RESEARCH ARTICLE
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Phase Engineering for Stability of CsPbI3 Nanowire
Optoelectronics
Dengji Li, Pengshan Xie, Yuxuan Zhang, You Meng, Yancong Chen, Yini Zheng,
Weijun Wang, Di Yin, Bowen Li, Zenghui Wu, Changyong Lan, SenPo Yip, Dangyuan Lei,
Fu-Rong Chen, and Johnny C. Ho*been developed to achieve in-plane
growth of 1D structures, including
capillary-bridge-manipulated
epitaxy,[2]graphoepitaxy,[3] and van der Waals
epitaxy.[4] Typically, the VLS growth mode,[5]which involves the initial seeding of metallic catalytic nanoparticles to facilitate theprocess, has realized the out-of-planeand bottom-up synthesis route, opening
up a new pathway for the 1D perovskite
electronics and optoelectronics.
Iodine-based inorganic halide perovskites (IHPs) have gained recognition
as highly suitable candidates for practicaloptoelectronics, primarily due to theirnarrower bandgap and broader spectrum
absorption.[6] However, a signiﬁcant challenge arises as the surface-to-volume ratio
increases with shrinking size, resulting in intensiﬁed surface defects that eventually dominate the environmental phase stability of CsPbI3 NWs.[7] Essentially, the black phase (𝛼, 𝛽, and 𝛾)
of CsPbI3 NWs tends to undergo a strong transformation to
the yellow phase (𝛿, non-perovskite structure) at room temperature (RT).[8] In previous research, diverse strategies, such as surface modiﬁcation and the introduction of other metal dopants,
have been utilized to achieve the stabilization of the blackphase in CsPbI3 NWs.[9] In general, introducing Zn dopants
has been documented as an eﬃcient means to curb vacancy
formation within halide perovskites,[11] reducing surface defects
and impeding degradation triggered by external factors. The intriguing query arises as to whether this speciﬁc cation doping approach can equally impede the detrimental phase conversion of CsPbI3 , ensuring the operational phase stability of
CsPbI3 NWs.
In this study, we utilized density functional theory (DFT) calculations to anticipate that the Zn dopants not only suppress
the vacancy formation but also stabilize the black phase structure for CsPbI3 NWs. Through the VLS routes, we successfully
designed and realized the out-of-plane growth of Zn-doped andself-catalyzed CsPbI3 NWs. The beneﬁcial eﬀect of Zn doping on
the CsPbI3 NWs was conﬁrmed via a series of surface characterization technologies. Moreover, photodetector devices utilizingthese two types of NWs were also manufactured, showcasing the
beneﬁcial impact of Zn doping on the optoelectronic characteristics of pure CsPbI3 . Importantly, we revealed the polarizationsensitive characteristics of stable CsPbI3 NWs, illustrating theZinc (Zn) has arisen as a signiﬁcant suppressor of vacancy formation in halide
perovskites, establishing its pivotal role in defect engineering for thesematerials. Herein, the Zn-catalyzed vapor-liquid-solid (VLS) route is reported
to render black-phase CsPbI3 nanowires (NWs) operationally stable at room
temperature. Based on ﬁrst-principle calculations, the doped Zn2+ can not
only lead to the partial crystal lattice distortion but also reduce the formationenergy (absolute value) from the black phase to the yellow phase, improving
the stability of the desired black-phase CsPbI3 NWs. A series of contrast tests
further conﬁrm the stabilization eﬀect of the Zn-doped strategy. Besides, thepolarization-sensitive characteristics of black-phase CsPbI3 NWs are revealed.
This work highlights the importance of phase stabilization engineering for
CsPbI3 NWs and their potential applications in anisotropic optoelectronics.

