1 Introduction
Linearly polarized light with electric field oscillations confined to a fixed plane, plays a critical role in numerous applications such as bioimaging, anti-counterfeiting technology and three-dimensional displays (; ; ; ). This polarization-dependent phenomenon enables selective material interactions while suppressing isotropic background signals, thereby achieving remarkable signal-to-noise ratios exceeding conventional limits. Traditional approaches relying on external polarizers, however, inevitably suffer from substantial energy losses (>50%) (; ), fundamentally limiting their applicability in energy-efficient devices. Such limitations have driven intensive research into directly generating polarized emission from the emissive layer of light-emitting diodes (LEDs), which promises to circumvent these efficiency bottlenecks.
The polarization characteristics of luminescence material are fundamentally governed by the transition dipole moment (TDM) orientation. Although the LEDs based on organic molecules with aligned TDMs can perform linearly polarized electroluminescence (EL), the degree of polarization (DOP) achieved actually was limited until now (<40%) (; ). On the other hand, anisotropic inorganic nanocrystals (e.g., nanorods, nanoplatelets) exhibit exceptional single-particle photoluminescence polarization with DOP values exceeding 70% (). Nevertheless, the transition from individual nanocrystals to functional films introduces critical challenges—randomized orientation distributions during solution processing dramatically degrade macroscopic polarization characteristics. This fundamental limitation highlights the urgent need for developing novel material systems capable of maintaining aligned TDM orientations in macroscopic assemblies.
Colloidal perovskite nanocrystals have recently emerged as a paradigm-shifting material platform, combining solution processability with exceptional optoelectronic properties including near-unity quantum yields and spectral tunability across the visible spectrum (; ; ). Of particular significance is their unique excitonic fine structure, characterized by bright triplet states with enhanced oscillator strengths (), coupled with spontaneous self-assembly capabilities into orientationally ordered superlattices (; ; ). From a crystallographic perspective, perovskite superlattices are macroscopic quantum state materials formed by the periodic arrangement of perovskite nanocrystals acting as “artificial atoms” in two-dimensional or three-dimensional space (). The synthesis techniques for perovskite superlattices can be divided into three main categories based on principle: self-assembly, solid-phase synthesis, and epitaxial growth (; ; ; ). These methods enable fabrication of superlattices with high structural order and tunable optical properties. These inherent attributes position perovskite superlattices as a transformative platform for realizing polarized emission sources without requiring external polarization optics. This paper introduces the strategies for manipulating TDM orientation and highlight the breakthroughs in this emerging field. In addition, critical challenges toward practical implementation of ultra-bright polarized LEDs are further discussed.
2 Manipulating transition dipole moment orientation
The photon emission characteristics in halide perovskite nanocrystals are mediated by the TDMs strength and orientation (; ). Specifically, the TDM is a vector quantity that describes the strength and direction of the electric dipole transition responsible for light absorption or emission in a material. It is correlated with the electronic Bloch states and represents the coupling between the initial and final electronic states during an optical transition. The modulus square of the transition electric dipole moment is proportional to the transition probability, and its direction determines the polarization direction of the emission (; ; ).
Emitters located within the sample plane (x–y plane) can possess both out-of-plane (OP) dipoles oriented along the z-axis and in-plane (IP) dipoles. The OP and IP dipoles contribute differently to s- and p-polarized emission: s-polarization contains only radiation from IP dipoles because the electric field oscillates perpendicular to the plane of incidence, which aligns with the IP dipole orientation. However, p-polarization contains contributions from both IP and OP dipoles since the electric field oscillates in the plane of incidence. The relative contributions of these dipoles strongly influence the radiation patterns of emitters (Figure 1a). The radiation intensity patterns are derived by convolving the TDM distribution |μ(θ,ϕ)|2 with the radiation pattern of a Hertzian dipole (). Thus, the TDM directly influences the polarization direction and intensity of emitted light.
