INORGANIC CHEMISTRYFRONTIERSRESEARCH ARTICLE

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Adhesion, stability, structural and electronic
properties of perovskite/BaWO4 heterostructures:ﬁrst-principles and experimental
characterizations†
Yao Guo, a Shiding Zhang,*a,b Zhaoyu Zhang,a Yuanbin Xue,a Jianxin Li,a
Haixiang Song,a Yuhua Wang *b and Qing Shen *c
The poor stability of lead halide perovskites poses a critical challenge for realizing potential applications.
Constructing latticed-matched perovskite/BaWO4 heterostructures is highly advantageous for achieving
enhanced stability. However, there is limited knowledge about the interfacial properties. Herein, we conducted combined ﬁrst-principles and experimental investigations of the perovskite/BaWO4 heterostructures in this work. First, eight diﬀerent interfacial conﬁgurations were constructed and investigatedsystematically. The inﬂuence of surface terminations on interfacial properties was examined through theadhesive strength and electronic structures. The results of adhesion work suggest that the MAPbBr3/
BaWO4 conﬁgurations possess stronger interfacial interaction than the CsPbBr3/BaWO4 conﬁgurations.
The formation of BaW/PbBr and BaW/MAPb conﬁgurations was more facile compared to their counterparts. The interfacial charge transfer direction, potential diﬀerence, and valence band edges of the perovskite/BaWO4 heterostructures were found to be signiﬁcantly inﬂuenced by the surface termination of

Received 24th January 2024,
Accepted 18th March 2024
DOI: 10.1039/d4qi00231hrsc.li/frontiers-inorganic

1.

BaWO4. The absorption intensity of the perovskite/BaWO4 heterostructures is signiﬁcantly aﬀected by thesurface termination of the perovskite. Finally, the CsPbBr3/BaWO4 heterostructure was fabricated andcharacterized, thereby validating the ﬁrst-principles predictions. This study provides a fundamental contribution to establishing perovskite/BaWO4 heterostructures for the advancement of perovskite-based
optoelectronic devices.

Introduction

During the past decade, lead bromide perovskites in the guiseof colloidal nanocrystals (NCs), such as cesium lead bromide(CsPbBr3) and methylammonium lead bromide (MAPbBr3),
have been extensively explored for diverse applications, suchas light-emitting diodes (LEDs) and photodetectors, owing totheir distinctive photophysical characteristics including
tunable band gap, high absorption coeﬃcient, strong defecttolerance, high quantum yield, low fabrication cost, and soon.1–5 Unfortunately, the excellent properties and exciting pro-aSchool of Materials Science and Engineering, Anyang Institute of Technology,
Anyang, 455000, China. E-mail: zsd@ayit.edu.cnbHubei Province Key Laboratory of System Science in Metallurgical Process, Wuhan
University of Science and Technology, Wuhan, 430081, China.
E-mail: wangyuhua@wust.edu.cn
cFaculty of Informatics and Engineering, The University of Electro-Communications,Tokyo, 182-8585, Japan. E-mail: shen@pc.uec.ac.jp† Electronic supplementary information (ESI) available. See DOI: https://doi.org/
10.1039/d4qi00231hThis journal is © the Partner Organisations 2024

gress of lead bromide perovskite NCs are overshadowed bytheir limited operational lifetime under ambient conditions,which is severely hindering their real-world implementation
and widespread adoption. The instability of perovskite NCs
renders them vulnerable to environmental factors, which
results in a series of detrimental eﬀects, including structural
alterations and phase transitions, reduced luminescenceeﬃciency, and limited electron mobility.6–10 An eﬃcient way toenhance the stability of perovskite NCs and preserve their colloidal stability and photoluminescence is to couple them withanother material to form a heterostructure.11–16 Although perovskite NC heterostructures have been successfully designed toenhance their optical stability and emission intensity, theirapplications are still limited to a few combinations.17–22 The
design of perovskite NC heterostructures in combination withlattice-matched materials is still a topic that requires further
investigation.
Barium tungstate (BaWO4) with a scheelite structure is
known for its high ionic/electronic conductivity and highthermal/chemical stability, and has potential applications in
catalysis.23–26 Recently, the heterostructural growth of CsPbBr3