The crystallization of halide perovskites (HPs) into 1D structures
has generated considerable research interest for their promisingprospects in studying electron transport characteristics and multifunctional nanoscale devices.[1] To date, various strategies have
D. Li, P. Xie, Y. Zhang, Y. Meng, Y. Chen, Y. Zheng, W. Wang, D. Yin, B. Li,
Z. Wu, D. Lei, F.-R. Chen, J. C. Ho
Department of Materials Science and Engineering
City University of Hong Kong
Kowloon 999 077, Hong Kong
C. LanState Key Laboratory of Electronic Thin Films and Integrated Devices
University of Electronic Science and Technology of China
Chengdu 610 054, China
S. Yip, J. C. Ho
Institute for Materials Chemistry and Engineering
Kyushu University
Fukuoka 816 8580, Japan
E-mail: johnnyho@cityu.edu.hk
J. C. Ho
Department of Materials Science and Engineering, and State Key
Laboratory of Terahertz and Millimeter Waves
City University of Hong Kong
Kowloon 999077, Hong Kong
© 2024 The Authors. Advanced Functional Materials published by
Wiley-VCH GmbH. This is an open access article under the terms of theCreative Commons Attribution-NonCommercial-NoDerivs License,
which permits use and distribution in any medium, provided the original
work is properly cited, the use is non-commercial and no modiﬁcations
or adaptations are made.

DOI: 10.1002/adfm.202314309

Adv. Funct. Mater. 2024, 34, 2314309

2314309 (1 of 8)© 2024 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH

www.afm-journal.deFigure 1. a) Schematic diagram of the spontaneous room temperature degradation of CsPbI3 . b) Schematic diagram of the relationship between thetolerance factor (𝜏) and the B─X─B bond angle. The bottom image shows how tilting of [PbX6 ]4− octahedra is restricted with partial Pb2+ being substituted by smaller B-site cations. c) Metal─iodide bond distances for CsPbI3 and partial CsZnI3 in the optimized CsPbI3 structure. d) The distribution of
perovskites (ABX3 ) containing metal centers including Pb, Ti, Sr, Sn, Cd, Cr, Mn, and Zn in relation to the Goldschmidt octahedral constraints and thetolerance factor. The left part is calculated through ionic radius, while the other part is calculated through bond distances. e) Histograms comparing theformation energy of phase transition (ΔEform 𝛾 -𝛿 ) in initial CsPbI3 and its doped structure with substituent 4.17% of various B-site cations. f) Schematic
diagram of the improved thermal stability of orthorhombic CsPbI3 by substituting partial Pb2+ with Zn2+ . g,h) Schematic diagram of the self-catalyzed
and Zn-catalyzed VLS NWs growth.

optoelectronic anisotropic nature of CsPbI3 NWs. Our work highlights the importance of impurity doping engineering for CsPbI3
NWs and their further applications in anisotropic electronics.
According to previous research,[8] the metastable 𝛾 phase of
CsPbI3 will degrade spontaneously to the stable 𝛿 phase at RT(Figure 1a). Viewing from the environment, the degradation process of halide perovskite materials generally commences due
to defects stemming from halide vacancies. These structuralimperfections display a pronounced aﬃnity for water and oxy-Adv. Funct. Mater. 2024, 34, 2314309

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gen molecules; even a minimal concentration of such defects
yields signiﬁcant adverse eﬀects.[10] Notably, leveraging its compact ionic radius and low electronegativity, incorporating Zn
dopants has demonstrated a compelling capacity to mitigate vacancy formation.[11] This leads to a reduction in defect sites, consequently enhancing the stability of Zn-doped perovskite structures.
In essence, one signiﬁcant structural aspect that inﬂuence theRstability is the Goldschmidt’s rule, 𝜏 = √ A−X . Herein, RA−X
2RB−X

