Chiral dicarbazole-ditriarylamine hole transport materials for circularly polarized electroluminescence

Abstract

Circularly polarized organic light-emitting diodes (CP-OLEDs) hold significant promise for 3D displays owing to their ability to directly emit circularly polarized light. However, achieving multicolor circularly polarized electroluminescence requires synthesizing and separating luminescence enantiomers with different emission wavelengths, greatly increasing manufacturing complexity and costs. In contrast, chiral hole transport materials present a straightforward and versatile strategy for achieving various high-performance CP-OLEDs. In this work, two pairs of chiral hole transport materials, R/S-CzTPA and R/S-BuCzTPA, were synthesized using R/S-1,1′-binaphthyl-2,2′-diamine as a chiral precursor. These compounds also integrate carbazole and triarylamine functional groups, combining efficient hole transport properties with axial chirality. The hole mobilities for R-CzTPA and R-BuCzTPA are measured as 5.63 × 10⁻⁵ and 2.72 × 10⁻⁶ cm² V⁻¹ s⁻¹ (E = 0.4 MV cm⁻¹), respectively. Additionally, these materials exhibit strong circularly polarized luminescence with dissymmetry factors (|g_lum|) of up to 5.7 × 10⁻³/2.5 × 10⁻³ in toluene and 3.6 × 10⁻³/1.9 × 10⁻³ in films, alongside excellent thermal stability. Notably, green CP-OLEDs are fabricated using R/S-CzTPA as the chiral hole transport layer and tris(2-phenylpyridine)iridium(III) as the achiral phosphorescent emitter, achieving the maximum luminance of 94 449/93 661 cd m⁻², the maximum current efficiency of 62/61 cd A⁻¹, the maximum external quantum efficiency of 19/18%, and an electroluminescence dissymmetry factor of −1.2 × 10⁻³/+1.6 × 10⁻³.

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Yuxia Zhang

Yuxia Zhang received her PhD degree from Nanjing University in 2022, under the supervision of Prof. Yixiang Cheng. She is currently a lecturer at the State Key Laboratory of Flexible Electronics (LoFE) & Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Nanjing University of Post & Telecommunications. Her research interests mainly focus on the design and synthesis chiral organic optoelectronic materials and their circularly polarized electroluminescence.

Introduction

Circularly polarized light has garnered extensive attention for its potential applications in future displays and photoelectric technology, such as optical spintronics and 3D displays.^1–7 Circularly polarized organic light-emitting diodes (CP-OLEDs) hold significant interest in 3D display technology, owing to their unique capability to directly generate circularly polarized light under electrical excitation (circularly polarized electroluminescence, CP-EL).^8–13 Generally, the polarization magnitude is quantified by the electroluminescence (EL) dissymmetry factor (g_EL), defined as 2(I_L − I_R)/(I_L + I_R), where I_L and I_R represent the intensities of the left- and right-handed CP-EL, respectively.^14,15 So far, the emitting layers, especially chiral luminescence materials, have attached considerable attention because of their intrinsically generating CP-EL, including chiral fluorescence,^16–19 chiral phosphorescence,^20–23 and chiral thermally activated delayed fluorescence (TADF) materials.^24–29 Nevertheless, achieving multicolor CP-EL necessitates the independent synthesis and the separation of enantiomers with distinct emission wavelengths, significantly escalating manufacturing complexity and production costs.