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Research Article
and MAPbBr3 NCs on a BaWO4 crystal was successfully demonstrated based on lattice matching.27,28 Compared to the pure
perovskite, the perovskite/BaWO4 heterostructures exhibitedenhanced luminescence intensity and sustained stability
against UV-light radiation, heat, and diverse solvents. The
BaWO4 crystal can eﬀectively inhibit halogen migration in theperovskite, leading to tunable emissions with diﬀerent compositions. This implies the great potential of combining barium
tungstate with lead bromide perovskite in advanced anticounterfeiting and encryption applications. To date, the CsPbBr3/
BaWO4 and MAPbBr3/BaWO4 heterostructures have been
examined by experimental investigations.27,28 The interfacialcharacteristics of these heterostructures, which are directly
determined by the arrangement of atoms and their interactions, are still not fully understood. Systematic and comparative investigations of the interfacial systems are therefore ofgreat interest.29–33 In this study, we utilize the first-principles
approach to explore the heterostructures of CsPbBr3/BaWO4
and MAPbBr3/BaWO4. Moreover, the composition and morphological characteristics were further verified by microscopic
and spectroscopic tools. The interfacial behavior and mechanism of the heterostructure were investigated by combining
theoretical and experimental approaches to assess the photocatalytic potential of these newly developed heterostructures.

2. Computational and experimental
details
The first-principles density functional theory (DFT) calculations were carried out based on projector augmented wave
(PAW) formalism34 within the Vienna ab initio simulation
package (VASP, version 5.4.4).35–37 The exchange correlationeﬀect was evaluated by means of the generalized gradientapproximation (GGA) of the Perdew–Burke–Ernzerhof (PBE)
functional.38 The kinetic plane wave energy cutoﬀ was set to450 eV with Gaussian smearing (σ = 0.1 eV).39 Brillouin-zone
integration was done using the Monkhorst–Pack40 k-pointmesh with 0.02 Å−1 separation. The vacuum layer thickness
was set to 15 Å to neglect the coupling between the images.
The spurious interactions between periodic images were significantly reduced by using the dipole correction in the VASP
(IDIPOL = 3). The DFT-D3 with the BJ-damping method41 wasincluded to consider the van der Waals (vdW) interactions.
The convergence criteria for energy and force were 10−6 eV and
0.005 eV Å−1, respectively. During the geometric optimizations,the bottom layers were constrained to the bulk geometry, while
the remaining layers were fully relaxed. The VESTA(Visualization for Electronic and Structural Analysis)
program42 was utilized to visualize the crystallographic, volumetric, and morphological data.
In this study, we adopted the cubic structure (space groupˉm) for CsPbBr3, the monoclinic (space group P21/m) strucPm3
ture for MAPbBr3, and the tetragonal (space group I41/a) structure for BaWO4. The atomic structures and lattice parameters
derived from first-principles simulations are provided in

2662 | Inorg. Chem. Front., 2024, 11, 2661–2671

Inorganic Chemistry FrontiersFig. S1 and Table S1,† exhibiting excellent agreement with thecorresponding experimental results.43–45 Following the rigorous lattice matching principle, the (200) in-plane latticespacing in BaWO4 closely matched those of CsPbBr3 and
MAPbBr3, serving as the foundation for constructing the perovskite/BaWO4 heterostructures. The perovskite (200) slabs
were constructed employing a stoichiometric six-layer slab,
while the BaWO4 (200) slab was generated using an elevenlayer symmetric slab. CsPbBr3 (or MAPbBr3) exhibits two
potential surface terminations: the termination by Cs (or MA)
cations, and the termination by Pb cations. In contrast, theBaWO4 slab features two distinct surface types: BaW- andO-terminated surfaces. By combining the perovskite and
BaWO4 slabs, we generated a total of eight lattice-matchedinterfacial configurations, as depicted in Fig. 1. The lattice
parameters and mean absolute strain values for the eightmodels are presented in Table S2.†The CsPbBr3/BaWO4 heterostructure was prepared throughan in situ synthesis thermal-assisted method. The stoichiometric proportions of Na2WO4·2H2O (1 mmol) and Ba(NO3)2(1 mmol) were dissolved in a 20 ml aqueous solution andstirred in a 50 ml beaker, immediately resulting in a white
BaWO4 precipitate. After centrifugation and drying, 145 mg of
the precipitate was weighed and put together with PbBr2(0.8 mmol) into a three-neck flask with 20 ml of octadecene as
the solvent, then heated to 120 °C with nitrogen protection;
the air and water impurities in the three-neck flask wereextracted. The reaction mixture was kept for 30 min, heated up
to 180 °C, and immediately infused with 3 ml of Cs-OA toobtain a yellow solution, which was reacted for 10 seconds.
The solution was cooled to room temperature with a coldwater bath, and the precipitates were centrifuged and washedwith n-hexane three times, toluene twice, anhydrous ethanol
once, and finally vacuum dried at 60 °C for 8 hours, to obtain
the CsPbBr3/BaWO4 heterostructure.

