TY - JOUR
T1 - Direct probing of gap states and their passivation in halide perovskites by high-sensitivity, variable energy ultraviolet photoelectron spectroscopy
AU - Levine, Igal
AU - Ishii, Hisao
AU - Shimizu, Kohei
AU - Lomuscio, Alberto
AU - Kulbak, Michael
AU - Rehermann, Carolin
AU - Zohar, Arava
AU - Abdi-Jalebi, Mojtaba
AU - Zhao, Baodan
AU - Siebentritt, Susanne
AU - Zu, Fengshuo
AU - Koch, Norbert
AU - Kahn, Antoine
AU - Hodes, Gary
AU - Friend, Richard H.
AU - Cahen, David
N1 - Publisher Copyright:
© 2021 American Chemical Society. All rights reserved.
PY - 2021/3/11
Y1 - 2021/3/11
N2 - Direct detection of intrinsic defects in halide perovskites (HaPs) by standard methods utilizing optical excitation is quite challenging, due to the low density of defects in most samples of this family of materials (≤1015 cm-3 in polycrystalline thin films and ≤1011 cm-3 in single crystals, except melt-grown ones). While several electrical methods can detect defect densities <1015 cm-3, such as deep level transient spectroscopy (DLTS) or thermally stimulated current (TSC), they require preparation of ohmic and/or rectifying electrical contacts to the sample, which not only poses a challenge by itself in the case of HaPs but also may create defects at the contact-HaP interface and introduce extrinsic defects into the HaP. Here, we show that low-energy photoelectron spectroscopy measurements can be used to obtain directly the energy position of gap states in Br-based wide-bandgap (Eg > 2 eV) HaPs. By measuring HaP layers on both hole- and electron-contact layers, as well as single crystals without contacts, we conclude that the observed deep defects are intrinsic to the Br-based HaP, and we propose a passivation route via the incorporation of a 2Dforming ligand into the precursor solution.
AB - Direct detection of intrinsic defects in halide perovskites (HaPs) by standard methods utilizing optical excitation is quite challenging, due to the low density of defects in most samples of this family of materials (≤1015 cm-3 in polycrystalline thin films and ≤1011 cm-3 in single crystals, except melt-grown ones). While several electrical methods can detect defect densities <1015 cm-3, such as deep level transient spectroscopy (DLTS) or thermally stimulated current (TSC), they require preparation of ohmic and/or rectifying electrical contacts to the sample, which not only poses a challenge by itself in the case of HaPs but also may create defects at the contact-HaP interface and introduce extrinsic defects into the HaP. Here, we show that low-energy photoelectron spectroscopy measurements can be used to obtain directly the energy position of gap states in Br-based wide-bandgap (Eg > 2 eV) HaPs. By measuring HaP layers on both hole- and electron-contact layers, as well as single crystals without contacts, we conclude that the observed deep defects are intrinsic to the Br-based HaP, and we propose a passivation route via the incorporation of a 2Dforming ligand into the precursor solution.
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U2 - 10.1021/acs.jpcc.0c11627
DO - 10.1021/acs.jpcc.0c11627
M3 - Article
AN - SCOPUS:85103426099
SN - 1932-7447
VL - 125
SP - 5217
EP - 5225
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 9
ER -