FIGURE 1
Taking into account the interplay of electronic structure, dielectric environment and orientational distributions (Figure 1d), many strategies engineered for fine-tuning TDM orientation to enhance the emission anisotropy (; ; ; ; ; ): 1) nanocrystals geometry. Numerous theoretical and experimental researches suggest that the TDMs of anisotropic nanocrystals with reduced dimensions, especially nanoplatelets, possess high orientation compared with dots, depicted in Figure 1b (; ; ; ). Additionally, the thickness and lateral dimensions of NPLs regulate the anisotropy of Bloch states, quantum confinement, and exciton fine structure, which collectively tune the TDM orientation in electronic structure level. 2) Dielectric environment. Dielectric confinement effects modify the exciton fine structure by altering the spatial distribution and energy levels of excitons within perovskite nanocrystals. This dielectric anisotropy impacts the anisotropy of the Bloch states and consequently the TDM orientation. Variations in the local dielectric environment, such as changes in the surrounding matrix or substrate, can thus modulate the exciton radiative properties and the balance between IP and OP dipole components. For instance, when consider oleic acid ligands surrounding, the emission becomes even more directed for NPLs (Figure 1c) (). 3) Ordered assembly. Assembly dictates TDM anisotropy by controlling nanocrystals orientation and interactions. Ordered structures enhance anisotropy through aligned TDMs, while disordered systems exhibit isotropy. The specific assembly type, such as superlattice, and inter-particle coupling further modulate these effects. In this regard, Perovskite superlattices influence the transition dipole moment (TDM) primarily through their anisotropic dielectric environment and ordered assembly. The superlattice structure induces dielectric confinement and anisotropy, which modifies the local electric field distribution around the NCs, thereby affecting the orientation and magnitude of the TDM. Specifically, anisotropic NC superlattices rescale the radiation patterns of horizontal (in-plane) and vertical (out-of-plane) dipoles, enhancing light emission within the critical angle and improving light outcoupling efficiency (). Additionally, the controlled self-assembly of nanoplatelets into superlattices allows fine tuning of their orientation (face-up or edge-up), which directly governs the macroscopic TDM orientation and results in highly polarized emission (). This ordered arrangement and confinement effect enable tuning of the TDM orientation by regulating exciton fine structure and dielectric anisotropy (). Thus, perovskite superlattices can serve as a powerful platform to manipulate TDM orientation and enhance optical properties in optoelectronic devices. For example, this effect is evident in nanoplatelet solids where increasing order parameter S (introduced to quantify the uniaxial orientational distribution of a given film) from −0.5 to one shifts the average orientation from face-on to edge-on, enhancing directional emission and polarization ratio ().
3 Directed emission in perovskite superlattices
In the recent groundbreaking work, Ye et al. firstly realized direct linearly polarized EL from strongly quantum-confined CsPbI3 perovskite NPLs assembled with controlled orientation (). By manipulating the solvent evaporation rate, the authors achieved precise self-assembly of NPLs into face-down or edge-up orientations. It was found that edge-up orientations favored stronger out-of-plane dipole emission with higher DOP values and achieved a record-high degree of linear polarization (74.4%) in EL LEDs without the need for external photonic structures or polarizers. In addition, PbI2 ligand passivation was carried out to significantly boost photoluminescence quantum yield (PLQY) from ∼48% to ∼65% by mitigating trap states and non-radiative recombination pathways. This chemical treatment furtherly improved external quantum efficiencies (EQE), reaching up to 2.8%, alongside enhanced operational stability.
The study also elucidated the fundamental photophysical mechanisms contributing to the high polarization. Strong quantum and dielectric confinement in the CsPbI3 NPLs induced significant exciton fine-structure splitting (∼11–20 meV), which, combined with uniform NPL alignment, leads to highly linearly polarized PL and EL (Figures 1e,f). Interestingly, the EL polarization surpassed that of PL, a phenomenon attributed to electric-field-induced modifications of exciton states and charge transfer dynamics under device operation. This nuanced understanding opens avenues for further tailoring excitonic properties via device engineering.
Overall, this work established a comprehensive framework combining controlled nanoplatelet orientation, surface passivation, and detailed photophysical analysis to realize highly polarized and efficient EL devices. It represents a meaningful stride toward practical polarized light sources in perovskite optoelectronics and inspires future research to refine and expand these promising materials and device concepts.