Recently, researchers have shifted their focus from chiral luminescence materials to other layers, such as chiral electron transport layers and chiral hole transport layers (HTLs).^30,31 In particular, chiral hole transport materials (HTMs) can function similarly to organic circularly polarizers in devices, resulting in the generation of CP-EL with less luminosity loss from achiral luminescence materials.³⁰ This is attributed to the emission of circularly polarized light from the emitter layers to the HTLs, and subsequently to the anode in bottom-emitting CP-OLEDs (Fig. 1a). In 2024, Zheng's group innovatively designed chiral hole transport enantiomers (R/S-NPACZ) using a one-pot synthesis method and reported the first example of CP-OLEDs based on chiral HTMs.³⁰ These CP-OLEDs, which utilized achiral multicolor phosphorescence and TADF materials as achiral emitters with varying wavelengths, exhibited obvious CP-EL signals, consistent with the generated EL spectra of the achiral emitters. These devices achieved external quantum efficiencies (EQEs) ranging from 14.1% to 30.7%, accompanied by |g_EL| values in the range of 8.8 × 10⁻⁴ to 3.6 × 10⁻³. Despite this progress, there remains a paucity of studies on chiral hole transport materials and their corresponding CP-OLEDs.

Fig. 1 (a) The CP-OLEDs based on the chiral hole transport layer; and (b) the chemical structures of R/S-CzTPA and R/S-BuCzTPA.

Axial chiral binaphthyl derivatives, modified with various functional groups at a well-defined molecular level, are well-known for their excellent circularly polarized luminescence (CPL) properties attributed to their stable chiral configurations.^32–36 Our group has recently conducted a series of investigations on chiral binaphthyl derivatives as chiral luminescence materials.^37,38 Herein, we synthesized two pair of carbazole (Cz) and triarylamine (TPA)-based chiral hole transport enantiomers, R/S-CzTPA and R/S-BuCzTPA, using R/S-1,1′-binaphthyl-2,2′-diamine as the chiral precursor (Fig. 1b). These enantiomers display obvious CPL signals, with g_lum values of up to ±5.7 × 10⁻³/±2.5 × 10⁻³ in toluene and ±3.6 × 10⁻³/±1.9 × 10⁻³ in films. The materials also exhibit efficient hole transport properties, with a hole mobility of 5.63 × 10⁻⁵ and 2.72 × 10⁻⁶ cm² V⁻¹ s⁻¹ (E = 0.4 MV cm⁻¹), respectively. Furthermore, green CP-OLEDs were fabricated using R/S-CzTPA as the chiral HTL and tris(2-phenylpyridine)iridium(III) as the achiral phosphorescent emitter. These devices achieved exceptional performance metrics: the maximum luminance of 94 449/93 661 cd m⁻², the maximum current efficiency of 62/61 cd A⁻¹, the maximum external quantum efficiency of 19/18%, and a g_EL value of −1.2 × 10⁻³/+1.6 × 10⁻³. This study broadens the range of chiral HTMs and further explores the impact of substituents on device efficiency and the g_EL value, thereby contributing to the achievement of high-performance CP-OLEDs.

Results and discussion

Synthesis and characterization

Two pairs of chiral HTMs, denoted as R/S-CzTPA and R/S-BuCzTPA, were synthesized through two step Buchwald–Hartwig coupling reactions as illustrated in Fig. 2a. All new compounds were characterized using ¹H NMR, ¹³C NMR and HRMS. As shown by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) curves in Fig. S1 (ESI†), the 5% weight loss degradation temperatures (T_d) for R-CzTPA and R-BuCzTPA are above 499.3 °C and 502.6 °C, respectively, while their glass transition temperatures (T_g) are recorded to be 190 °C and 233 °C. These results demonstrate their excellent thermal and morphological stabilities, which are essential characteristics for potential applications in OLEDs.

Fig. 2 (a) Chemical structures and synthesis process of R-CzTPA and R-BuCzTPA and (b) optimized structures and calculated HOMO–LUMO spatial distributions of R-CzTPA and R-BuCzTPA, calculated by the DFT method at the B3LYP/6-311G(d) level of theory in the gas phase.