3. Results and discussion
3.1.

Interfacial adhesion

The work of adhesion (Wad)46–48 is commonly employed tocharacterize the interfacial stability and bonding strength. The
work of interfacial adhesion can be described as the reversibleenergy necessary to divide the heterostructure into two freesurfaces, quantified by the following equation:
W ad ¼ ½EPVK þ EBWO  Etotal =A

ð1Þwhere EPVK and EBWO correspond to the total energy of the
fully relaxed perovskite and BaWO4 slabs, respectively. Etotal
represents the total energy of the perovskite/BaWO4 interface,
while A specifies the interface area. It is widely accepted that ahigher Wad value corresponds to enhanced bonding strength.
The calculated Wad values of the CsPbBr3/BaWO4 and
MAPbBr3/BaWO4 heterostructures are compared in Table 1.
The formation of all eight observed interfacial configurations
is facilitated by the positive adhesion work. The perovskite/

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Fig. 1 Schematic illustration of the perovskite/BaWO4 interfaces: (a) BaW/CsBr, (b) OO/CsBr, (c) BaW/PbBr, (d) OO/PbBr, (e) BaW/MABr, (f ) OO/
CsBr, (g) BaW/MAPb, and (h) OO/MAPb.

Table 1 Calculated adhesion work (eV Å−2), charge transfer (e), planeaveraged electrostatic potential diﬀerence (eV) and work function (eV)of the relaxed perovskite/BaWO4 interfaces

Interface

Adhesion
work

Chargetransfera

Potential
diﬀerenceWorkfunction

BaW/CsBr
OO/CsBr
BaW/PbBr
OO/PbBr
BaW/MABr
OO/MABr
BaW/MAPb
OO/MAPb

0.018
0.024
0.035
0.008
0.036
0.014
0.052
0.026

−0.2
2.0
−1.5
1.8
−0.6
0.7
−1.4
1.9

2.0
1.0
2.0
1.0
1.0
−0.5
1.0
−0.5

2.8
6.7
2.6
6.5
2.8
6.7
2.5
6.7

a
The positive values indicate charge transfer from perovskite to
BaWO4, whereas the negative values exhibit charge transfer from
BaWO4 to perovskite.

BaWO4 interface exhibits larger Wad values when compared to
the weak perovskite/MXene system,30 while exhibiting equivalent Wad values to the strong perovskite/Ga2O3 system,31
thereby suggesting a high degree of interface stability. Amongthem, the MAPbBr3/BaWO4 interface exhibits larger Wadvalues, ranging from 0.014 to 0.052 eV Å−2, when compared tothose of the CsPbBr3/BaWO4 interface, which span from 0.008
to 0.035 eV Å−2. This comparison further suggests that the
MAPbBr3/BaWO4 structure possesses a relatively higher degreeof stability. The comprehensive investigations indicate that theWad values at the interfaces between BaW- and Pb-termin-This journal is © the Partner Organisations 2024