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www.afm-journal.dedenotes the separation between the A-site cation and the X-siteanion, whereas RB−X signiﬁes the spacing between the B-site
cation and the X-site anion (Figure 1b). The dimensions of the[BX6 ]4− octahedra and the cubo-octahedral voids with regard to
the A-site cation are inﬂuenced by the B-site cation. Under ideal
conditions, a 180° bond angle between B−X−B is achieved, resulting in a cubic perovskite phase with a tolerance factor (𝜏) of
1.[12] However, for CsPbI3 , the Cs2+ ion is much smaller than the
cubo-octahedral void size, resulting in a 𝜏 value of <1. As a result,the [PbI6 ]4− octahedra undergoes rotation and tilt to minimize theexcess space around the Cs2+ ion, causing the bond angle (𝜃) tobe <180°.[13] But with partial Pb2+ being substituted by smaller
B-site cations, the dimensions of the [BX6 ]4− octahedra can be
reduced, thus decreasing the void’s size and realizing the whole
structure’s relative stability.
To shed light on the octahedral rotation process, DFT calculation was carried out to predict the lattice structure of theinitial 𝛾 phase CsPbI3 and its doped phase with partial substituents, including Cd2+ , Cr2+ , Mn2+ , Sn2+ , Sr2+ , Ti2+ , and Zn2+
(Figure 1d; Figure S1, Supporting Information). Typically, thesubstituent [ZnI6 ]4− octahedra exhibits remarkable distortion in
the optimized model, greatly hindering the further tilting or rotation of octahedra to achieve the stabilization of the black phase(Figure 1b). The localized distortion within the CsPbI3 lattice results in an asymmetrical diﬀerential charge density encompassing Zn (Figure S2, Supporting Information). The speciﬁc geometry for Pb and distorted Zn octahedra are provided in Figure 1c.
Meanwhile, the ionic radii constraints for the B2+ and I− sites
to stabilize octahedral coordination were also considered for all
doped structures. More importantly, the formation energy ofphase transition (ΔEform 𝛾 -𝛿 , deﬁned as the energy change from𝛾 phase to 𝛿 phase) was calculated and displayed in Figure 1e,indicating the suppression eﬀect of Zn substitution to the deteriorative phase transition compared to initial perovskites and other
doped structures. Hence, all calculated results suggest a promising prospect of the Zn doping strategy to stabilize the CsPbI3
NWs (Figure 1f).
Inspired by the above analysis and calculations, initial CsPbI3
and Zn-doped NWs design follow a VLS route based on chemical
vapor deposition (CVD). Figure 1g,h depict schematic diagramsof the VLS growth process. The detailed NW growth process canbe found in the Methods section, and a schematic diagram of
the growth system is provided in Figure S3 (Supporting Information). Notably, the self-catalyzed VLS growth involves the formation of Pb seeds driven by surface energy induced by surface
roughness, while the Zn nanocatalysts are synthesized througha drop-coating process. The dark ﬁeld optical image of the substrate full of Zn nanoparticles is provided in Figure S4 (Supporting Information).
To verify the growth morphology and mechanism of the obtained NWs, the samples synthesized from these two routes wereobserved through a scanning electron microscope (SEM). As
shown in Figure S5 (Supporting Information), the designed perovskite NWs from both routes were grown vertically (i.e., out ofplane) on the substrate. Furthermore, as depicted in Figure S6(Supporting Information), distinctive ﬂower-like and sphericalcatalytic seeds can be observed in the tip region of each individual NW from the Zn-doped and self-catalyzed routes, respectively. Furthermore, the elemental distribution of the fabricatedAdv. Funct. Mater. 2024, 34, 2314309