Electrochemical properties and theoretical calculations

The electrochemical properties of R-CzTPA and R-BuCzTPA were performed by cyclic voltammetry (CV) in deoxygenated dichloromethane containing 0.1 M tetra-n-butylammonium hexafluorophosphate. As shown in Fig. S2 and Table S1 (ESI†), the onset oxidation potentials for R-CzTPA and R-BuCzTPA were determined to be 0.79 and 0.92 eV, respectively, corresponding to the highest occupied molecular orbital (HOMO) energy levels (E_HOMO) of −5.31 and −5.44 eV. The energy level gaps (E_g) for R-CzTPA and R-BuCzTPA were calculated to be 4.22 and 4.13 eV, respectively, based on their onset absorption wavelengths. The lowest unoccupied molecular orbital (LUMO) energy levels (E_LUMO) for R-CzTPA and R-BuCzTPA were derived as −1.09 and −1.31 eV, respectively, which were calculated from E_HOMO and optical E_g values.

To gain deeper insights into the electronic structures of R-CzTPA and R-BuCzTPA, density functional theory (DFT) calculations were conducted using the Gaussian 09 package at the B3LYP/6-311G(d) level. The optimized molecular structures and the HOMO–LUMO spatial distributions for both compounds are displayed in Fig. 2b. It is evident that the HOMO is primarily located in the Cz and TPA moiety, while the LUMO is predominantly distributed in the binaphthyl moiety. Additionally, a clear spatial separation between the frontier orbitals of R-BuCzTPA was observed, while R-CzTPA exhibits the overlaps between the HOMO and LUMO, indicating that the electrons on the molecular backbone can interact with each other. Notably, the HOMO of R-CzTPA is delocalized across all Cz and TPA units, unlike R-BuCzTPA, where it is localized on a single Cz and a single TPA unit. This difference stems from the electron-donating capacity of the tertiary butyl (^tBu) group. Consequently, R-CzTPA is expected to exhibit superior hole transport capability compared to R-BuCzTPA. Computational data indicate that the HOMO/LUMO energy levels of R-CzTPA and R-BuCzTPA are −5.28 eV/−1.56 eV and −5.15 eV/−1.52 eV, respectively, with band gaps (E_g) of 3.72 eV and 3.63 eV, aligning well with the CV data.

Photophysical and chiroptical properties

The UV-Vis absorption and fluorescence (FL) spectra of R-CzTPA and R-BuCzTPA in toluene (10⁻⁵ M) and films at 298 K are presented in Fig. 3a and Fig. S3a (ESI†), while the phosphorescence (PL) spectra in toluene (10⁻⁵ M) at 77 K are shown in Fig. S3b (ESI†). Both R-CzTPA and R-BuCzTPA exhibit two absorption bands at 225 and 300 nm attributed to the biphenyl group, and a broad shoulder peak at 310–400 nm, which is assigned to the absorption of Cz and TPA units. Their FL spectra display deep blue emission with a maximum wavelength of 428 nm. Moreover, at 77 K, two emission peaks appear at 515 nm and 546 nm with better resolved vibronic structures, due to the restrained molecular relaxation in the frozen media. This results in a calculated triplet energy level of 2.27 eV. Additionally, the excited-state lifetimes of R-CzTPA and R-BuCzTPA in films are 2.7 ns and 2.5 ns, respectively, suggesting fluorescence characteristics for both materials (Fig. S4 and Table S2, ESI†).

Fig. 3 (a) The UV-Vis absorption (straight line) and FL spectra (dashed line) of R/S-CzTPA and R/S-BuCzTPA in films at 298 K; and (b) CD spectra, (c) CPL spectra and (d) g_lumversus wavelength curves of R/S-CzTPA and R/S-BuCzTPA in films (λ_ex = 290 nm).

We further measured the circular dichroism (CD) and CPL spectra of R/S-CzTPA and R/S-BuCzTPA enantiomers in toluene and films, to study their chiroptical properties in the ground and excited states (Fig. 3b–d and Fig. S5, ESI†). Two pairs of chiral HTMs show mirror-image Cotton effects, with the |g_abs| values of 8.6 × 10⁻⁴/8.7 × 10⁻⁴ (237 nm), 1.1 × 10⁻³/1.2 × 10⁻³ (283 nm), 3.2 × 10⁻³/3.1 × 10⁻³ (326 nm), and 3.3 × 10⁻³/2.5 × 10⁻³ (374 nm) in films, respectively. As depicted in Fig. 3c, d, Fig. S5b, c and Table S2 (ESI†), both materials exhibit obvious mirror-image CPL signals, with |g_lum| values of approximately 5.7 × 10⁻³/2.5 × 10⁻³ (425 nm) in toluene and 3.6 × 10⁻³/1.9 × 10⁻³ (431 nm) in films, respectively.