ations are higher compared to the other three interfaces,
regardless of CsPbBr3/BaWO4 and MAPbBr3/BaWO4. Therefore,
the formation of BaW/PbBr and BaW/MAPb interfaces wasmore facile compared to their counterparts in experiments.
The stability of the interface correlates with the extent of
atomic rearrangement.
To clarify the bonding mechanism in the perovskite/BaWO4heterostructures, the electron localization function (ELF),49 as
well as the atomic structures of CsPbBr3/BaWO4 and MAPbBr3/
BaWO4 systems, was analyzed, as shown in Fig. 2. In the colorimetric representation of electron localization, red is used torepresent electrons with a high degree of localization, whileblue is used to represent electrons with a high degree of delocalization. Localization and delocalization represent the
spatial distribution patterns of electrons within the system.
Localization signifies the concentration of electron density in
specific regions, whereas delocalization denotes the free movement of electrons throughout the system, indicating enhanced
electron mobility. The nearly spherical electron distribution
indicates the strong ionic bonding character between Pb andBr atoms. In contrast, the BaWO4 side exhibits the covalentbonding for the WO4 anions and the ionic bonding characterfor the Ba cations. The MAPbBr3/BaWO4 configurations withless blue area in the interface region indicate stronger interfacial interaction than the CsPbBr3/BaWO4 configurations.
Upon closer inspection of the interface region, noticeable distortions of the Pb-Br6 octahedra in the cubic structure can beobserved.50 These distortions are attributed to the strong inter-

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Inorganic Chemistry FrontiersFig. 2 ELF of the relaxed perovskite/BaWO4 interfaces: (a) BaW/CsBr, (b) OO/CsBr, (c) BaW/PbBr, (d) OO/PbBr, (e) BaW/MABr, (f ) OO/CsBr, (g)BaW/MAPb, and (h) OO/MAPb.

actions between BaWO4 and perovskite. Moreover, theCsPbBr3/BaWO4 configurations undergo more significant distortions compared to the MAPbBr3/BaWO4 configurations.
Among the various terminations, the BaW/PbBr and BaW/
MAPb configurations with the highest Wad values demonstrate
more significant distortions compared to their counterparts,
which is coincident with the results in Table 1. To provide aquantitative measure of charge transfer between perovskite
and BaWO4, we conducted Bader charge analysis51 on representative atoms. The values of calculated charge transfer arepresented in Table 1. The charge transfer direction is significantly influenced by the surface termination, irrespective of
the CsPbBr3/BaWO4 or MAPbBr3/BaWO4 systems. Specifically,
the BaW/perovskite (BaW/CsBr, BaW/PbBr, BaW/MABr, and
BaW/MAPb) configurations exhibit electron transfer from
BaWO4 to the perovskite layer, whereas the OO/perovskite (OO/
CsBr, OO/PbBr, OO/MABr, and OO/MAPb) configurations indicate charge transfer from the perovskite to the BaWO4 layer.
The above results can be attributed to the interfacial bonding
between perovskite and BaWO4.
3.2.

Electronic structures

To thoroughly elucidate the intricate characteristics of interface coupling and charge redistribution within the perovskite/
BaWO4 heterostructures, we explored the z-axis dependence ofthe three-dimensional and plane-averaged charge density
diﬀerence (Δρ).52 The yellow-colored segment signifies charge

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accumulation, whereas the cyan-colored segment denotes
charge depletion. Fig. 3 suggests that the interface region is
the primary site for charge transfer and redistribution. The
magnitude of the charge distribution at the interface is significantly influenced by the strength of the interfacial interaction.
The BaW/PbBr and BaW/MAPb configurations exhibit denser
electron isosurfaces compared to the other configurations,consistent with their highest Wad values listed in Table 1. The
plane-averaged charge density diﬀerence curves obtained from
isosurfaces exhibit distinct trends depending on various
surface terminations. The curves of the OO/perovskite (OO/
CsBr, OO/PbBr, OO/MABr, and OO/MAPb) configurations
exhibit a similar pattern, with electron accumulation on the
BaWO4 side and depletion on the perovskite side, indicating a
distinct contrast at the interface. In contrast, the curves of
BaW/perovskite (BaW/CsBr, BaW/PbBr, BaW/MABr, and BaW/
MAPb) configurations display an irregular distribution, signifying complex charge redistribution at the interface regions. The
above results are entirely consistent with the direction of
charge transfer presented in Table 1. The OO/perovskite configurations are bonded with the Cs–O and Pb–O bonds. Such
configurations under O-rich conditions contain more interfacial bonds and exhibit distinct charge redistributions at theinterface. The accumulation of various carriers at the interfaces on both ends of the heterointerface leads to the formation of a built-in electric field, which is directed from thehole accumulation region to the electron accumulation area.53

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Fig. 3 Plane-averaged electron density diﬀerence Δρ(z) and 3D charge density diﬀerence (0.002 e Å−3) of the relaxed perovskite/BaWO4 interfaces:(a) BaW/CsBr, (b) OO/CsBr, (c) BaW/PbBr, (d) OO/PbBr, (e) BaW/MABr, (f ) OO/CsBr, (g) BaW/MAPb, and (h) OO/MAPb.