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nanowire samples was examined through energy-dispersive Xray spectroscopy (EDS) mapping (Figure 2a,b), revealing that theﬂower-like catalyst apex of the Zn-doped NW is primarily consisting of Zn. In contrast, the spherical catalytic seed of the selfcatalyzed NW consists predominantly of Pb. Meanwhile, Cs, Pb,
and I exhibit uniform distribution in the NW body for both samples. This result is expected as the melting temperatures of both
the Zn-Pb alloying (183–245 °C) and pure lead (327.5 °C) are relatively low,[14] enabling the formation of liquid metal seeds together with a highly eﬀective supersaturation mechanism occurring at the catalyst apex. On the other hand, the result reveals thelimited solubility of the Cs and I at equilibrium in the liquid Zn
and Pb during the growth of NWs. Hence, the NWs from these
two routes have been veriﬁed as VLS growth. Composition quantiﬁcation of the Zn-doped NWs was carried out along the axial
axis of the NW (Figure 2c), conﬁrming the uniform dispersion ofCs, Pb, and I elements within the NW body with a compositionalratio of 1:1:3, aligning with the stoichiometric ratio of CsPbI3 .
Next, to verify the crystal phase of these two obtained perovskite NWs, X-ray diﬀraction (XRD) was ﬁrst carried out. As
shown in Figure 2d, the main peaks of both NWs agree withthe orthorhombic CsPbI3 (Pnma (62), a = 8.856 Å, b = 8.576 Å,
c = 12.472 Å).[15] The theta shift of peaks caused by Zn dopants
was also noticed, indicating a smaller crystalline structure thanthe pristine CsPbI3 . Moreover, as depicted in scanning transmission electron microscopy (STEM) images (Figure S5, Supporting Information), the Zn-catalyzed CsPbI3 NWs demonstrate signiﬁcantly improved morphology compared to the self-catalyzed
NWs, which exhibit irregular distortion and partial breakage incertain sections of their structure. The experimental results directly demonstrate the optimized eﬀect of Zn-doping engineering on the environmental stability of CsPbI3 NWs. Meanwhile,
the acquired high-resolution TEM (HRTEM) image in Figure S7a(Supporting Information) conﬁrms the orthorhombic phase of
CsPbI3 (Pnma (62)), which is further supported by the selectedarea electron diﬀraction (SAED) pattern shown in Figure S7b(Supporting Information), where the NW body’s pattern corresponds to the (001) plane of the orthorhombic phase. These ﬁndings align well with the XRD results depicted in Figure 2d. Importantly, the orthorhombic perovskite structure of Zn-catalyzed
CsPbI3 NWs remains stable at room temperature, mainly due tothe combined eﬀect of substituted Zn2+ to Pb2+ and the larger
I− ionic radius compared to other halide ions.[16] Besides, theSAED pattern also reveals that the Zn-seeded CsPbI3 NWs tend
to grow along the [100] direction, aligning with prior experimental and computational investigations. This preference for growthalong the (100) planes of CsPbI3 NWs can be due to their reduced
surface free energy compared to other crystallographic planes,
which drives directed crystal growth.[17] In summary, the analysis of the structure and elements conﬁrms that the acquired NW
samples were CsPbI3 orthorhombic phase grown following the
VLS mechanism.
To investigate the impact of Zn impurity doping on the inherent properties of perovskites, we conducted photoluminescence(PL) measurements and analysis on samples of self-catalyzed
and Zn-seeded CsPbI3 NWs. As depicted in Figure 2e, the selfcatalyzed CsPbI3 NW exhibited a complete emission with full
width at half-maximum (FWHM) of 31 nm, centered at 702 nm(≈1.766 eV), while the emission peak of Zn-seeded samples© 2024 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH

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www.afm-journal.deFigure 2. Materials characterization of the two types of CsPbI3 NWs. a,b) EDS mapping of the Zn-catalyzed and self-catalyzed CsPbI3 NWs. c) EDS
line scan of the Zn-doped CsPbI3 NWs. d) XRD spectra comparison of the Zn-catalyzed and self-catalyzed NWs. e) PL spectra of the two types of NWs.
f–i) XPS spectra of the two types of CsPbI3 NWs.

displayed a ≈6 nm blue shift. Previous theoretical studies haveindicated that the CsPbI3 lattice contracts due to the substitution of smaller Zn2+ cations for Pb2+ , also consistent with theobserved theta shift in the XRD pattern of Zn-seeded NWs.[18] At
the same time, the calculated bandgaps of Zn-doped perovskites(Figure 3e) have demonstrated a broadening, which can be attributed to a decrease in the volume of unit cell or/and an increase in electronegativity (EN) of the component species.[19]Meanwhile, the absorption and temperature-dependence PL ofperovskite NW samples, both with and without Zn dopants, were
measured to investigate the inﬂuence of Zn dopants. The results,
as illustrated in Figure S8a,b (Supporting Information), further
highlight the observed blue shift in the Zn-doped NWs, conﬁrming the eﬀect of Zn doping. The Zn-doped samples also exhibit
superior thermal stability compared to the intrinsic perovskite
samples. Notably, the intrinsic perovskite samples experience a
PL intensity reduction of over 50% as the environmental tem-Adv. Funct. Mater. 2024, 34, 2314309