Hole mobility measurements

The hole transport capability of an HTL critically influences the electroluminescence efficiency of devices. To evaluate this property, hole mobilities of R-CzTPA and R-BuCzTPA HTMs were measured using hole-only devices with the configuration: indium tin oxide (ITO)/MoO₃ (10 nm)/chiral HTMs (60 nm)/MoO₃ (10 nm)/Al (100 nm) (Fig. S6, ESI†). The hole current versus applied voltage plots (Fig. 4a) are analyzed via the single-carrier space-charge-limited current (SCLC) method in accordance with the Mott–Gurney law, expressed as J_SCLC = 9εε₀μ(V − V_bi)²/8L³. This equation is used to determine their hole mobilities, where ε (ε_CzTPA = 2.8, ε_BuCzTPA = 4.6) is the relative dielectric constant of the materials (Fig. S7 and S9, ESI†), ε₀ is the vacuum permittivity (taken as 8.85 × 10⁻¹² A² s⁴ kg⁻¹ m⁻³), μ is the hole mobility, V is the applied voltage across the device, V_bi is the built-in voltage (taken as zero), and L is the chiral HTM film thickness. The calculated hole mobilities for R-CzTPA and R-BuCzTPA are 5.63 × 10⁻⁵ cm² V⁻¹ s⁻¹ and 2.72 × 10⁻⁶ cm² V⁻¹ s⁻¹ (E = 0.4 MV cm⁻¹), respectively (Fig. 4b). The lower hole mobility of R-BuCzTPA likely arises from its HOMO being located on a single Cz and a single TPA unit, whereas R-CzTPA exhibits delocalization across all Cz and TPA units, facilitating more efficient hole mobility.

Fig. 4 (a) The current density–voltage (J–V) characteristics of the hole-only devices and (b) the hole mobilities of the hole-only devices under different electric fields.

Electroluminescence properties

Inspired by the good chiroptical properties in the film and suitable HOMO/LUMO energy levels of R/S-CzTPA and R/S-BuCzTPA, we investigated their application in CP-OLEDs as chiral HTMs (Fig. 5, Table 1 and Fig. S8, Table S3, ESI†). We selected the achiral phosphorescence complex tris(2-phenylpyridine)iridium(III) (Ir(ppy)₃) as the emitter and 4,4′-N,N-dicarbazole-biphenyl (CBP) as the host material within the emissive layer, displaying green emission.^39,40 Initially, the devices (R/S-A) were configured as ITO/MoO₃ (10 nm)/R/S-CzTPA (40 nm)/CBP:5% Ir(ppy)₃ (20 nm)/1,3,5-tri(mpyrid-3-yl-phenyl)-benzene (TmPyPB) (40 nm)/8-hydroxyquinolinolato-lithium (Liq) (2 nm)/Al (100 nm) (Fig. S9a, ESI†). As shown in Fig. 5a and Fig. S10 (ESI†), devices R/S-A with the single HTL exhibit stable green EL at 508 nm, with a turn-on voltage (V_on) of 4.5/4.0 V, a maximum luminance (L_max) of 42 859/34 816 cd m⁻², a maximum current efficiency (CE_max) of 16/17 cd A⁻¹, and a maximum external quantum efficiency (EQE_max) of 5/5%. Notably, devices R/S-A also displayed clear symmetric CP-EL signals with g_EL values of −0.89 × 10⁻³/+0.85 × 10⁻³ owing to the configurational stability of R/S-CzTPA enantiomers. This confirms that conventional electrophosphorescence can be converted into CP-EL via chiral HTMs. The reduction in g_EL values is primarily attributed to the partial racemization of the chiral hole transport materials under the high-temperature vapor deposition conditions (Fig. S11 and Table S4, ESI†).

