TY - JOUR
T1 - Exciton Binding Energy and the Nature of Emissive States in Organometal Halide Perovskites
AU - Zheng, Kaibo
AU - Zhu, Qiushi
AU - Abdellah, Mohamed
AU - Messing, Maria E.
AU - Zhang, Wei
AU - Generalov, Alexander
AU - Niu, Yuran
AU - Ribaud, Lynn
AU - Canton, Sophie E.
AU - Pullerits, Tõnu
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/8/6
Y1 - 2015/8/6
N2 - Characteristics of nanoscale materials are often different from the corresponding bulk properties providing new, sometimes unexpected, opportunities for applications. Here we investigate the properties of 8 nm colloidal nanoparticles of MAPbBr3 perovskites and contrast them to the ones of large microcrystallites representing a bulk. X-ray spectroscopies provide an exciton binding energy of 0.32 ± 0.10 eV in the nanoparticles. This is 5 times higher than the value of bulk crystals (0.084 ± 0.010 eV), and readily explains the high fluorescence quantum yield in nanoparticles. In the bulk, at high excitation concentrations, the fluorescence intensity has quadratic behavior following the Saha-Langmuir model due to the nongeminate recombination of charges forming the emissive exciton states. In the nanoparticles, a linear dependence is observed since the excitation concentration per particle is significantly less than one. Even the bulk shows linear emission intensity dependence at lower excitation concentrations. In this case, the average excitation spacing becomes larger than the carrier diffusion length suppressing the nongeminate recombination. From these considerations we obtain the charge carrier diffusion length in MAPbBr3 of 100 nm.
AB - Characteristics of nanoscale materials are often different from the corresponding bulk properties providing new, sometimes unexpected, opportunities for applications. Here we investigate the properties of 8 nm colloidal nanoparticles of MAPbBr3 perovskites and contrast them to the ones of large microcrystallites representing a bulk. X-ray spectroscopies provide an exciton binding energy of 0.32 ± 0.10 eV in the nanoparticles. This is 5 times higher than the value of bulk crystals (0.084 ± 0.010 eV), and readily explains the high fluorescence quantum yield in nanoparticles. In the bulk, at high excitation concentrations, the fluorescence intensity has quadratic behavior following the Saha-Langmuir model due to the nongeminate recombination of charges forming the emissive exciton states. In the nanoparticles, a linear dependence is observed since the excitation concentration per particle is significantly less than one. Even the bulk shows linear emission intensity dependence at lower excitation concentrations. In this case, the average excitation spacing becomes larger than the carrier diffusion length suppressing the nongeminate recombination. From these considerations we obtain the charge carrier diffusion length in MAPbBr3 of 100 nm.
KW - exciton binding energy
KW - fluorescence
KW - nanoparticles
KW - perovskites
KW - photoelectron spectroscopy
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U2 - 10.1021/acs.jpclett.5b01252
DO - 10.1021/acs.jpclett.5b01252
M3 - Article
C2 - 26267190
AN - SCOPUS:84938693001
SN - 1948-7185
VL - 6
SP - 2969
EP - 2975
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 15
ER -