Double Charged Surface Layers in Lead Halide Perovskite Crystals.
Understanding defect chemistry, particularly ion migration, and its significant effect on the surface's optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.
Smritakshi P
SP
Sarmah
Mathematical Institute, University of Oxford , Woodstock Road, Oxford OX2 6GG, United Kingdom.
Victor M
VM
Burlakov
Emre
0000-0001-7208-4803
E
Yengel
Banavoth
0000-0002-7806-2274
B
Murali
Erkki
E
Alarousu
Ahmed M
AM
El-Zohry
Chen
C
Yang
Mohd S
0000-0003-1369-1421
MS
Alias
Ayan A
AA
Zhumekenov
Makhsud I
MI
Saidaminov
Namchul
N
Cho
Nimer
N
Wehbe
Somak
S
Mitra
Idris
I
Ajia
Sukumar
S
Dey
Ahmed E
0000-0002-3411-6808
AE
Mansour
Maged
M
Abdelsamie
Aram
A
Amassian
Iman S
IS
Roqan
Boon S
BS
Ooi
Mathematical Institute, University of Oxford , Woodstock Road, Oxford OX2 6GG, United Kingdom.
Alain
A
Goriely
Osman M
0000-0002-3428-1002
OM
Bakr
Omar F
0000-0001-8500-1130
OF
Mohammed
Nanometer surface layers; defects; ion migration; lead halide perovskite crystal; one vs two-photon excitation