Interestingly, Luo et al. demonstrated unexpected polarized superradiance arising from superlattices of CsPbBr3 quantum dots (QDs), however, each QD, being cubic in shape, inherently lacks intrinsic anisotropy in its optical properties (). In generally, without intrinsic anisotropy in the exciton transition of individual nanocrystals—like nanoplatelets and nanorods—or extrinsic anisotropy introduced by the superlattice geometry, the superlattice is not expected to perform emission anisotropy. And they conjectured that anisotropic interdot electronic coupling affected by quantum confinement (QD size) and ligand chemistry, could be responsible for the unique feature. These findings open new avenues for designing polarized coherent light sources without relying on inherently anisotropic materials, which could simplify fabrication and integration in photonic devices.
4 Discussion
The recent advancements in achieving direct polarized emission from perovskite superlattices, particularly through TDM orientation control, mark notable progress in polarized optoelectronics and hold transformative potential across multiple optoelectronic and quantum domains. Aligned dipoles in superlattices direct photon emission perpendicular to substrates, significantly boosting light extraction as well as eliminating the need for external polarizers in three-dimensional displays. In the field of lasers, polarized emission control in superlattices can significantly reduce lasing thresholds while enhancing beam quality. Moreover, through precise manipulation of dipole orientations within superlattices, macroscopic quantum state control can be achieved at room temperature, which enable to generate high-intensity, short-pulse quantum light sources ideal for supplying coherent photons in quantum communication and computing systems.
However, three critical challenges persist. First, imperfect nanoplatelet alignment and insufficient device stability under operational bias limit commercial viability. Second, the quantum mechanical origins of TDM orientation in superlattices remain ambiguous, particularly the emergence of anisotropic electronic coupling from isotropic quantum dot constituents-a fundamental barrier to rational design. Third, the structure-polarization correlation requires systematic investigation through polarization-resolved spectroscopy coupled with atomic-scale strain mapping to resolve nanoscale asymmetries in quantum dot assemblies. Addressing these challenges through advanced characterization and computational modeling will accelerate the development of high-performance polarized LEDs for next-generation photonic technologies.
Statements
Author contributions
SY: Writing – original draft, Writing – review and editing. JX: Writing – review and editing.
Funding
The author(s) declare that financial support was received for the research and/or publication of this article. Project supported by the National Natural Science Foundation of China (Nos. 12104455,12374389, 12074380), Natural Science Foundation of Fujian Province (Nos. 2022J05092), the China Postdoctoral Science Foundation (2021M703220) and Youth Innovation Promotion Association of Chinese Academy of Sciences (No.2022306).
Conflict of interest
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declare that no Generative AI was used in the creation of this manuscript.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
References
1
AchtsteinA. W.SchliwaA.PrudnikauA.HardzeiM.ArtemyevM. V.ThomsenC.et al (2012). Electronic structure and exciton–phonon interaction in two-dimensional colloidal CdSe nanosheets. Nano Lett.12 (6), 3151–3157. 10.1021/nl301071n
