Research Advances in Helicene Structure-Based Chiral Luminescent Materials and Their Circularly Polarized Electroluminescence

Xu-Feng Luo Jie He Yang Wang Dai Hong Zheng-Guang Wu

Citation:  Xu-Feng Luo, Jie He, Yang Wang, Dai Hong, Zheng-Guang Wu. Research Advances in Helicene Structure-Based Chiral Luminescent Materials and Their Circularly Polarized Electroluminescence[J]. Chinese Journal of Structural Chemistry, 2022, 41(12): 221207. doi: 10.14102/j.cnki.0254-5861.2022-0196 shu

Research Advances in Helicene Structure-Based Chiral Luminescent Materials and Their Circularly Polarized Electroluminescence

    作者简介: Xu-Feng Luo received his Ph.D. degree in 2022 at Nanjing University under the supervisor of Professor You-Xuan Zheng from 2017 to 2022. Now he joined the Ningbo University of Technology. His research focuses on MR-TADF materials, phosphorescence metal complexes and CPL materials and their applications in optoelectronic device;
    Jie He received his B.S. degree at the Nantong University in 2019. He is currently an M.S. candidate in the School of Chemistry and Chemical Engineering, Nantong University, supervised by Prof;
    Yang Wang obtained his B.S. and M.S. degree in chemistry from Jiangsu Normal University under the supervisor of Prof. Feng Shi in 2016. Then, he joined professor Wen-Hua Zheng's group and received his Ph.D. from Nanjing University in 2019. He is currently a lecturer at the School of Chemistry and Chemical Engineering, Nantong University, where his research focuses on the construction of chiral nitrogen heterocycles via asymmetric oxidative strategies;
    Hong Dai received his PhD degree from Nankai University under the supervision of Prof. Jianxin Fang in 2009. He joined Nantong University in 2009, and was promoted as Professor in 2018. Currently, his research is focused on the design and synthesis of chiral heterocycles for pesticide molecules and photoelectric materials;
    Zheng-Guang Wu, Professor, received his Ph.D. degree in Organic Chemistry in 2017 at Nanjing University under the supervisor of Prof. Yi Pan and You-Xuan Zheng. From 2017 to 2019, he worked as a postdoctoral fellow in State Key Laboratory of Coordination Chemistry in Nanjing University. He joined Nantong University in 2020 and his research interest focuses on the design and synthesis of inorganic and organic functional materials, chiral luminescent materials and their applications in optoelectronic device;

English

  • Circularly polarized luminescence (CPL) displays potential applications in optical information storage, quantum communication, bioimaging, liquid crystal displays, and backlights in 3D displays.[1-5] Generally, CP light can be obtained from non-polarized light continuously utilizing a linear polarizer and quarter-wave plate, however, this method suffers from efficiency and brightness loss with complicated device architecture (Figure 1a). Apart from this physical approach, CP light could also be directly obtained from chiral luminescent materials, which are featured of optical rotation characteristics and circular dichroism (CD) enabling to directly emit right- and left-CP light.[6-17] Due to the different intrinsic excitation mechanisms, CP light can be classified into CP photoluminescence (CPPL) and CPEL. So far, although significant improvements have been made in terms of CPPL research, the development of CPEL with more application prospects in optoelectronic technology still lags behind.[5, 18-22] Therefore, it is of urgency to develop efficient chiral emitters and devices with excellent CPEL properties to meet practical application.

    Figure 1

    Figure 1.  (a) The schematic diagram of the physical method versus (b) CP-OLEDs for obtaining CP light.

    Since the first investigation to obtain direct CP light from organic electroluminescent displays by Meijer et al. in 1997, [23] tremendous efforts have been devoted to develop chiral emitters-based OLEDs. CP-OLEDs, which are favorable for generating CP light directly, in terms of facile device architectures, tunable emission colors and high efficiencies, have become a significant and prospective research field (Figure 1b).[5] Device performance and CPEL activity are the key to determine CP-OLEDs performances. Similar to traditional OLEDs, the performance evaluation of CP-OLEDs mainly starts from low turn-on voltage, high brightness, high efficiency with low roll-off, and long device lifetime. While the chiroptical performances of CP-OLEDs are mainly evaluated by the asymmetry factor (g) value, which is measured by a CPL spectrometer and defined by formula (1).