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perature reaches 200 °C, whereas the Zn-doped samples demonstrate relative resilience under similar conditions.
To investigate the chemical states of Zn2+ within the NWs,
these two NWs samples were investigated using X-ray photoelectron spectroscopy (XPS). Figure 2f displays XPS peaks for
Cs, Pb, and I in both types of NWs. Notably, additional peaks
were observed in the high-resolution XPS spectra of Zn 2p asshown in Figure 2g, appearing at 1021.2 and 1043 eV in the Zncatalyzed CsPbI3 NW sample, corresponding to the Zn 2p signals originating from Zn2+ . This observation indicates the incorporation of Zn2+ ions into the structure of CsPbI3 NWs during
the VLS growth process. To explore the impact of Zn on CsPbI3
NWs further, we analyzed the high-resolution XPS spectra for Pb
4f and I 3d signals. In Figure 2h, the Pb 4f spectra of the selfcatalyzed sample exhibited characteristic peaks corresponding toPb2+ 4f7/2 and Pb2+ 4f5/2 at 138.3 and 143.2 eV, respectively. In
contrast, those peaks of the Zn-catalyzed sample shifted to lower© 2024 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH

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www.afm-journal.deFigure 3. a,b) PL mapping (inset are the optical images) and c) TRPL curves of the two types of CsPbI3 NWs. d–f) Calculated band of the initial 𝛾,
Zn-doped 𝛾 , and initial 𝛿 phase of the CsPbI3 .

energy levels. A similar shift was also observed in the I 3d spectra. The ≈0.2 eV decrease in the Pb2+ 4f and I 3d spectra of the
Zn-catalyzed sample is attributed to the presence of Zn, demonstrating the incorporation of Zn2+ ions into the CsPbI3 perovskite
lattice. Furthermore, Zn2+ exhibits a more substantial chemicalinteraction with I− compared to Pb2+ , potentially resulting in apartial weakening of the interaction between outer and core electrons in adjacent Pb2+ and I− ions.[20]To achieve a more in-depth exploration of the impact of Zn
doping on CsPbI3 NWs, we employed confocal photoluminescence (PL) mapping on both types of NWs (Figure 3a,b). The
Zn-doped CsPbI3 NWs exhibited complete and uniform PL signals across their entire bodies, while the self-catalyzed sample
showed partial darkening and fragmenting PL mappings under the same measurement conditions. Time-resolved photoluminescence (TRPL) measurements were performed on the two
types of CsPbI3 NWs. Notably, they exhibited distinct TRPL decay characteristics. The Zn-seeded NW demonstrates a singleexponential ﬁtting curve (𝜏 = 248.7 ns), while the self-catalyzed
NW exhibits a double-exponential TRPL decay characteristic(𝜏 average = Σi Ai 𝜏 i 2 /Σi Ai 𝜏 i = 36.5 ns). The simpler PL decay and in-Adv. Funct. Mater. 2024, 34, 2314309