To oﬀer a comprehensive assessment of electronic transport
behavior at the perovskite/BaWO4 heterostructures, the planeaveraged electrostatic potentials in the vertical direction wereanalyzed and are plotted in Fig. 4. The band alignment andthe work function of the perovskite/BaWO4 heterostructures
can be estimated via the electrostatic potentials.54 Evaluationof the potential oﬀset and work function of the heterostructures is based on the theoretical framework of the planeaveraged electrostatic potentials. When two distinct surfaces
come into contact and create heterostructures, the disparity in
Fermi energy leads to electron transport at the heterointerface,resulting in band oﬀsets. As shown in Fig. 4, a notable contrast
exists in the atomic arrangements of perovskite and BaWO4,
with atoms near the interface undergoing substantial
migration toward their final stable state, ultimately leading toa macroscopic discrepancy in the plane-averaged electrostatic
potentials. The plane-averaged electrostatic potential diﬀerence (ΔV) between the perovskite and BaWO4 was estimatedand is summarized in Table 1. The positive value indicatesthat the plane-averaged potentials of the BaWO4 side arehigher than those at the perovskite side. The potential oﬀset,
influenced by the atomic configurations near the interface,
plays a crucial role in shaping the electronic barrier and ultimately aﬀects the device performance.55 The BaW/perovskite
configurations display greater ΔV compared to the OO/perovskite configurations, irrespective of whether CsPbBr3 or
MAPbBr3 is involved. Simultaneously, the CsPbBr3/BaWO4 configurations show a larger ΔV compared to the MAPbBr3/BaWO4
configurations. In particular, for the OO/MABr and OO/MAPb
configurations, negative ΔV values are observed, indicating areversal in the potential oﬀset. The work function signifies theThis journal is © the Partner Organisations 2024

minimum energy needed to extract electrons from the Fermi
level to reach the vacuum level. Table 1 details the work functions of the corresponding perovskite/BaWO4 heterostructures.
Importantly, the work functions of the OO/perovskite configurations undergo substantial modulation towards higher values,
presenting a stark contrast to the work function observed in
the BaW/perovskite configurations. The results of potential
diﬀerences and work function measurements exhibit a highdegree of consistency with the charge transfer data outlined inTable 1. The considerably altered work function indicates that
surface engineering holds promise as an eﬀective approach forachieving ohmic contact of n- and p-type.
The density of states (DOS) provides a quantitative description of the electronic states in diﬀerent orbitals, which isessential for a comprehensive understanding of the interfacial
bonding mechanism. For a more in-depth exploration of theperovskite/BaWO4 heterostructures, we calculated anddepicted the atom-projected DOS in Fig. 5. More details of thecalculated DOS for CsPbBr3, MAPbBr3, and BaWO4 in the bulk
phase are plotted in Fig. S2.† As a member of the scheelitefamily, BaWO4 has a larger band gap compared to CsPbBr3 (orMAPbBr3).56 The calculated DOS of the perovskite/BaWO4heterostructures shows that the top of the valence band isentirely composed of O 2p and Br 4p orbitals while the bottomof the conduction band is dominated by the W 5d orbitals.
The formation of the perovskite/BaWO4 heterointerface is aconsequence of the hybridization of Br 4p and W 5d states.
The eight diﬀerent interfacial configurations exhibit similar
DOS features. The OO/perovskite configurations are identified
as belonging to a type-II heterostructure, with the conduction
band minimum (CBM) contributed by the perovskite and theInorg. Chem. Front., 2024, 11, 2661–2671 | 2665

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Fig. 4 Plane-averaged electrostatic potential of the relaxed perovskite/
BaWO4 interfaces: (a) CsPbBr3/BaWO4 and (b) MAPbBr3/BaWO4.