    $ g = 2(I _{\rm{L}} - I _{\rm{R}})/(I _{{\rm{L}}} + I _{{\rm{R}}}) $

    (1)

    where IL and IR denote the intensities of left- and right-handed CP component of the emitting light, respectively. A g value of zero indicates that the emitting light has no circular polarization, and +2 or -2 shows completely left- or right-handed CP light, respectively. According to the different excitation mechanisms, gPL represents the CPPL intensity of the chiral luminescent materials from photo excitation while gEL indicates the CPEL activity of chiral luminescent materials-based CP-OLEDs from electric excitation. Therefore, it is urgent and significant to develop CP-OLEDs based on chiral emitters with both high device performances and large gEL values of CPEL.

    The core of CP-OLEDs is the chiral luminescent material, which is responsible for generating CPEL. In general, chiral emitters from three categories are used in fabricating CP-OLEDs, including chiral conjugated polymers, chiral metal complexes (Eu, Ir, Pt, Zn, et al.), chiral simple organic molecules (SOMs), especially thermally activated delayed fluorescence (TADF) materials[24-30] which are regarded as promising for their high-performance CP-OLEDs with producing metal-free and low-cost. Alternatively, based on different chirality sources, chiral luminescent materials with CPL properties are classified into four types of central chirality, axial chirality, planar chirality, and helical chirality (Figure 2).[31-40] Notably, helicene derivatives featured of helical structures are a type of aromatic ortho-fused polycyclic compounds. Due to terminal aromatic rings' spatial hindrance, helicene molecular skeletons can be distorted for forming a spiral structure. Although such molecules do not have any asymmetric carbon centers, their twisted non-planar skeleton and extended π-conjugated molecular structures endow them with the characteristic of special helical chirality and exhibit excellent CPL properties, [41-47] which has been employed as the ingenious chirality core for constructing efficient chiral luminescent materials. Although significant improvements have been made in the research of CPPL from helicene compounds, it is still a big gap in the practical application of optoelectronic technology.

    Figure 2

    Figure 2.  Categories of chiral luminescent materials.

    In this review, we concisely discuss the recent advance, current challenge and outlook of helicene structure-based chiral luminescent materials and their CP-OLEDs with circularly polarized electroluminescence performances, which will not only be helpful for developing CPL/CPEL materials but also be beneficial for investigating optoelectronic devices.

    Helicene Structure-Based Chiral Fluorescence Molecules. The first attempt to obtain CP light from helicene-based OLEDs was made by Fuchter laboratory in 2013.[48] A pair of chiral SOMs (M) or (P)-1-Aza[6] helicene was successfully doped in a conventional achiral light-emitting polymer (LEP) F8BT to directly generate high levels of CPL activity (Figure 3a). A small amount of enantiopure 1-Aza[6] helicene (7 wt%) was doped into LEP, leading to a big CPPL signal of the F8BT film with the gPL over 0.2. With the increase of 1-Aza[6] helicene blending ratio, the gPL factor was improved to a significantly high value of 0.5 for the 53% helicene blend (Figure 3b). Notably, the CP-OLED was successfully fabricated by using F8BT: enantiopure 1-Aza[6] helicene (7% wt) as the emitter to directly emit CPEL with brightness up to 3000 cd/m2 and power efficiency of 1.1 lm/W with a gEL value of 0.27 (Figure 3c). This work successfully demonstrated an effective strategy to directly generate efficient CPEL based on doping a conventional achiral polymer with a chiral helicene emitter. After that, the blend ratio, film thickness, device architecture, material category, and so on were also systematically investigated by Fuchter group for achieving both good efficiency and large gEL value of CP-OLEDs.[49-51]

    Figure 3

    Figure 3.  Molecular structures of (M/P)-1-Aza[6] helicene and light-emitting polymer F8BT. (b) CPPL spectra of F8BT doped with (+)-1-Aza[6] helicene. (c) CPEL spectra.[48] Copyright 2013, WILEY-VCH.

    Li et al. designed and synthesized a pair of helicene enantiomers, (P)-HAI and (M)-HAI (Figure 4a).[52] The helicene enantiomers with the rigid helical π-skeleton showed excellent photophysical properties, especially intense mirror-image CPL activities with large gPL value of about 6×10-3. Importantly, the CP-OLEDs with helicene enantiomers as emitters and a TADF molecule as sensitizer not only exhibited better performance of lower turn-on voltage of 2.6 V, four-fold maximum external quantum efficiency (EQEmax) of 5.3%, and lower efficiency roll-off than the devices without TADF sensitizer, but also exhibited intense CPEL signals with gEL values of -2.3×10-3 and +3.0×10-3 (Figure 4b). This research leads to the development of thermally activated sensitized fluorescent CP-OLEDs with markedly enhanced efficiencies and intense CPEL.