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creased PL lifetime observed in the Zn-catalyzed NW indicate thesuppression of nonradiative recombination, indicating a lower
defect density surface compared to the self-catalyzed NW.[21] The
presence of trapping states induced by defects in the nonradiative recombination process captures photogenerated carriers andreduces their diﬀusion length, leading to inferior optoelectronic
performance.[22] Therefore, the superior surface condition of Zncatalyzed CsPbI3 NWs holds the potential for good performanceand high-speed optoelectronics.
Following that, the optoelectronic properties of the two typesof CsPbI3 NWs were investigated by conﬁguring them into
photodetector (PD) devices (detailed procedures compiled in
Figure S9 and Method section, Supporting Information).[5,23]
The speciﬁc schematic diagram and SEM image are provided in
Figure 4a,b. In the current-voltage (I-V) curves (Figure 4c) andcurrent versus time (I-t) curves (Figure 4d), the Zn-seeded CsPbI3
NW PDs exhibit ultra-low dark currents (Idark ) of ≈0.1 pA at 2 V
bias. At the same time, the self-catalyzed NW devices have darkcurrents (Idark ) that increased over 10 times. However, under a
2 mW cm−2 illumination of 450 nm laser, the photocurrent (Ilight )of Zn-catalyzed CsPbI3 NW devices increases by over 104 times to© 2024 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH

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www.afm-journal.deFigure 4. Device performance characterization. a,b) Schematic diagram and SEM image of the single NW PD device. c) I-V curve and d) I-t curve
comparison of the two types of NW PD devices. e) I-t curve of the Zn-doped PD device under diﬀerent power density illumination. f) I-P curve, g) SCLC
curve, h) response and recovery times curve comparison of the two types of NW PD devices. i) Polarization dependence of the current intensity at thebias of 2 V and light intensity of 2 mW cm−2 .

5.7 ± 0.4 nA, much higher than the self-catalyzed PD devices,at ≈10 times. Moreover, the photoresponse (Figure 4e) was investigated at various power densities (spanning from 0.02 to
6 mW cm−2 ), demonstrating a positive correlation between photocurrent and power density as more carriers are generated withan increasing photon ﬂux. All the photocurrent data for the two
types of PDs were extracted and compiled in Figure 4f, ﬁtting
perfectly to the power law equation of Iph ∝P𝛼 . The coeﬃcient 𝛼
values of Zn-doped and self-catalyzed NW PDs are calculated tobe 0.67 and 0.95, respectively, indicating an ideal trap-free characteristic of Zn-doped NWs.[24]To evaluate the optoelectronic performance of the two types
of NW-based PDs, the two most important ﬁgure-of-merit parameters, responsivity (R) and detectivity (D*), were calculated.
Here, R is described by the equation R = Iph /PS, where Iph (Iph =Ilight − Idark ), P, and S are the photocurrent, power density, and effective illumination area, respectively. Under the illumination of
0.02 mW cm−2 , the highest R-value for Zn-seeded CsPbI3 NWs is1935 ± 55 A W−1 (Figure S10a, Supporting Information), whichis larger than the self-catalyzed CsPbI3 NW value of 98 ± 18 A
W−1 under the same conditions. The other parameter, D* , is de-Adv. Funct. Mater. 2024, 34, 2314309

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scribed as D* = R(S Δf)1/2 /in . Here, Δf represents the electrical bandwidth, and in represents the noise current. According to
Figure S10c (Supporting Information), the noise current spectrum is primarily characterized by 1/f noise when biased at 2 V.
Moreover, there is a noticeable noise enhancement from 1.53 fA
Hz-1/2 of Zn-catalyzed PDs to 98.44 fA Hz-1/2 of the self-catalyzed
device at 1 Hz, which can be attributed to the stabilization of Zn
impurity dopants to suppress the phase transition degradation
process. The highest D* (Figure S10b, Supporting Information)of Zn-catalyzed PDs is calculated as 5.97 × 1013 cm Hz1/2 W−1(Jones), higher than the self-catalyzed device of 4.58 × 1010 Jonesand outperforming most reported 1D perovskite devices (Figure
S10d and Table S1, Supporting Information). Furthermore, afast response is also important for a practical PD. In essence,
the response time is mainly dominated by photogenerated carriers’ separation, transport, and collection eﬃciency.[25] To acquire the high-precision photoresponse, a current ampliﬁer anddigital oscilloscope were connected to the device to record thehigh-speed signals achieved by a 800 Hz chopper.[26] As depicted
in Figure 4f, the Zn-catalyzed CsPbI3 NW exhibits an impressively fast photoresponse of 208 μs, surpassing the self-catalyzed© 2024 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH

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CsPbI3 NW with 325 μs, as well as most of the reported 1D
perovskite (Table S1 and Figure S10e, Supporting Information).
The signiﬁcantly higher performance of Zn-catalyzed NWs canbe attributed to superior material quality, meanwhile preventing
the degradation transmission from the black phase to the yellow
phase.
Moreover, a detailed analysis of the space-charge-limited current (SCLC) results (Figure 4h) was conducted to evaluate the surface condition of NWs further. Drawing on the previous researchwork,[27] the trap-ﬁlled limit voltage (VTFL ) is primarily inﬂuenced
by the trap density (nt ) as,
VTFL =

D.L. and P.S.X. contributed equally to this research, which was ﬁnancially
supported by a fellowship grant (CityU RFS2021-1S04) and a Collaborative
Research Equipment Grant (C1015-21EF), both awarded by the Research
Grants Council of the Hong Kong Special Administrative Region, China.

Conﬂict of Interest
The authors declare no conﬂict of interest.

Data Availability Statementent L22𝜀𝜀0(1)where L, ɛ (assumed as 6.3)[28] and ɛ0 are the channel length,
the relative dielectric constant of CsPbI3, and the vacuum permittivity, respectively. The trap density, nt , of Zn-doped CsPbI3
was computed as 4.04 × 1014 cm−3 , which is lower than that ofself-catalyzed samples (1.73 × 1015 cm−3 ), signifying an improved
electron transport pathway in Zn-catalyzed CsPbI3 . Therefore, it
was demonstrated that the eﬀectiveness of the Zn doping strategy in stabilizing the CsPbI3 NWs and reducing the trap density,
ultimately optimizing the corresponding optoelectronic performance.
Moreover, the polarized photoelectric behavior of the Zndoped device was investigated further to reveal the underlying
optical anisotropy of Zn-doped CsPbI3 NWs. The polarizationdependent photoresponse measurements were performed by positioning a 1/2 polarizer before the 450 nm laser as the polarization photosource. Figure 4i and Figure S10f (Supporting Information) illustrate the corresponding polarization photoresponse
at a bias of 2 V and light intensity of 2 mW cm−2 , demonstratingvarying photocurrent intensities with the laser polarization angle from 0° to 360°. The photocurrent enhances to a maximum
at 45° and 225° polarization angles and reduces to the minimum
values at 135° and 315°. Therefore, the photoresponse anisotropy
ratio, ɛ, of the Zn-doped CsPbI3 can be calculated throughɛ = (Imax − Imin )/(Imax + Imin ) as 0.68,[29] indicating the great potential of the Zn-doped CsPbI3 NWs for the polarization-sensitive
optoelectronic devices.
In this work, the VLS growth of single-crystal CsPbI3 NWs
was achieved through self-catalyzed and Zn-catalyzed routes.
DFT calculations and a series of characterization technologies
revealed the optimization eﬀect of Zn impurity doping on
the degradation of CsPbI3 NWs. The single CsPbI3 NW was
conﬁgured into PDs, exhibiting remarkable optoelectronic performances, achieving a remarkable responsivity of 1935 A W−1 ,≈105 on/oﬀ current ratio, a detectivity of 5.97 × 1013 Jones, anda fast response time of 206 μs. Importantly, the Zn-catalyzed perovskite nanowires exhibit apparent photoresponse anisotropy,
promising for fundamental investigations and practicalapplications.

Supporting Information
Supporting Information is available from the Wiley Online Library or fromthe author.

Adv. Funct. Mater. 2024, 34, 2314309

Acknowledgements

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The data that support the ﬁndings of this study are available from thecorresponding author upon reasonable request.

Keywords
halide perovskite, nanowire, optoelectronic anisotropy, vacancy suppressor, Zn-doping
Received: November 14, 2023
Revised: December 26, 2023
Published online: January 31, 2024

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