Fig. 5 Device performance for R-A/B/C/D. (a) EL spectra; (b) current density–voltage–luminance (J–V–L) characteristics; (c) current efficiency–luminance curves; (d) external quantum efficiency–luminance curves; (e) CP-EL spectra; and (f) g_ELversus wavelength curves.

Table 1 CP-OLED data

Device	V on (V)	L max (cd m^−2)	λ EL (nm)	CEmax (cd A^−1)	EQEmax (%)	g EL (10^−3)
a Turn on voltage recorded at a brightness of 1 cd m^−2.
R-A	4.5	42 859	508	16	5	−0.89
R-B	3.0	94 449	508	62	19	−1.20
R-C	4.5	24 658	504	23	7	—
R-D	3.0	34 555	508	35	10	−0.57

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To improve device efficiency, devices R/S-B incorporated dual HTLs (R/S-CzTPA and 4,4′,4′′-tris(carbazol-9-yl)-triphenylamine (TCTA)) with the configuration ITO/MoO₃ (10 nm)/R/S-CzTPA (40 nm)/TCTA (10 nm)/CBP:5% Ir(ppy)₃ (20 nm)/TmPyPB (40 nm)/Liq (2 nm)/Al (100 nm) (Fig. S9b, ESI†). Specifically, devices R/S-B achieve enhanced performance metrics: V_on, L_max, CE_max, EQE_max and g_EL are 3.0/3.0 V, 94 449/93 661 cd m⁻², 62/61 cd A⁻¹, 19/18%, and −1.2 × 10⁻³/+1.6 × 10⁻³, respectively, as shown in the J–V–L curve and CP-EL spectra (Fig. 5 and Fig. S8, ESI†). These enhancements likely stem from optimized HOMO/LUMO energy alignment between the HTL and the emissive layer, alongside enhanced hole transport efficiency. Additionally, devices R/S-C, utilizing R/S-BuCzTPA as chiral HTMs, were fabricated with the configuration ITO/MoO₃ (10 nm)/R/S-BuCzTPA (40 nm)/TCTA (10 nm)/CBP:5% Ir(ppy)₃ (20 nm)/TmPyPB (40 nm)/Liq (2 nm)/Al (100 nm) (Fig. S9c, ESI†). Devices R/S-C display a lower L_max of 24 658/33 168 cd m⁻², CE_max of 23/23 cd A⁻¹, and EQE_max of 7/7% compared to devices R/S-B, which can be attributed to the lower hole mobility of R-BuCzTPA (Fig. 5 and Fig. S8, ESI†). In contrast, although R/S-BuCzTPA exhibit symmetric CPL signals, devices R/S-C revealed negligible CP-EL intensity (Fig. S12, ESI†). To evaluate the origin of CP-EL in CP-OLEDs, a 30 wt% achiral hole transport material (TCTA) doped in chiral HTMs was used as the HTL to disrupt the regular arrangement of R/S-CzTPA in the CP-OLEDs with Ir(ppy)₃ emitters. The configuration for devices R/S-D was defined as ITO/MoO₃ (10 nm)/R/S-CzTPA:30% TCTA (50 nm)/CBP:5% Ir(ppy)₃ (20 nm)/TmPyPB (40 nm)/Liq (2 nm)/Al (100 nm) (Fig. S9d, ESI†). As depicted in Fig. 5e, f and Fig. S8 (ESI†), R/S-D also exhibit symmetric CP-EL spectra with g_EL values of −0.57 × 10⁻³/+0.54 × 10⁻³, which are close to those of R/S-A (−0.89 × 10⁻³/+0.85 × 10⁻³). Therefore, it can be concluded that the CP-EL is derived from the chiral conformation of the HTM enantiomers rather than anisotropic molecular packing.³⁰