    Figure 4

    Figure 4.  Molecular structures of the helicene enantiomers (P)-HAI and (M)-HAI. (b) CPEL spectra and gEL versus wavelength curves of the CP-OLEDs.[52] Copyright 2020, Science China Press.

    Dhbaibi et al. developed novel twisted helical push-pull chiral emitters (Figure 5a), [53] which show strong CD and CPL activities with gPL values up to 3×10-2, among the highest CPL intensities at the molecular level reported so far. Due to their strong CPL and high racemization barrier, these chiral derivatives were then doped in proof of concept top-emission CP-OLEDs and afforded a promising CPEL signal with the gEL of around 8×10-3 (Figure 5b), which represents a significant result for CP-OLEDs using top-emission device architecture.

    Figure 5

    Figure 5.  (a) Molecular structures and g values for each compound. (b) gPL and gEL based on (P) or (M)-H6(TMS)2.[53] Copyright 2021, Royal Society of Chemistry.

    Though the CP-OLEDs with helicene structure-based chiral fluorescence molecules illustrated relatively large gEL value, the EL efficiency is low due to the only 25% utilization of excitons. Notably, a novel strategy for TADF-sensitized helicene enantiomer-based OLEDs opens up a novel research direction towards achieving efficient CP-OLEDs with improved EL efficiency and large g value.

    Helicene Structure-Based Transition Metal Complexes. As fluorescent material can only use singlet luminescence, its maximum internal quantum efficiency is only 25%. Phosphorescent materials, such as iridium and platinum complexes, can introduce heavy metal atoms to the spin-orbit coupling, leading to the quantum efficiency of 100%. Though helicene compounds have larger g value and the transition phosphorescent metal complexes own sufficient photoluminescence quantum efficiency (PLQY), the research on helicene structure-based chiral metal complexes, especially their CP-OLEDs, is rare due to the difficulties in their synthesis and device fabrication.

    Crassous group developed an iridium complex A2 with fused π-helical N-heterocyclic carbene (NHC) structure (Figure 6).[54] The enantiomers exhibit green emission with unusually long lifetimes and circular polarization with gPL value around 10-3. This novel diversification in organometallic helicene chemistry endows molecules with distinctive features and opens a new field, namely Ir-NHC-helicene complexes. However, there is no research on CPEL from these Ir-NHC-helicene complexes.

    Figure 6

    Figure 6.  Molecular structure of the helicene iridium complex A2.

    Fuchter group developed a pair of platinahelicene complexes (+/-)-1[55] to construct a solution-processed circularly polarized phosphorescent organic light-emitting diode (CP-PhOLED) that achieves a very high gEL value of up to 0.38, which is the best result among the platinum complexes-based CP-OLEDs. Unfortunately, the device performances of current efficiency of 0.25 cd/A and maximum luminance of 222 cd/m2 are insufficient for practical application (Figure 7). Notably, the dissymmetry of CP emission from this helicene-based device efficiently provides real-world advantages compared to nonpolarized emission, and will pave the way to chiral metal complex-based CP-PhOLED displays.

    Figure 7

    Figure 7.  (a) Molecular structure of platinahelicene complex (+/-)-1. (b) gEL as a function of emission wavelength.[55] Copyright 2016, American Chemical Society.

    Zheng group designed and synthesized a pair of platinahelicene enantiomers (M)-Pt and (P)-Pt (Figure 8a) by decorating the pyridinyl-helicene ligands with -CF3 and -F groups, [56] which are featured of superior configurational stability, high sublimation yield (> 90%) and obvious CPPL properties with gPL of approximately 3.7×10-3 in solution and about 4.1×10-3 in doped film. Notably, the evaporated CP-PhOLEDs with enantiomers as emitters exhibited symmetric CPEL signals with gEL value of 1.1-1.6×10-3 (Figure 8b) and decent device performances with a maximum brightness of 11590 cd/m2 and an EQEmax up to 18.81%, which are the best results among the reported devices from chiral phosphorescent Pt(Ⅱ) complexes. To suppress the effect of reverse CPEL signal from the cathode reflection, the further fabrication of semitransparent aluminum/ silver cathode-based CP-OLED successfully boosts up the gEL by over three times to 5.1×10-3 (Figure 8c).

    Figure 8

    Figure 8.  (a) Molecular structures of platinahelicene enantiomers (M)-Pt and (P)-Pt. (b) CPEL spectra and gEL versus wavelength curves. (c) CPEL spectra and gEL versus the wavelength curves of semitransparent electrode devices.[56] Copyright 2019, WILEY-VCH.