2
BeckerM. A.NedelcuG.SercelP. C.ShabaevA.MehlM. J.MichopoulosJ. G.et al (2018). Bright triplet excitons in caesium lead halide perovskites. Nature553, 189–193. 10.1038/nature25147
3
BlachD. D.LumsargisV. A.ClarkD. E.ChuangC.WangK.DouL.et al (2022). Superradiance and exciton delocalization in perovskite quantum dot superlattices. Nano Lett.22 (19), 7811–7818. 10.1021/acs.nanolett.2c02427
4
BlachD. D.Lumsargis-RothV. A.ChuangC.ClarkD. E.DengS.WilliamsO. F.et al (2025). Environment-assisted quantum transport of excitons in perovskite nanocrystal superlattices. Nat. Commun.16 (1), 1270. 10.1038/s41467-024-55812-8
5
BloxhamB. B.KheifetsS.CohenA. E. (2021). Linearly polarized excitation enhances signals from fluorescent voltage indicators. Biophys. J.120 (23), 5333–5342. 10.1016/j.bpj.2021.10.028
6
BolesM. A.EngelM.TalapinD. V. (2016). Self-assembly of colloidal nanocrystals: from intricate structures to functional materials. Chem. Rev.116 (18), 11220–11289. 10.1021/acs.chemrev.6b00196
7
CuiJ.LiuY.DengY.LinC.FangZ.XiangC.et al (2021). Efficient light-emitting diodes based on oriented perovskite nanoplatelets. Sci. Adv.7(41),eabg8458. 10.1126/sciadv.abg8458
8
CulliganS. W.GengY.ChenS. H.KlubekK.VaethK. M.TangC. W. (2003). Strongly polarized and efficient blue organic light-emitting diodes using monodisperse glassy nematic oligo(fluorene)s. Adv. Mater.15 (14), 1176–1180. 10.1002/adma.200304972
9
CunninghamP. D.SouzaJ. B.Jr.FedinI.SheC.LeeB.TalapinD. V. (2016). Assessment of anisotropic semiconductor nanorod and nanoplatelet heterostructures with polarized emission for liquid crystal display technology. ACS Nano10 (6), 5769–5781. 10.1021/acsnano.5b07949
10
GengJ. (2013). Three-dimensional display technologies. Adv. Opt. Photonics5 (4), 456–535. 10.1364/AOP.5.000456
11
GengY.CulliganS. W.TrajkovskaA.WallaceJ. U.ChenS. H. (2003). Monodisperse oligofluorenes forming glassy-nematic films for polarized blue emission. Chem. Mater.15 (2), 542–549. 10.1021/cm0208859
12
HuJ.LiL.-s.YangW.MannaL.WangL.-w.AlivisatosA. P. (2001). Linearly polarized emission from colloidal semiconductor quantum rods. Science292 (5524), 2060–2063. 10.1126/science.1060810
13
KoP. K.GeJ.DingP.ChenD.TsangH. L. T.KumarN.et al (2025). The deepest blue: major advances and challenges in deep blue emitting quasi-2D and nanocrystalline perovskite LEDs. Adv. Mater.37 (23), 2407764. 10.1002/adma.202407764
14
KumarS.MarcatoT.KrumeichF.LiY.-T.ChiuY.-C.ShihC.-J. (2022). Anisotropic nanocrystal superlattices overcoming intrinsic light outcoupling efficiency limit in perovskite quantum dot light-emitting diodes. Nat. Commun.13 (1), 2106. 10.1038/s41467-022-29812-5
15
LeiY.LiY.LuC.YanQ.WuY.BabbeF.et al (2022). Perovskite superlattices with efficient carrier dynamics. Nature608 (7922), 317–323. 10.1038/s41586-022-04961-1
16
LiC.LiX.LiuX.MaL.YanH.TongL.et al (2024). On-substrate fabrication of CsPbBr3 single-crystal microstructures via nanoparticle self-assembly-assisted low-temperature sintering. ACS nano18 (12), 9128–9136. 10.1021/acsnano.4c00326
17
LiangZ.CaoJ.ZhouZ.RenL.WuH.WangZ.et al (2025). Molecular sublimation enables 2D–3D transformation of orientational FAPbI3 perovskites. Nat. Synth.4, 347–358. 10.1038/s44160-024-00696-1
18
LiuC.WangX.TangZ.JiaoY.ZhaoD.LiuM.et al (2025a). Double-headed brush CsPbI3 nanorod assemblies for high non-filtered linear polarization in optical displays. Nano Energy142, 111233. 10.1016/j.nanoen.2025.111233
19
LiuH.PortniaginA. S.TangB.VighneshK.LiY.WuY.et al (2025b). Helical perovskite nanowires with strong circularly polarized luminescence self-assembled from red-emitting CsPbI3 quantum dots following chiral ligand exchange. ACS Nano19 (18), 17774–17784. 10.1021/acsnano.5c03149
