## Role of charge separation mechanism and local disorder at hybrid solar cell interfaces

2015
##### Authors
Paquin, Francis
Dion-Bertrand, Laura-Isabelle
Paré-Labrosse, Olivier
Silva, Carlos
Journal article
##### Published in
Physical Review B ; 91 (2015), 3. - 035304. - ISSN 1098-0121. - eISSN 1095-3795
##### Abstract
Dye-sensitized metal oxide polymer hybrid solar cells deliver a promising basis in organic solar cell development due to many conceptual advantages. Since the power conversion efficiency is still in a noncompetitive state, it has to be understood how the photocurrent contribution can be maximized (i.e., which dye-polymer properties are most beneficial for efficient charge generation in hybrid solar cells). By the comparison of three model systems for hybrid solar cells with TiO2-dye-polymer interfaces, this paper was aimed at elucidating the role of the exact mechanism of charge generation. In the exciton dissociation (ED) case, an exciton that is generated in the polymer is split at the dye-polymer interface. Alternatively, this exciton can be transferred to the dye via an energy transfer (ET), upon which charge separation occurs between dye and TiO2. For comparison, the third case is included in which the high lowest unoccupied molecular orbital of the dye does not allow exciton separation or ET from the dye to the polymer, so that the dye only is responsible for charge generation. To separate effects owing to differences in energy levels of the involved materials from the impact of local order and disorder in the polymer close to the interface, this paper further comprises a detailed analysis of the polymer crystallinity based on the H-aggregate model. While the massive impact of the poly(3-hexylthiophene) crystallinity on device function has been outlined for bare metal oxide-polymer interfaces, it has not been considered for hybrid solar cells with dye-sensitized TiO2. The results presented here indicate that all dye molecules in general influence the polymer morphology, which has to be taken into account for future optimization of hybrid solar cells. Apart from that, it can be suggested that ED on the polymer needs an additional driving force to work efficiently; thus, energy transfer seems to be currently the most promising strategy to increase the polymer photocurrent contribution.
530 Physics
##### Cite This
ISO 690EHRENREICH, Philipp, Thomas PFADLER, Francis PAQUIN, Laura-Isabelle DION-BERTRAND, Olivier PARÉ-LABROSSE, Carlos SILVA, Jonas WEICKERT, Lukas SCHMIDT-MENDE, 2015. Role of charge separation mechanism and local disorder at hybrid solar cell interfaces. In: Physical Review B. 91(3), 035304. ISSN 1098-0121. eISSN 1095-3795. Available under: doi: 10.1103/PhysRevB.91.035304
BibTex
@article{Ehrenreich2015charg-30386,
year={2015},
doi={10.1103/PhysRevB.91.035304},
title={Role of charge separation mechanism and local disorder at hybrid solar cell interfaces},
number={3},
volume={91},
issn={1098-0121},
journal={Physical Review B},
author={Ehrenreich, Philipp and Pfadler, Thomas and Paquin, Francis and Dion-Bertrand, Laura-Isabelle and Paré-Labrosse, Olivier and Silva, Carlos and Weickert, Jonas and Schmidt-Mende, Lukas},
note={Article Number: 035304}
}

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<dcterms:abstract xml:lang="eng">Dye-sensitized metal oxide polymer hybrid solar cells deliver a promising basis in organic solar cell development due to many conceptual advantages. Since the power conversion efficiency is still in a noncompetitive state, it has to be understood how the photocurrent contribution can be maximized (i.e., which dye-polymer properties are most beneficial for efficient charge generation in hybrid solar cells). By the comparison of three model systems for hybrid solar cells with TiO2-dye-polymer interfaces, this paper was aimed at elucidating the role of the exact mechanism of charge generation. In the exciton dissociation (ED) case, an exciton that is generated in the polymer is split at the dye-polymer interface. Alternatively, this exciton can be transferred to the dye via an energy transfer (ET), upon which charge separation occurs between dye and TiO2. For comparison, the third case is included in which the high lowest unoccupied molecular orbital of the dye does not allow exciton separation or ET from the dye to the polymer, so that the dye only is responsible for charge generation. To separate effects owing to differences in energy levels of the involved materials from the impact of local order and disorder in the polymer close to the interface, this paper further comprises a detailed analysis of the polymer crystallinity based on the H-aggregate model. While the massive impact of the poly(3-hexylthiophene) crystallinity on device function has been outlined for bare metal oxide-polymer interfaces, it has not been considered for hybrid solar cells with dye-sensitized TiO2. The results presented here indicate that all dye molecules in general influence the polymer morphology, which has to be taken into account for future optimization of hybrid solar cells. Apart from that, it can be suggested that ED on the polymer needs an additional driving force to work efficiently; thus, energy transfer seems to be currently the most promising strategy to increase the polymer photocurrent contribution.</dcterms:abstract>
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