    By regulating the position of CF3 group, another pair of platinahelicene enantiomers with deep red emission was also developed by Zheng group (Figure 9a).[57] Compared with the platina helicene reported by Crassous and Fuchter, (M/P)-Pt displays excellent thermal stability and could be easily sublimated because of the introduction of peripheral hindered groups (CF3, tBu). Additionally, the special substitution position of the groups not only endows the helicene structure with more configurationally stable, but also enables (M/P)-Pt better CPL performance with gPL value of 6×10-3 due to the more twisted structures. The platinahelicene enantiomers-based evaporated CP-OLEDs displayed the deep-red emission with the peak at 653 nm and obvious CPEL signals with the gEL in 10-3 order (Figure 9b). Therefore, the design strategy affords an efficient way to enhance the CPL performances of platinahelicene to realize the future application in CP-OLEDs.

    Figure 9

    Figure 9.  (a) Molecular structures of (M/P)-Pt. (b) CPEL spectra and gEL versus wavelength curves.[57] Copyright 2020, Yan, Luo, Liao, Zheng and Zuo.

    Yuan et al. synthesized three pairs of tetradentate Pt(Ⅱ) enantiomers[58] with a helical structure by adjusting a six-membered to a five-membered metallocycle and replacing quinoline by benzo[h]quinoline with greater steric hindrance, and the configurational stability of the Pt(Ⅱ) complex is gradually improved (Figure 10a). Compared with Pt1 enantiomer with fused 6/6/6 metallocycles, which is easy to racemize at room temperature, the Pt2 enantiomer with 5/6/6 metallocycles shows phosphorescent CPL properties with gPL of +6.77/-5.22×10-3 in CH2Cl2 solutions at room temperature. By using a benzo[h]quinoline group to replace a quinoline unit, the larger overlap between the second quinoline and benzo[h]quinoline leads to good configurational stability of Pt3 enantiomers at evaporation temperature. The evaporated OLEDs with Pt1 and Pt2 emitters show good device performances with an EQEmax of 14.2% and a maximum luminance of 39072 cd/m2. Based on the good configurational stability of Pt3 enantiomers, the evaporated CP-OLEDs with Pt3 enantiomers show symmetrical CPEL signals with gEL value of +6.81/ -6.49×10-4, as well as an EQEmax of 12.6% (Figure 10b).

    Figure 10

    Figure 10.  (a) Molecular structures of the chiral Pt(Ⅱ) complexes. (b) CPEL spectra and gEL versus wavelength curves.[58] Copyright 2021, Royal Society of Chemistry.

    The author also synthesized a pair of helicene Pt(Ⅱ) enantiomers, (RR)-P-QPt and (SS)-M-QPt.[59] The intrinsic P- and M-configurations were effectively induced from intrinsic chiral carbon centers (R or S), ingeniously avoiding the racemic mixture formation and chiral separation (Figure 11a). Notably, the chirality originating from both chiral carbon centers and helicene-like structure enhances the g factor greatly (Figure 11b). Though no CPEL was reported, this study brings new inspiration for the design of chiral Pt(Ⅱ) enantiomers with good CPL properties.

    Figure 11

    Figure 11.  (a) Design strategy and molecular structures of chiral tetradentate Pt(Ⅱ) complexes. (b) CPPL spectra and gPL versus wavelength curves.[59] Copyright 2022, Elsevier.

    The research on CP-OLEDs based on helicene phosphorescent metal complexes is scarce, and high g factors and satisfactory device performances seem to be incompatible currently.

    Helicene Structure-Based TADF Molecules. Merging CPL functions into TADF structures is an effective strategy for directly constructing circularly polarized thermally activated delayed fluorescence (CP-TADF) materials. The high quantum efficiency and nearly 100% exciton utilization of CP-TADF molecules could effectively overcome the inherent shortcomings of traditional chiral fluorescent molecules and chiral lanthanide complexes, while helicenes often show strong chiral optical performance due to their inherent spiral chirality and π-conjugate electronic structures. Combining the superiority of these two molecules, the design and development of helicene structure-based TADF chiral molecule will promote the overlap of luminescence center and chiral core, thus achieving the organic unity of high efficiency and large g factor for realizing highly efficient CP-OLEDs.

