Perovskites attract attention as efficient light absorbers for solar cells due to their high-power conversion efficiency (up to 24%). The high photoelectric conversion efficiency is greatly affected by a suitable band structure. Cation substitution can be an effective approach to tune the electronic band structure of lead halide perovskites. In this work, superalkali cations were introduced to replace the Cs+ cation in the CsPbBr3 material. The bimetallic superalkalis (LiMg, NaMg, LiCa, and NaCa) were inserted since they are structurally simple systems and have a strong tendency to lose one electron to achieve a closed-shell cation. The cation substitution in the lead halide perovskite leads to changes in the shape of both valence and conduction bands compared to CsPbBr3. Introducing superalkali cations produces extra electronic states close to the Fermi level, which arise from the formation of alkali earth metal states at the top of the valence band. Our first-principles computations reveal that bimetallic superalkali substitution decreases the bandgap of the perovskite. The bandgaps of MgLi–PbBr3 (1.35 eV) and MgNa–PbBr3 (1.06 eV) are lower than the bandgap of CsPbBr3 (2.48 eV) and within the optimal bandgap (i.e., 1.1–1.4 eV) for single-junction solar cells. Thus, the MgLi–PbBr3 and MgNa–PbBr3 inorganic perovskites are promising candidates for high-efficiency solar cells.

1.
T. C.
Sum
,
M.
Righetto
, and
S. S.
Lim
, “
Quo vadis, perovskite emitters?
,”
J. Chem. Phys.
152
,
130901
(
2020
).
2.
R. X.
Yang
and
L. Z.
Tan
, “
Understanding size dependence of phase stability and band gap in CsPbI3 perovskite nanocrystals
,”
J. Chem. Phys.
152
,
034702
(
2020
).
3.
H.
Fang
and
P.
Jena
, “
Super-ion inspired colorful hybrid perovskite solar cells
,”
J. Mater. Chem. A
4
,
4728
4737
(
2016
).
4.
S.
Giri
,
S.
Behera
, and
P.
Jena
, “
Superalkalis and superhalogens as building blocks of supersalts
,”
J. Phys. Chem. A
118
,
638
645
(
2014
).
5.
W. M.
Sun
and
D.
Wu
, “
Recent progress on the design, characterization, and application of superalkalis
,”
Chem.-Eur. J.
25
,
9568
9579
(
2019
).
6.
I.
Swierszcz
and
I.
Anusiewicz
, “
Low ionization potentials of Na4OCN superalkali molecules
,”
Mol. Phys.
109
,
1739
1748
(
2011
).
7.
I.
Anusiewicz
, “
Superalkali molecules containing halogenoids
,”
J. Theor. Comput. Chem.
10
,
191
208
(
2011
).
8.
C.
Sikorska
and
N.
Gaston
, “
N4Mg6M (M = Li, Na, K) superalkalis for CO2 activation
,”
J. Chem. Phys.
153
,
144301
(
2020
).
9.
B. G. A.
Brito
,
G.-Q.
Hai
, and
L.
Cândido
, “
Interpretation of the photoelectron spectra of superalkali species: Li3O and Li3O
,”
J. Chem. Phys.
151
,
014303
(
2019
).
10.
M.
Gutowski
and
J.
Simons
, “
Anionic states of LiFLi
,”
J. Chem. Phys.
100
,
1308
1311
(
1994
).
11.
C.
Paduani
and
A. M.
Rappe
, “
Tuning the gap of lead-based halide perovskites by introducing superalkali species at the cationic sites of ABX3-type structure
,”
Phys. Chem. Chem. Phys.
19
,
20619
20626
(
2017
).
12.
G. E.
Eperon
,
G. M.
Paternò
,
R. J.
Sutton
,
A.
Zampetti
,
A. A.
Haghighirad
,
F.
Cacialli
, and
H. J.
Snaith
, “
Inorganic caesium lead iodide perovskite solar cells
,”
J. Mater. Chem. A
3
,
19688
19695
(
2015
).
13.
W.
Shockley
and
H. J.
Queisser
, “
Detailed balance limit of efficiency of p-n junction solar cells
,”
J. Appl. Phys.
32
,
510
519
(
1961
).
14.
W. M.
Sun
,
X. L.
Zhang
,
K. Y.
Pan
,
J. H.
Chen
,
D.
Wu
,
C. Y.
Li
,
Y.
Li
, and
Z. R.
Li
, “
On the possibility of using the jellium model as a guide to design bimetallic superalkali cations
,”
Chem.-Eur. J.
25
,
4358
4366
(
2019
).
15.
G.
Kresse
and
J.
Hafner
, “
Ab initio molecular dynamics for liquid metals
,”
Phys. Rev. B
47
,
558
561
(
1993
).
16.
G.
Kresse
and
J.
Hafner
, “
Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium
,”
Phys. Rev. B
49
,
14251
14269
(
1994
).
17.
G.
Kresse
and
J.