valence band maximum (VBM) contributed by BaWO4. A close
examination of the top of the valence band reveals that the O 2p
and peaks move toward the lower energy region for the BaW/perovskite configurations. In particular, the BaW/PbBr and BaW/
MAPb configurations exhibit the largest peak shift,57 suggestingenhanced binding energy between the two materials at the interface. The observation of interfacial defect states across the band
gap of the BaW/perovskite configurations also suggests thathybridization is enhanced at the interface. Hence, the typical
type-II band alignment observed in the OO/perovskite configur-

2666 | Inorg. Chem. Front., 2024, 11, 2661–2671

Fig. 5 DOS of the relaxed perovskite/BaWO4 interfaces: (a) CsPbBr3/
BaWO4 and (b) MAPbBr3/BaWO4.

ations was transformed into the typical type-I band alignment in
the BaW/perovskite configurations. This is consistent with theresults of charge transfer, potential diﬀerence and work function
as outlined in Table 1. The findings imply that the electronic
structures of the perovskite/BaWO4 heterostructures are dependent on the surface termination of BaWO4, not that of perovskite.
The surface termination of BaWO4 has crucial potential significance in the transformation of a type-I heterostructure to a type-II
heterostructure.

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3.3.

Optical properties

The light absorption coeﬃcient of the perovskite/BaWO4heterostructures is a key parameter for evaluating their opticalresponse to sunlight. The absorption spectra of the CsPbBr3/
BaWO4 and MAPbBr3/BaWO4 heterostructures are calculated
and displayed as in Fig. 6. For comparison, the light absorption spectra of CsPbBr3, MAPbBr3, and BaWO4 in the bulk
phase were calculated, which are shown in Fig. S3.† The
shapes of the absorption curves of CsPbBr3/BaWO4 and
MAPbBr3/BaWO4 heterostructures are quite similar. The
optical absorption spectrum of the heterostructures shows
three distinct peaks at 3.5, 5.5, and 9.5 eV. The first peak at 3.5
eV is primarily due to the transition from Br 4p to Pb 6p states
between the conduction and valence bands.58 The second
peak around 5.5 eV is attributed to the optical transition fromO 2p orbitals to W 5d orbitals. The third peak around 9.5 eVoriginates from the transition from hybridized W 5d and O 2p
states to W 5d states.59 A close inspection of the absorption
spectra reveals that the absorption intensity of the perovskite
exhibits a similar trend for both CsPbBr3/BaWO4 (BaW/CsBr >OO/CsBr > BaW/PbBr > OO/PbBr) and MAPbBr3/BaWO4 (BaW/
MABr > OO/MABr > BaW/MAPb > OO/MAPb). The BaW/CsBrheterostructure (or BaW/MABr) exhibits the lowest interfacial
distortion and remarkably well-preserved perovskite-type struc-Research Article
tures, leading to a significantly higher absorption coeﬃcient.
These results suggest that the optical properties of the perovskite/BaWO4 heterostructures are significantly aﬀected by thesurface termination of the perovskite layers, but not the
BaWO4 layers. To improve the device performance throughinterface modification, focusing on the perovskite layer should
be a promising strategy.
3.4.

Experimental verification

The CsPbBr3/BaWO4 heterostructure was successfully fabricated to further verify the first-principles predictions. The
X-ray diﬀraction (XRD) patterns of CsPbBr3, BaWO4, and
CsPbBr3/BaWO4 are displayed in Fig. 7. The XRD patternshowed diﬀraction peaks at 2θ values of 15.1°, 21.3°, 30.6°,
37.7°, and 43.6° corresponding to the (100), (110), (200), (211),and (220) phases of the typical cubic CsPbBr3, respectively.60,61
In addition, the diﬀraction peaks at 17.3°, 27.9°, 31.7°, 42.8°,
45.6°, and 53.5° are attributed to the (101), (112), (200), (204),(220), and (312) phases of the tetragonal BaWO4, respectively.62
All diﬀraction peaks are consistent with the crystalline phaseof CsPbBr3 (JCPDS No. 18-0364) and BaWO4 (JCPDS No. 430646). The results showed that CsPbBr3 and BaWO4 exhibitedhigh crystallinity with well-maintained cubic perovskite andFig. 7 Experimental XRD patterns of CsPbBr3, BaWO4, and CsPbBr3/
BaWO4.