    Integrated CP-TADF and MR-TADF (CPMR-TADF) molecules are constructed from Zhu group by strategic design and synthesis of asymmetrical peripherally locked enantiomers, which are separated and named as (+/-)-BN4 and (+/-)-BN5 with TADF and CPL properties (Figure 12a).[60] Because of the entire molecular frame coverage in the frontier orbitals, (+)/(-)-BN4- and (+)/(-)-BN5-based solution processed organic light-emitting diodes (OLEDs) achieved narrow full width at half maximum (FWHMs) of 49/49 and 48/48 nm and a high EQEmax of 20.6%/19.0% and 22.0%/ 26.5%, respectively. Importantly, unambiguous CPEL signals with gEL values of +3.7/-3.1×10-3 (BN4) and +1.9/-1.6×10-3 (BN5) are obtained (Figure 12b). This research provides a facile and general concept for developing CPMR-TADF materials simultaneously with high efficiency, high color purity, and large luminescence dissymmetry factor, promoting the CP-TADF materials for practical applications in optoelectronics.

    Figure 12

    Figure 12.  (a) Molecular structures of B/N nanographenes. (b) gEL versus wavelength curves.[60] Copyright 2021, WILEY-VCH.

    Yang group reported a helical M-shaped double hetero [5]helicene, [61] (P/M)-helicene-BN, featured of the B/N/S embedded polycyclic fused aromatic skeleton, which was conveniently synthesized by a two-step method. These enantiomers-based CP-OLEDs achieved very high EQEmax over 30% and high brightness over 70, 000 cd/m2, as well as pure-green emission with a narrow FWHM of 49 nm. Importantly, the CP-OLED based on helicene-BN enantiomer exhibited strong CPEL signals with gEL value up to 2.2×10-3 (Figure 13).

    Figure 13

    Figure 13.  Molecular structure of (P/M)-helicene-BN and gEL values versus wavelength curves of (P/M)-helicene-BN based CP-OLEDs.[61] Copyright 2022, Chinese Chemical Society.

    A novel strategy for designing narrowband CP-TADF emitters with a triarylamine-based helicene framework was proposed by Jiang group. This design adopts carbonyl/nitrogen (C=O/N) or (C=O/N/O=S=O) system[62, 63] as a MR-TADF framework and introduces 9-phenyl-9H-carbazole (PhCz) at the ortho position of the central nitrogen to construct a helical structure, illustrating the origin of molecular chirality (Figure 14a). (M)-QAO-PhCz or (P)-QAO-PhCz presents CPL activity with gPL as high as 1.1×10-3 in toluene. The offered OLEDs utilizing QAO-PhCz as guest show blue electroluminescence (467 nm) with a narrow FWHM of 36 nm and an EQEmax of 14.0%. Finally, the CP-OLEDs display distinct CPEL signal with gEL of 1.5×10-3 for (P)-QAO-PhCz (Figure 14b). Due to the similar helicene structure, the performances of QPO-PhCz enantiomers can match that of QAO-PhCz, with gPL of 1.2×10-3 in solution, EQEmax of 10.6%, gEL of +1.6×10-3 and 1.1×10-3 for (M)-QPO-PhCz and (P)-QPO-PhCz, respectively (Figure 14c). These results demonstrate a new route to develop efficient CPL/CPEL materials from heterohelical structures and may enlighten related optoelectronic areas.

    Figure 14

    Figure 14.  (a) Molecular structures. (b) and (c) gEL versus wavelength curves.[62, 63] Copyright 2021, Royal Society of Chemistry.

    Using helicene structure-based TADF molecules for CP-OLED is an effective strategy for achieving high EL efficiency, however, the CPEL intensity and gEL value are hardly satisfactory at present. The development of efficient helicene TADF materials for practical CP-OLEDs merging high efficiency and intense CPEL is urgent.

    This review systematically summarizes the latest progress on helicene structure-based chiral luminescent materials and their circularly polarized electroluminescence performances of CP-OLEDs. Generally, the CP-OLEDs fabricated with helicene fluorescence molecules show large gEL value, but poor device performances due to the 25% utilization of excitions. While helicene phosphorescent metal complexes usually exhibit decent EL efficiency with EQE over 18%, but the gEL value is low at the 10-3 level, except for platinum complex (+/-)-1-based solution process devices with gEL of up to 0.38. As for helicene structure-based TADF materials, excellent photophysical properties made them become promising materials for producing metal-free, low-cost, and high-performance CP-OLEDs. Although the EL efficiency of CP-OLEDs is fascinating with EQE over 30%, the low gEL is difficult for practical applications at present.

    The systematic studies on helicene chiral materials for CPEL are relatively few, which is in its infancy, but the present results offer the direction and hope for developing efficient helicene structure-based chiral luminescent materials for fabricating CP-OLEDs. Achieving large gEL values and high efficiency simultaneously through technical means such as new molecular structure design and ingenious device fabrication technique of CP-OLEDs based on helicene chiral emitters remains a huge challenge.

