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  Prajongtat, P.; Wargulski, D.R.; Unold, T.; Dittrich, T.: Photochemically Driven Modulated Charge Transfer at Local Contacts between CH₃NH₃PbI₃ and Carboxylated Multiwalled Carbon Nanotubes. The Journal of Physical Chemistry C 120 (2016), p. 3876-3881

10.1021/acs.jpcc.5b11854

Abstract:
Spectral dependent charge separation was investigated by modulated surface photovoltage (SPV) on layer systems with local contacts between CH3NH3PbI3 and PEDOT:PSS mixed with carboxylated multiwalled carbon nanotubes (MWCNT-COOH). In-phase SPV signals changed the sign with increasing amount of MWCNT-COOH in the PEDOT:PSS whereas the spectra could be approximated by a superposition of the spectra obtained for pure PEDOT:PSS and for PEDOT:PSS with 1.6 wt % of MWCNT-COOH. This was not the case for the control sample with pristine MWCNT. For a complex of a single-walled CNT-COOH (SWCNT-COOH) with a perovskite particle, density functional theory calculations showed an electron transfer to the perovskite which was not the case for a pristine SWCNT. Therefore, the transfer of electrons from MWCNT-COOH into illuminated CH3NH3PbI3 dominates fast separation of photogenerated charge carriers at local contacts with MWCNT-COOH.