Issue 25, 2016

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

Abstract

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.

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

Supplementary files

Article information

Article type
Paper
Submitted
22 fev 2016
Accepted
15 may 2016
First published
16 may 2016

J. Mater. Chem. C, 2016,4, 5922-5931

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

J. C. Brauer, Y. H. Lee, M. K. Nazeeruddin and N. Banerji, J. Mater. Chem. C, 2016, 4, 5922 DOI: 10.1039/C6TC00763E

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