Fig. 6 Absorption coeﬃcients of the relaxed perovskite/BaWO4 interfaces: (a) CsPbBr3/BaWO4 and (b) MAPbBr3/BaWO4.

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Fig. 8

FT-IR patterns of CsPbBr3, BaWO4, and CsPbBr3/BaWO4.

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Fig. 9SEM images of (a) BaWO4, (b) CsPbBr3/BaWO4, and (c) CsPbBr3; TEM images of (d) BaWO4, (e) CsPbBr3/BaWO4, and (f ) CsPbBr3.

tetragonal scheelite crystal phases during the formation of the
CsPbBr3/BaWO4 heterostructures.
To evaluate the chemical bond formation and interactions,
FT-IR spectral analysis of CsPbBr3, BaWO4, and CsPbBr3/
BaWO4 was performed and the results are displayed in Fig. 8.
The spectrum of BaWO4 reveals a vibrational mode at
820 cm−1, associated with asymmetric W–O vibrations, thereby
confirming the presence of the typical WO4 in the prepared
BaWO4 material.63,64 The additional absorption peak of
BaWO4 around 1400 cm−1 may be attributed to the stretchingvibrations of the organic groups present in the precursor. Twosmall peaks are recognized around 1600 and 2900 cm−1 in the
spectrum of CsPbBr3. The peak at 1600 cm−1 can be assigned
to the N–H bending vibrations of the ligands, whereas thepeak at 2900 cm−1 is associated with the oleyl group.65 The
FT-IR analysis confirms the formation of the CsPbBr3/BaWO4heterostructures.
The structural features of the prepared CsPbBr3/BaWO4heterostructures were carefully identified by scanning electron
microscopy (SEM) and transmission electron microscopy(TEM), as demonstrated in Fig. 9. The TEM images clearly
depict the CsPbBr3 and BaWO4 materials. Specifically, the analysis indicates that the interplanar spacings of 2.9 Å correspond to the CsPbBr3 (200) plane,66 whereas the interplanar
spacings of 2.7 Å correspond to the BaWO4 (200) plane,67
respectively. The confirmation of lattice-matched growth
between CsPbBr3 and BaWO4 is intricately validated throughTEM observations, closely aligning with the predictions
derived from first-principles calculations.

4.

Inorganic Chemistry Frontiers

Conclusions

To summarize, first-principles and experimental studies were
employed to investigate the interfacial properties between per-2668 | Inorg. Chem. Front., 2024, 11, 2661–2671

ovskite and BaWO4. The interfacial properties include atomic
arrangement, adhesion work, charge redistribution, potential
diﬀerence, work function, and their orbital hybridization, as
well as their optical absorption. The results indicate that the
MAPbBr3/BaWO4 configurations possess stronger interfacialinteraction than the CsPbBr3/BaWO4 configurations. The formation of BaW/PbBr and BaW/MAPb configurations was more
facile compared to their counterparts. Our study highlights theimportance of surface termination for the interfacial properties. The interfacial charge transfer direction, potential
diﬀerence, and band alignment of the perovskite/BaWO4heterostructures were found to be significantly influenced by
the surface termination of BaWO4. The absorption intensity ofthe perovskite/BaWO4 heterostructures is significantly aﬀectedby the surface termination of the perovskite. The lattice-matching growth of CsPbBr3/BaWO4 was achieved and the existenceof the heterostructure was confirmed by XRD, SEM, and TEM
characterization. This study helps us to gain better insight into
the nature of the perovskite/BaWO4 heterostructures, thereby
laying the groundwork for the realization of high-performance
perovskite-based devices.

Conﬂicts of interest
The authors declare that they have no known competing financial interests or personal relationships that could haveappeared to influence the work reported in this paper.

Acknowledgements
This work was supported by the National Natural Science
Foundation of China (Grant No. 12381240132), the China
Scholarship Council (Grant No. 202308410380), theThis journal is © the Partner Organisations 2024

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Postgraduate Education Reform and Quality Improvement
Project of Henan Province (Grant No. YJS2023JD60), and theHenan International Joint Laboratory of Nanocomposite
Sensing Materials.

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