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Ultrafast Hole‐Transfer Dynamics in Polymer/PCBM Bulk Heterojunctions
Author(s) -
Bakulin Artem A.,
Hummelen Jan C.,
Pshenichnikov Maxim S.,
van Loosdrecht Paul H. M.
Publication year - 2010
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200902099
Subject(s) - materials science , exciton , ultrashort pulse , polymer , polymer blend , heterojunction , excitation , chemical physics , fullerene , phase (matter) , relaxation (psychology) , nanoclusters , optoelectronics , chemical engineering , nanotechnology , optics , composite material , organic chemistry , condensed matter physics , psychology , social psychology , laser , chemistry , physics , electrical engineering , engineering , copolymer
Ultrafast dynamics of the hole‐transfer process from methanofullerene to a polymer in a polymer/PCBM bulk heterojunction are directly resolved. Injection of holes into MDMO‐PPV is markedly delayed with respect to [60]PCBM excitation. The fastest component of the delayed response is attributed to the PCBM–polymer hole‐transfer process (30 ± 10 fs), while the slower component (∼150 fs) is provisionally assigned to energy transfer and/or relaxation inside PCBM nanoclusters. The charge generation through the hole transfer is therefore as fast and efficient as through the electron‐transfer process. Exciton harvesting efficiency after PCBM excitation crucially depends on the concentration of the methanofullerene in the blend, which is related to changes in the blend morphology. Ultrafast charge generation is most efficient when the characteristic scale of phase separation in the blend does not exceed ∼20 nm. At larger‐scale phase separation, the exciton harvesting dramatically declines. The obtained results on the time scales of the ultrafast charge generation after PCBM excitation and their dependence on blend composition and morphology are instrumental for the future design of fullerene‐derivative‐based photovoltaic devices.