To further elucidate the chirality transfer mechanism of CP-OLEDs based on chiral HTLs, a double-sided light emitting device E with a thinner Al layer was designed and fabricated with the following structure: ITO/MoO₃ (10 nm)/S-CzTPA (40 nm)/TCTA (10 nm)/CBP:5% Ir(ppy)₃ (20 nm)/TmPyPB (40 nm)/Liq (2 nm)/Al (5 nm) (Fig. S13a, ESI†). Under excitation with 290 nm UV light, an obvious CPL signal from Ir(ppy)₃ was detected from the Al side (Fig. S14, ESI†). This indicates that the unpolarized emission of Ir(ppy)₃ can be changed into CP light through passing the chiral HTL. In addition, device F with an achiral HTL (N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine, NPB) was prepared, while a chiral S-CzTPA layer was subsequently deposited on the glass substrate in the direction of light emission (Fig. S13b, ESI†). As shown in Fig. S15 (ESI†), an obvious CP-EL signal was observed at 510 nm, indicating that the chiral S-CzTPA layer can function similarly to organic circular polarizers in devices.

Conclusions

In summary, two pairs of axial chiral HTMs, R/S-CzTPA and R/S-BuCzTPA, were designed and synthesized from R/S-1,1′-binaphthyl-2,2′-diamine and 9-phenylcarbazole, combining efficient hole transport properties with axial chirality. Both enantiomers demonstrate obvious CPL signals with g_lum values of up to ±3.6 × 10⁻³/±1.9 × 10⁻³ in films and a superior hole mobility of 5.63 × 10⁻⁵ cm² V⁻¹ s⁻¹ and 2.72 × 10⁻⁶ cm² V⁻¹ s⁻¹ (E = 0.4 MV cm⁻¹), respectively. The difference in hole mobility is ascribed to the electron-donating effect of the tertiary butyl substituent in R/S-BuCzTPA, which influences the HOMO distribution on Cz and TPA units. Notably, green CP-OLEDs incorporating dual HTLs were fabricated with the configuration ITO/MoO₃ (10 nm)/R/S-CzTPA (40 nm)/TCTA (10 nm)/CBP:5% Ir(ppy)₃ (20 nm)/TmPyPB (40 nm)/Liq (2 nm)/Al (100 nm), exhibiting exceptional performance metrics: V_on, L_max, CE_max, EQE_max and g_EL were 3.0/3.0 V, 94 449/93 661 cd m⁻², 62/61 cd A⁻¹, 19/18%, and −1.2 × 10⁻³/+1.6 × 10⁻³, respectively. Additionally, studies on the chirality transfer mechanism have revealed that the CP-EL in chiral HTL-based devices stems from organic circular polarizers. This work provides an effective strategy for developing high-performance chiral HTMs.

Author contributions

Y. Wang contributed to synthesis, measurements, and data analysis. J. Xu was responsible for the fabrication of CP-OLEDs. X. Wang conducted electroluminescence measurements. Y. Zhang and Y. Wang collaboratively wrote the manuscript. S. Liu contributed to data analysis. Y. Zhang conceived the idea for this study. X. Zhang, Y. Ma, and Q. Zhao revised the manuscript and provided valuable suggestions. All authors discussed the results and commented on the manuscript at all stages.

Data availability

The data supporting this article have been included as part of the ESI.†

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

We gratefully acknowledge financial support from the National Key Research and Development Program of China (2022YFA1204404), the National Natural Science Foundation of China (62305172 and 62288102), the Natural Science Fund for Colleges and Universities in Jiangsu Province (23KJB430026), the National Key Research and Development Program of China (2024YFB3612500), and the Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications (NY223052). This study was supported by the Project of State Key Laboratory of Flexible Electronics (LoFE), Nanjing University of Posts and Telecommunications.

