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Ultrafast charge carrier dynamics in CH₃NH₃PbI₃: evidence for hot hole injection into spiro-OMeTAD

  • Brauer, Jan C. Department of Chemistry, University of Fribourg, Switzerland
  • Lee, Yong Hui Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, Switzerland
  • Nazeeruddin, Mohammad Khaja Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, Switzerland
  • Banerji, Natalie Department of Chemistry, University of Fribourg, Switzerland
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    23.06.2016
Published in:
  • Journal of Materials Chemistry C. - 2016, vol. 4, no. 25, p. 5922–5931
English Hybrid organic–inorganic metal perovskites have emerged as highly promising materials for solar energy conversion. However, key questions regarding the working principles of perovskite solar cells remain to be answered in order to improve the design of such devices. In the present study, we have investigated the influence of excess excitation energy on the initial photo-products generated from FTO/meso- TiO2/CH3NH3PbI3 samples. We find that upon resonant excitation at the band edge, part of the formation of free charges passes via an excitonic state that dissociates on the sub-picosecond time scale. An exciton binding energy of <10 meV is estimated from the lifetime of the exciton. On the other hand, if excess energy is available, free charges are directly generated. We have then investigated the hole injection into spiro- OMeTAD at the CH3NH3PbI3/spiro-OMeTAD interface. By following spectroscopically the generation of the oxidized form of the molecular hole conductor spiro-OMeTAD, we confirm that the hole injection is essentially ultrafast and occurs on the sub-80 femtosecond time scale. On this time scale, the hole injection competes with carrier cooling after photo-excitation and therefore the charge injection can occur from non- thermalised states.
Faculty
Faculté des sciences et de médecine
Department
Département de Chimie
Language
  • English
Classification
Chemistry
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https://folia.unifr.ch/unifr/documents/304978
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