerical device simulations to unveil the effect of the solvent additive 1,8-diiodooctane (DIO) on the performance of PTB7:PCBM bulk heterojunction solar cells. DIO is shown to increase the charge generation rate, reduce geminate and bimolecular recombination, and increase the electron mobility. In total, the reduction of loss currents by processing with the additive raises the power conversion efficiency of the PTB7:PCBM blend by a factor of almost three. The lower generation rates and higher geminate recombination losses in devices without DIO are consistent with a blend morphology comprising large fullerene clusters embedded within a PTB7-rich matrix, while the low electron mobility suggests that these fullerene clusters are themselves composed of smaller pure fullerene aggregates separated by disordered areas. Our device simulations show unambiguously that the effect of the additive on the shape of the currentvoltage curve (J-V) cannot be ascribed to the variation of only the mobility, the recombination, or the field dependence of generation. It is only when the changes of all three parameters are taken into account that the simulation matches the experimental J-V characteristics under all illumination conditions and for a wide range of voltages.show moreshow less

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Metadaten
Author:Juliane Kniepert, Ilja Lange, Jan Heidbrink, Jona Kurpiers, Thomas J. K. Brenner, L. Jan Anton Koster, Dieter NeherORCiDGND
DOI:https://doi.org/10.1021/jp512721e
ISSN:1932-7447 (print)
Parent Title (English):The journal of physical chemistry : C, Nanomaterials and interfaces
Publisher:American Chemical Society
Place of publication:Washington
Document Type:Article
Language:English
Year of first Publication:2015
Year of Completion:2015
Release Date:2017/03/27
Volume:119
Issue:15
Pagenumber:11
First Page:8310
Last Page:8320
Funder:German Science Foundation (DFG) within the priority program "Elementary Processes of Organic Photovoltaics" [SPP 1355]; Helmholtz Energy Alliance for Hybrid Photovoltaics; BMBF (PVcomB)
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Physik und Astronomie
Peer Review:Referiert