References

1. N. P. M. Huck, W. F. Jager, B. D. Lange and B. L. Feringa, Science, 1996, 273, 1686–1688.
2. J. F. Sherson, H. Krauter, R. K. Olsson, B. Julsgarrd, K. Hammerer, I. Cirac and E. S. Polzik, Nature, 2006, 443, 557–560.
3. L. E. MacKenzie and R. Pal, Nat. Rev. Chem., 2021, 5, 109–124.
4. G. Zhan, J. Zhang, L. Zhang, Z. Ou, H. Yang, Y. Qian, X. Zhang, Z. Xing, L. Zhang, C. Li, J. Zhong, J. Yuan, Y. Cao, D. Zhou, X. Chen, H. Ma, X. Song, C. Zha, X. Huang, J. Wang, T. Wang, W. Huang and L. Wang, Nano Lett., 2022, 22, 3961–3968.
5. M. Zhang, Q. Guo, Z. Li, Y. Zhou, S. Zhao, Z. Tong, Y. Wang, G. Li, S. Jin, M. Zhu, T. Zhuang and S. Yu, Sci. Adv., 2023, 9, eadi9944.
6. L. Yuan, Y. Zhang and Y. Zheng, Sci. China: Chem., 2024, 67, 1097–1116.
7. S. Wang, B. An, R. Ma, Z. Yi, W. Li, Y. Liu and Y. Zhao, Adv. Funct. Mater., 2025, 2416920.
8. E. Peeters, M. P. T. Christiaans, R. A. J. Janssen, H. F. M. Schoo, H. P. J. M. Dekkers and E. W. Meijer, J. Am. Chem. Soc., 1997, 119, 9909–9910.
9. M. Oda, H. G. Nothofer, G. Lieser, U. Scherf, S. C. J. Meskers and D. Neher, Adv. Mater., 2000, 12, 362–365,  DOI:10.1002/(SICI)1521-4095(200003)12:5<362::AID-ADMA362>3.0.CO;2-P.
10. D. Zhang, M. Li and C. Chen, Chem. Soc. Rev., 2020, 49, 1331–1343.
11. L. Frédéric, A. Desmarchelier, L. Favereau and G. Pieters, Adv. Funct. Mater., 2021, 31, 2010281.
12. Y. Zhang, S. Song, M. Mao, C. Li, Y. Zheng and J. Zuo, Sci. China: Chem., 2022, 65, 1347–1355.
13. P. Fan, L. Hua, X. Lai, H. Ni, W. Zhu, Y. Zheng and Y. Wang, Adv. Funct. Mater., 2024, 2418790.
14. Y. Geng, A. Trajkovska, S. W. Culligan, J. J. Ou, H. M. P. Chen, D. Katsis and S. H. Chen, J. Am. Chem. Soc., 2003, 125, 14032–14038.
15. Y. Yang, R. C. da Costa, D. M. Smilgies, A. J. Campbell and M. Fuchter, Adv. Mater., 2013, 25, 2624–2628.
16. X. Lai, Q. Zhong, C. Xiao, S. Cowling, P. Duan, D. Bruce, W. Zhu and Y. Wang, Chem. Commun., 2024, 60, 2026–2029.
17. Z. Geng, Z. Liu, H. Li, Y. Zhang, W. Zheng, Y. Quan and Y. Cheng, Adv. Mater., 2023, 35, 2209495.
18. D. Li, Z. Jiang, S. Zheng, C. Fu, P. Wang and Y. Cheng, J. Colloid Interface Sci., 2025, 678, 1213–1222.
19. F. Zinna, C. Botta, S. Luzzati, L. Bari and U. Giovanella, Adv. Funct. Mater., 2025, 2423077.
20. G. Qian, X. Yang, X. Wang, J. Herod, D. Bruce, S. Wang, W. Zhu, P. Duan and Y. Wang, Adv. Opt. Mater., 2020, 8, 2000775.
21. G. Zou, Z. Jiang, D. Li, Q. Lia and Y. Cheng, Chem. Sci., 2024, 15, 18534–18542.
