TY - JOUR
T1 - Spatially segregated free-carrier and exciton populations in individual lead halide perovskite grains
AU - Nah, S.
AU - Spokoyny, B.
AU - Stoumpos, C.
AU - Soe, C. M.M.
AU - Kanatzidis, Mercouri G
AU - Harel, E.
PY - 2017/5/1
Y1 - 2017/5/1
N2 - The nature of charge carriers in methylammonium lead iodide perovskites (MAPbI 3) at room temperature is still a matter of considerable debate. Here, we demonstrate that within single grains of MAPbI 3, strong spatial heterogeneities on the nanometre length scale are present and associated with simultaneous free-carrier and exciton populations. These heterogeneous populations, hidden in ensemble measurements, have a signature of spatially resolved relaxation dynamics for above-bandgap photoexcitation. Using spectrally resolved transient absorption microscopy, we directly observe both red- and blueshifts of the band-edge absorption across individual grains due to a dynamic Stark shift and screening of excitonic transitions by hot carriers. These observations help address a long-standing debate on the identity of the charge carriers, showing that both excitons and free carriers coexist, but are spatially segregated on the length scale of hundreds of nanometres.
AB - The nature of charge carriers in methylammonium lead iodide perovskites (MAPbI 3) at room temperature is still a matter of considerable debate. Here, we demonstrate that within single grains of MAPbI 3, strong spatial heterogeneities on the nanometre length scale are present and associated with simultaneous free-carrier and exciton populations. These heterogeneous populations, hidden in ensemble measurements, have a signature of spatially resolved relaxation dynamics for above-bandgap photoexcitation. Using spectrally resolved transient absorption microscopy, we directly observe both red- and blueshifts of the band-edge absorption across individual grains due to a dynamic Stark shift and screening of excitonic transitions by hot carriers. These observations help address a long-standing debate on the identity of the charge carriers, showing that both excitons and free carriers coexist, but are spatially segregated on the length scale of hundreds of nanometres.
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U2 - 10.1038/nphoton.2017.36
DO - 10.1038/nphoton.2017.36
M3 - Article
AN - SCOPUS:85016123099
VL - 11
SP - 285
EP - 289
JO - Nature Photonics
JF - Nature Photonics
SN - 1749-4885
IS - 5
ER -