    At the molecule level, the development of new chiral emitters with both high PLQYs and large gPL values will always be the primary goal of this research area, especially for designing novel helicene phosphorescent metal complexes and TADF molecules, which are of great significance because high PLQY and nearly 100% utilization of excitons are important for the high efficiency of device. As CPEL performance mainly depends on emissive layers rather than single molecules, the formation of supramolecular spiral structure through annealing or affixing of the external layer becomes effective means to greatly amplify the g factor for meeting the industrial requirements. Besides, the properties of other materials such as hole injection material (HIM), hole transport material (HTM), host and electron transport material (ETM) in OLEDs may also influence the CPEL activity and gEL. The CP-OLEDs with the architecture of full chiral layers (FCLs) with chiral ETM, chiral host: chiral emitter, chiral HTM and chiral HIM materials may improve the gEL value due to the amplification and superposition of CPEL signals (Figure 15a). Furthermore, as we know, gEL values are usually lower than the gPL ones, which may be attributed to light reflection in the OLED stack, such as cathode reflection of aluminum, thus leading to depolarization and consumption of CPEL intensity. Through suitable device engineering, we believe that semi- or fully transparent devices would be enabled to achieve desirable gEL values (Figure 15b).[64]

    Figure 15

    Figure 15.  (a) The schematic diagram of CP-OLEDs with the architecture of full chiral layers (FCLs). (b) CP-OLEDs with a semi- or fully transparent cathode.[64] Copyright 2021, WILEY-VCH.

    Importantly, due to the complexity behind the CPEL phenomenon, a close collaboration between organic chemists and physicists appears essential to thoroughly understand and control the different aspects of molecular structure design and device engineering allowing the construction of applicable CP-OLEDs simultaneously displaying high EQE and gEL factors. Owing to the wide potential applications of CPEL in 3D displays, optical information storage, quantum communication, and biological sensors, we believe that with the rapid development of chiral emitting materials and device architectures, CPEL based on OLEDs will attract more interest and become a research hotspot of luminescent materials in the future.


    ACKNOWLEDGEMENTS: This work was supported by the National Natural Science Foundation of China (No. 22005158), the Program of High Level Talents (Nos. 03083064 and JSSCBS20211122), and Large Instruments Open Foundation of Nantong University. The authors declare no competing interests.
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    1. [1]

      Huck, N. P. M.; Jager, W. F.; Lange, B. D.; Feringa, B. L. Dynamic control and amplification of molecular chirality by circular polarized light. Science 1996, 273, 1686-1688. doi: 10.1126/science.273.5282.1686

    2. [2]

      Cao, Z.; Wang, B.; Zhu, F.; Hao, A.; Xing, P. Solvent-processed circularly polarized luminescence in light-harvesting coassemblies. ACS Appl. Mater. Interfaces 2020, 12, 34470-34478. doi: 10.1021/acsami.0c10559

    3. [3]

      Fan, H.; Li, K.; Tu, T.; Zhu, X.; Zhang, L.; Liu, M. ATP-induced emergent circularly polarized luminescence and encryption. Angew. Chem. Int. Ed. 2022, 61, e202200727.

    4. [4]

      MacKenzie, L. E.; Pal, R. Circularly polarized lanthanide luminescence for advanced security inks. Nat. Rev. Chem. 2021, 5, 109-124.

    5. [5]

      Zhang, D. W.; Li, M.; Chen, C. F. Recent advances in circularly polarized electroluminescence based on organic light-emitting diodes. Chem. Soc. Rev. 2020, 49, 1331-1343. doi: 10.1039/C9CS00680J

    6. [6]

      Li, X.; Xie, Y.; Li, Z. The progress of circularly polarized luminescence in chiral purely organic materials. Adv. Photonics Res. 2021, 2, 2000136. doi: 10.1002/adpr.202000136

    7. [7]

      Liu, L.; Yang, Y.; Wei, Z. Chiral organic optoelectronic materials and circularly polarized light luminescence and detection. Acta Chim. Sinica 2022, 80, 970-992. doi: 10.6023/A22030123

    8. [8]

      Ma, J. L.; Peng, Q.; Zhao, C. H. Circularly polarized luminescence switching in small organic molecules. Chem. Eur. J. 2019, 25, 15441-15454. doi: 10.1002/chem.201903252

    9. [9]

      Luo, X. Y.; Pan, M. Metal-organic materials with circularly polarized luminescence. Coordin. Chem. Rev. 2022, 468, 214640. doi: 10.1016/j.ccr.2022.214640

