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, M.
AU - Harel, E.
N1 - Funding Information:
E.H. acknowledges support, in part, from the Air Force Office of Scientific Research (FA9550-14-1-0005) and the Packard Foundation (2013-39272). M.K. acknowledges support from the US Department of Energy, Office of Science, Basic Energy Sciences (DE-SC-0012541). The electron microscopy work made use of the EPIC facility of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC programme (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation and the State of Illinois (through the IIN). S.N. acknowledges support from the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry.
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.
UR - http://www.scopus.com/inward/record.url?scp=85016123099&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85016123099&partnerID=8YFLogxK
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 -