TY - JOUR
T1 - Quantifying Polaron Formation and Charge Carrier Cooling in Lead-Iodide Perovskites
AU - Bretschneider, Simon A.
AU - Ivanov, Ivan
AU - Wang, Hai I.
AU - Miyata, Kiyoshi
AU - Zhu, Xiaoyang
AU - Bonn, Mischa
N1 - Funding Information:
S.A.B. and I.I. contributed equally to this work. The authors are grateful to Daniel Niesner for discussions and critical reading of a draft of this manuscript. The authors also acknowledge fruitful discussions with Stefan Weber, Jarvist Frost, Hassan Hafez, Heejae Kim, Maksim Grechko, Miguel Antonio Donovan, Enrique Canovas, Ilka Hermes, Keno Krewer, Eduard Unger, Alexander Tries, and Marco Ballabio; Michael Steiert for XRD measurements; Gunnar Glaser for SEM measurements; Simon Schlegel for providing the TiO2 sample; and Amelie Axt for help with the TOC figure. S.A.B. acknowledges funding from the Max Planck Graduate Center. K.M. acknowledges the Japan Society for the Promotion of Science (JSPS) for financial support. X.Y.Z. acknowledges support by the Vannevar Bush Faculty Fellowship by DOD, Grant # N00014-18-1-2080.
Publisher Copyright:
© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2018/7/19
Y1 - 2018/7/19
N2 - Notwithstanding the success of lead-halide perovskites in emerging solar energy conversion technologies, many of the fundamental photophysical phenomena in this material remain debated. Here, the initial steps following photogeneration of free charge carriers in lead-iodide perovskites are studied, and timescales of charge carrier cooling and polaron formation, as a function of temperature and charge carrier excess energy, are quantified. It is found, using terahertz time-domain spectroscopy (THz-TDS), that the observed femtosecond rise in the photoconductivity can be described very well using a simple model of sequential charge carrier cooling and polaron formation. For excitation above the bandgap, the carrier cooling time depends on the charge carrier excess energy and lattice temperature, with cooling rates varying between 1 and 6 meV fs−1, depending on the cation. While carrier cooling depends on the cation, polaron formation occurs within ≈400 fs in CH3NH3PbI3 (MAPbI3), CH(NH2)2PbI3 (FAPbI3), and CsPbI3. Its formation time is independent of temperature between 160 and 295 K. The very similar polaron formation dynamics observed for the three perovskites points to the critical role of the inorganic lattice, rather than the cations, for polaron formation.
AB - Notwithstanding the success of lead-halide perovskites in emerging solar energy conversion technologies, many of the fundamental photophysical phenomena in this material remain debated. Here, the initial steps following photogeneration of free charge carriers in lead-iodide perovskites are studied, and timescales of charge carrier cooling and polaron formation, as a function of temperature and charge carrier excess energy, are quantified. It is found, using terahertz time-domain spectroscopy (THz-TDS), that the observed femtosecond rise in the photoconductivity can be described very well using a simple model of sequential charge carrier cooling and polaron formation. For excitation above the bandgap, the carrier cooling time depends on the charge carrier excess energy and lattice temperature, with cooling rates varying between 1 and 6 meV fs−1, depending on the cation. While carrier cooling depends on the cation, polaron formation occurs within ≈400 fs in CH3NH3PbI3 (MAPbI3), CH(NH2)2PbI3 (FAPbI3), and CsPbI3. Its formation time is independent of temperature between 160 and 295 K. The very similar polaron formation dynamics observed for the three perovskites points to the critical role of the inorganic lattice, rather than the cations, for polaron formation.
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U2 - 10.1002/adma.201707312
DO - 10.1002/adma.201707312
M3 - Article
AN - SCOPUS:85047781521
SN - 0935-9648
VL - 30
JO - Advanced Materials
JF - Advanced Materials
IS - 29
M1 - 1707312
ER -