22. Z. Huo, Y. Wang, B. Yang, J. Liang, X. Hong, Q. An, L. Yuan, H. Ma, J. Zuo and Y. Zheng, Adv. Opt. Mater., 2024, 2402684.
23. S. Suzuki, Y. Yamamoto, M. Kitahara, R. Shikura, S. Yagi and Y. Imai, J. Mater. Chem. C, 2024, 12, 3430–3436.
24. M. Li, S. Li, D. Zhang, M. Cai, L. Duan, M. Fung and C. Chen, Angew. Chem., Int. Ed., 2018, 57, 2889–2893.
25. Y. Zhang, X. Liang, X. Luo, S. Song, S. Li, Y. Wang, Z. Mao, W. Xu, Y. Zheng, J. Zuo and Y. Pan, Angew. Chem., Int. Ed., 2021, 60, 8435–8440.
26. S. Yang, Z. Feng, Z. Fu, K. Zhang, S. Chen, Y. Yu, B. Zou, K. Wang, L. Liao and Z. Jiang, Angew. Chem., Int. Ed., 2022, 61, e202206861.
27. Y. Xu, H. Hafeez, J. Seibert, S. Wu, J. Ortiz, J. Crassous, S. Bräse, I. Samuel and E. Colman, Adv. Funct. Mater., 2024, 34, 2402036.
28. C. Feng, K. Zhang, B. Zhang, L. Feng, L. He, C. Chen and M. Li, Angew. Chem., Int. Ed., 2025, e202425094.
29. M. Gong, L. Yuan, Y. X. Zheng and W. H. Zheng, Adv. Funct. Mater., 2024, 34, 2314205.
30. X. Zhong, L. Yuan, X. Liao, J. Hu, S. Xing, S. Song, J. Xi and Y. Zheng, Adv. Mater., 2024, 36, 2311857.
31. P. Huo, T. Yang, P. Fang, Y. Li, N. Zheng, M. Gong, Z. Bian and Z. Liu, Sci. China: Chem., 2024, 67, 3777–3784.
32. Y. Zhang, Y. Li, Y. Quan, S. Ye and Y. Cheng, Angew. Chem., Int. Ed., 2023, 62, e202214424.
33. Y. Yan, Z. Cheng, Y. Xu, Z. Su, Y. Wang, X. He, Z. Zhao, F. Liu and P. Lu, Adv. Funct. Mater., 2024, 34, 2408550.
34. K. Wang, X. Ou, X. Niu, Z. Wang, F. Song, X. Dong, W. Guo, H. Peng, Z. Zhao, J. Lam, J. Sun, H. Wu, S. Yu, F. Li and B. Tang, Aggregate, 2025, 6, e667.
35. L. Li, P. Jiang, X. Zhang and Y. Li, Angew. Chem., Int. Ed., 2025, 64, e202417149.
36. Y. Zhang, H. Li, Z. Geng, W. Zheng, Y. Quan and Y. Cheng, Nat. Commun., 2022, 13, 4905.
37. Y. Zhang, H. Li, Z. Geng, W. Zheng, Y. Quan and Y. Cheng, ACS Nano, 2022, 16, 3173–3181.
38. P. She, Y. Qin, Y. Zhou, X. Zheng, F. Li, S. Liu, Y. Ma, Q. Zhao and W. Wong, Angew. Chem., Int. Ed., 2024, 63, e202403660.
39. W. Nie, J. Jiang, Z. Zhao, D. Song, B. Qiao, Z. Xu and S. Zhao, Synth. Met., 2023, 297, 117426.
40. S. Lin, Y. Cheng, C. Chen, Y. Zhang, J. Lee, M. Leung, B. Lin and T. Chiu, J. Mater. Chem. C, 2023, 11, 161–171.

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Footnotes

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d5tc01025j

‡ These authors contributed equally.

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