20
LuoL.TangX.ParkJ.WangC.-W.ParkM.KhuranaM.et al (2025). Polarized superradiance from CsPbBr3 quantum dot superlattice with controlled interdot electronic coupling. Nano Lett.25 (15), 6176–6183. 10.1021/acs.nanolett.5c00478
21
MaP.QingY.HanB.LiC.ZhaoB.TanZ. a. (2025). Manipulating ion-dipole interaction in CsPbBr3 quantum dots for efficient and stable perovskite light-emitting diodes. Adv. Funct. Mater. n/a (n/a), 2507566. 10.1002/adfm.202507566
22
MarcatoT.KrumeichF.ShihC.-J. (2022). Confinement-tunable transition dipole moment orientation in perovskite nanoplatelet solids and binary blends. ACS Nano16 (11), 18459–18471. 10.1021/acsnano.2c06600
23
SchullerJ. A.KaraveliS.SchirosT.HeK.YangS.KymissisI.et al (2013). Orientation of luminescent excitons in layered nanomaterials. Nat. Nanotechnol.8 (4), 271–276. 10.1038/nnano.2013.20
24
ScottR.AchtsteinA. W.PrudnikauA. V.AntanovichA.SiebbelesL. D. A.ArtemyevM.et al (2016). Time-resolved Stark spectroscopy in CdSe nanoplatelets: exciton binding energy, polarizability, and field-dependent radiative rates. Nano Lett.16 (10), 6576–6583. 10.1021/acs.nanolett.6b03244
25
ScottR.HeckmannJ.PrudnikauA. V.AntanovichA.MikhailovA.OwschimikowN.et al (2017). Directed emission of CdSe nanoplatelets originating from strongly anisotropic 2D electronic structure. Nat. Nanotechnol.12 (12), 1155–1160. 10.1038/nnano.2017.177
26
ShiC.-M.LuH.WangJ.-Y.LongG.XuL.-J.ChenZ.-N. (2025). Stepwise amplification of circularly polarized luminescence in indium-based metal halides by regulating their structural dimension. Nat. Commun.16 (1), 1505. 10.1038/s41467-025-56394-9
27
SongJ.ProdanovM. F.GaoY.KangC.BhadraD.ChengY.et al (2025). Polarized color filters using colloidal quantum rod nanocrystals for advanced high-performance displays. Adv. Sci.12 (21), 2414316. 10.1002/advs.202414316
28
SrivastavaA. K.ZhangW.SchneiderJ.RogachA. L.ChigrinovV. G.KwokH.-S. (2017). Photoaligned nanorod enhancement films with polarized emission for liquid-crystal-display applications. Adv. Mater.29 (33), 1701091. 10.1002/adma.201701091
29
WangM.YangZ.ZhangC. (2021). Polarized photoluminescence from lead halide perovskites. Adv. Opt. Mater.9 (23), 2002236. 10.1002/adom.202002236
30
WuY.WeiC.LiX.LiY.QiuS.ShenW.et al (2018). In situ passivation of PbBr64– octahedra toward blue luminescent CsPbBr3 nanoplatelets with near 100% absolute quantum yield. ACS Energy Lett.3 (9), 2030–2037. 10.1021/acsenergylett.8b01025
31
XuH.LiuJ.WeiS.LuoJ.GongR.TianS.et al (2023). A multifunctional optoelectronic device based on 2D material with wide bandgap. Light Sci. and Appl.12 (1), 278. 10.1038/s41377-023-01327-8
32
YeJ.RenA.DaiL.BaikieT. K.GuoR.PalD.et al (2024). Direct linearly polarized electroluminescence from perovskite nanoplatelet superlattices. Nat. Photonics18 (6), 586–594. 10.1038/s41566-024-01398-y
Summary
Keywords
luminescent material, perovskite superlattices, linearly polarized light, transition dipole moment orientations, the degree of polarization
Citation
Yu S and Xu J (2025) Direct polarized luminescence from perovskite superlattices by manipulating transition dipole moment orientation. Front. Photonics 6:1637399. doi: 10.3389/fphot.2025.1637399
Received
29 May 2025
Accepted
24 June 2025
Published
04 July 2025
Volume
6 - 2025
Edited by
Sudhir Kumar, ETH Zürich, Switzerland
Reviewed by
Zhichao Zeng, Nankai University, China
Updates
Copyright
© 2025 Yu and Xu.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Jin Xu, xujin@fjirsm.ac.cn
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.