Furthmüller
, “
Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
,”
Comput. Mater. Sci.
6
,
15
50
(
1996
).
18.
J.
Furthmüller
,
J.
Hafner
, and
G.
Kresse
, “
Dimer reconstruction and electronic surface states on clean and hydrogenated diamond (100) surfaces
,”
Phys. Rev. B
53
,
7334
7351
(
1996
).
19.
J. P.
Perdew
,
K.
Burke
, and
M.
Ernzerhof
, “
Generalized gradient approximation made simple
,”
Phys. Rev. Lett.
77
,
3865
3868
(
1996
).
20.
J.
Paier
,
R.
Hirschl
,
M.
Marsman
, and
G.
Kresse
, “
The Perdew-Burke-Ernzerhof exchange-correlation functional applied to the G2-1 test set using a plane-wave basis set
,”
J. Chem. Phys.
122
,
234102
(
2005
).
21.
L. N.
Anderson
,
F. W.
Aquino
,
A. E.
Raeber
,
X.
Chen
, and
B. M.
Wong
, “
Halogen bonding interactions: Revised benchmarks and a new assessment of exchange vs dispersion
,”
J. Chem. Theory Comput.
14
,
180
190
(
2018
).
22.
Q.
Yang
,
M.
Wu
, and
X. C.
Zeng
, “
Constructing stable and potentially high-performance hybrid organic-inorganic perovskites with ‘unstable’ cations
,”
Research
2020
,
1986576
.
23.
R.
Kevorkyants
,
N. I.
Selivanov
, and
A. V.
Emeline
, “
Modulating electronic properties of pyridinium lead halide perovskites via fluorinated methyl substituents
,”
Mater. Chem. Phys.
273
,
125139
(
2021
).
24.
A. M.
Ganose
,
A. J.
Jackson
, and
D. O.
Scanlon
, “
sumo: Command-line tools for plotting and analysis of periodic ab initio calculations
,”
J. Open Source Software
3
,
717
(
2018
).
25.
V. M.
Goldschmidt
, “
The laws of crystal chemistry
,”
Naturwissenschaften
14
,
477
485
(
1926
).
26.
G.
Kieslich
,
S. J.
Sun
, and
A. K.
Cheetham
, “
Solid-state principles applied to organic-inorganic perovskites: New tricks for an old dog
,”
Chem. Sci.
5
,
4712
4715
(
2014
).
27.
C. H.
Li
,
X. G.
Lu
,
W. Z.
Ding
,
L. M.
Feng
,
Y. H.
Gao
, and
Z. G.
Guo
, “
Formability of ABX3 (X = F, Cl, Br, I) halide perovskites
,”
Acta Crystallogr., Sect. B: Struct. Sci.
64
,
702
707
(
2008
).
28.
H. M.
Ghaithan
,
S. M. H.
Qaid
,
Z. A.
Alahmed
,
M.
Hezam
,
A.
Lyras
,
M.
Amer
, and
A. S.
Aldwayyan
, “
Anion substitution effects on the structural, electronic, and optical properties of inorganic CsPb(I1–xBrx)3 and CsPb(Br1–xClx)3 perovskites: Theoretical and experimental approaches
,”
J. Phys. Chem. C
125
,
886
897
(
2021
).
29.
M.
Ong
,
D. M.
Guzman
,
Q.
Campbell
,
I.
Dabo
, and
R. A.
Jishi
, “
BaZrSe3: Ab initio study of anion substitution for bandgap tuning in a chalcogenide material
,”
J. Appl. Phys.
125
,
235702
(
2019
).
30.
Z.-Y.
Wang
,
Y.
Chen
,
C.
Zhang
,
D.
Wang
,
P.
Liang
,
H.
Zhang
,
R.-J.
Xie
, and
L.
Wang
, “
Electronic structure and optical properties of vacancy-ordered double perovskites Cs2Pd BrxCl6–x by first-principles calculation
,”
J. Phys. Chem. C
124
,
13310
13315
(
2020
).
31.
G.
Tang
,
P.
Ghosez
, and
J. W.
Hong
, “
Band-edge orbital engineering of perovskite semiconductors for optoelectronic applications
,”
J. Phys. Chem. Lett.
12
,
4227
4239
(
2021
).
32.
T.
Zhou
,
Y.
Zhang
,
M.
Wang
,
Z.
Zang
, and
X.
Tang
, “
Tunable electronic structures and high efficiency obtained by introducing superalkali and superhalogen into AMX3-type perovskites
,”
J. Power Sources
429
,
120
126
(
2019
).
33.
Encyclopedia of Physical Science and Technology
, edited by
R. A.
Meyers
(
Ramtech, Inc.
,
Tarzana, CA
,
2001
).
34.
P. J.
Foster
,
R. E.
Leckenby
, and
E. J.
Robbins
, “
The ionization potentials of clustered alkali metal atoms
,”
J. Phys. B: At. Mol. Phys.
2
,
478
483
(
1969
).

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