    10. [10]

      Zhang, Y.; Yu, S.; Han, B.; Zhou, Y.; Zhang, X.; Gao, X.; Tang, Z. Circularly polarized luminescence in chiral materials. Matter 2022, 5, 837-875. doi: 10.1016/j.matt.2022.01.001

    11. [11]

      Hasegawa, M.; Nojima, Y.; Mazaki, Y. Circularly polarized luminescence in chiral π-conjugated macrocycles. ChemPhotoChem 2021, 5, 1042-1058. doi: 10.1002/cptc.202100162

    12. [12]

      Gao, J. X.; Zhang, W. Y.; Wu, Z. G.; Zheng, Y, X.; Fu, D. W. Enantiomorphic perovskite ferroelectrics with circularly polarized luminescence. J. Am. Chem. Soc. 2020, 142, 4756-4761. doi: 10.1021/jacs.9b13291

    13. [13]

      Chen, Y. Circularly polarized luminescence based on small organic fluorophores. Mater. Today. Chem. 2022, 23, 100651. doi: 10.1016/j.mtchem.2021.100651

    14. [14]

      Ni, B.; Li, Y.; Liu, W.; Li, B.; Li, H.; Yang, Y. Circularly polarized luminescence from structurally coloured polymer films. Chem. Commun. 2021, 57, 2796-2799. doi: 10.1039/D1CC00201E

    15. [15]

      Liang, X.; Liu, T. T.; Yan, Z. P.; Zhou, Y.; Su, J.; Luo, X. F.; Wu, Z. G.; Wang, Y.; Zheng, Y. X.; Zuo, J. L. Organic room-temperature phosphorescence with strong circularly polarized luminescence based on paracyclophanes. Angew. Chem. Int. Ed. 2019, 58, 17220-17225. doi: 10.1002/anie.201909076

    16. [16]

      Roose, J.; Tang, B. Z.; Wong, K. S. Circularly-polarized luminescence (CPL) from chiral AIE molecules and macrostructures. Small 2016, 12, 6495-6512. doi: 10.1002/smll.201601455

    17. [17]

      Chen, N.; Yan, B. Recent theoretical and experimental progress in circularly polarized luminescence of small organic molecules. Molecules 2018, 23, 3376. doi: 10.3390/molecules23123376

    18. [18]

      Li, M.; Lin, W. B.; Fang, L.; Chen, C. F. Recent progress on circularly polarized luminescence of chiral organic small molecules. Acta Chim. Sinica 2017, 75, 1150-1163. doi: 10.6023/A17090440

    19. [19]

      Han, J.; Guo, S.; Lu, H.; Liu, S.; Zhao, Q.; Huang, W. Recent progress on circularly polarized luminescent materials for organic optoelectronic devices. Adv. Optical Mater. 2018, 6, 1800538. doi: 10.1002/adom.201800538

    20. [20]

      Zhou, L.; Xie, G.; Ni, F.; Yang, C. Emerging circularly polarized thermally activated delayed fluorescence materials and devices. Appl. Phys. Lett. 2020, 117, 130502. doi: 10.1063/5.0021127

    21. [21]

      Frédéric, L.; Desmarchelier, A.; Favereau, L.; Pieters, G. Designs and applications of circularly polarized thermally activated delayed fluorescence molecules. Adv. Funct. Mater. 2021, 31, 2010281. doi: 10.1002/adfm.202010281

    22. [22]

      Zhang, Y. P.; Zheng, Y. X. Frontiers in chiral phosphorescent complexes for circularly polarized electroluminescence. Dalton Trans. 2022, 51, 9966-9970. doi: 10.1039/D2DT01582J

    23. [23]

      Peeters, E.; Christiaans. M. P. T.; Janssen, R. A. J.; Schoo, H. F. M.; Dekkers, H. P. J. M.; Meijer, E. W. Circularly polarized electroluminescence from a polymer light-emitting diode. J. Am. Chem. Soc. 1997, 119, 9909-9910. doi: 10.1021/ja971912c

    24. [24]

      Liang, X.; Tu, Z. L.; Zheng, Y. X. Thermally activated delayed fluorescence materials: towards realization of high efficiency through strategic small molecular design. Chem. Eur. J. 2019, 25, 5623-5642. doi: 10.1002/chem.201805952

    25. [25]

      Wong, M. Y.; Zysman-Colman, E. Purely or ganic thermally activated delayed fluorescence materials for organic light-emitting diodes. Adv. Mater. 2017, 29, 1605444. doi: 10.1002/adma.201605444

    26. [26]

      Tao, Y.; Yuan, K.; Chen, T.; Xu, P.; Li, H.; Chen, R.; Zheng, C.; Zhang, L.; Huang, W. Thermally activated delayed fluorescence materials towards the breakthrough of organoelectronics. Adv. Mater. 2014, 26, 7931-7958. doi: 10.1002/adma.201402532

    27. [27]

      Yang, Z.; Mao, Z.; Xie, Z.; Zhang, Y.; Liu, S.; Zhao, J.; Xu, J.; Chi, Z.; Aldred, M. P. Recent advances in organic thermally activated delayed fluorescence materials. Chem. Soc. Rev. 2017, 46, 915-1016. doi: 10.1039/C6CS00368K

    28. [28]

      Im, Y.; Kim, M.; Cho, Y. J.; Seo, J. A.; Yook, K. S.; Lee, J. Y. Molecular design strategy of organic thermally activated delayed fluorescence emitters. Chem. Mater. 2017, 29, 1946-1963. doi: 10.1021/acs.chemmater.6b05324

    29. [29]

      Jeon, S. K.; Lee, H. L.; Yook, K. S.; Lee, J. Y. Recent progress of the lifetime of organic light-emitting diodes based on thermally activated delayed fluorescent material. Adv. Mater. 2019, 31, 1803524. doi: 10.1002/adma.201803524

    30. [30]

      Kim, K. H.; Kim, J. J. Origin and control of orientation of phosphorescent and TADF dyes for high-efficiency OLEDs. Adv. Mater. 2018, 30, 1705600. doi: 10.1002/adma.201705600

    31. [31]

      Zinna, F.; Giovanella, U.; Bari, L. D. Highly circularly polarized electroluminescence from a chiral europium complex. Adv. Mater. 2015, 27, 1791-1795. doi: 10.1002/adma.201404891

    32. [32]

      Zinna, F.; Pasini, M.; Galeotti, F.; Botta, C.; Bari, L. D.; Giovanella, U. Design of lanthanide-based OLEDs with remarkable circularly polarized electroluminescence. Adv. Funct. Mater. 2017, 27, 1603719. doi: 10.1002/adfm.201603719

    33. [33]

      Li, M.; Li, S. H.; Zhang, D.; Cai, M.; Duan, L.; Fung, M. K.; Chen, C. F. Stable enantiomers displaying thermally activated delayed fluorescence: efficient OLEDs with circularly polarized electroluminescence. Angew. Chem. Int. Ed. 2018, 57, 2889-2893. doi: 10.1002/anie.201800198

    34. [34]

      Li, T. Y.; Jing, Y. M.; Liu, X.; Zhao, Y.; Shi, L.; Tang, Z.; Zheng, Y. X.; Zuo, J. L. Circularly polarized phosphorescent photoluminescence and electroluminescence of iridium complexes. Sci. Rep. 2015, 5, 14912. doi: 10.1038/srep14912

    35. [35]

      Yang, S. Y.; Wang, Y. K.; Peng, C. C.; Wu, Z. G.; Yuan, S.; Yu, Y. J.; Li, H.; Wang, T. T.; Li, H. C.; Zheng, Y. X.; Jiang, Z. Q.; Liao, L. S. Circularly polarized thermally activated delayed fluorescence emitters in through-space charge transfer on asymmetric spiro skeletons. J. Am. Chem. Soc. 2020, 142, 17756-17765. doi: 10.1021/jacs.0c08980

    36. [36]

      Chen, Y.; Li, X.; Li, N.; Quan, Y.; Cheng, Y.; Tang, Y. Strong circularly polarized electroluminescence based on chiral salen-Zn(Ⅱ) complex monomer chromophores. Mater. Chem. Front. 2019, 3, 867-873. doi: 10.1039/C9QM00039A

    37. [37]

      Yang, Y.; Li, N.; Miao, J.; Cao, X.; Ying, A.; Pan, K.; Lv, X.; Ni, F.; Huang, Z.; Gong, S.; Yang, C. Chiral multi-resonance TADF emitters exhibiting narrowband circularly polarized electroluminescence with an EQE of 37.2%. Angew. Chem. Int. Ed. 2022, 61, e202202227.

    38. [38]

      Zhang, D. W.; Teng, J. M.; Wang, Y. F.; Han, X. N.; Li, M.; Chen, C. F. D-π*-A type planar chiral TADF materials for efficient circularly polarized electroluminescence. Mater. Horiz. 2021, 8, 3417-3423. doi: 10.1039/D1MH01404H

    39. [39]

      Wu, Z. G.; Han, H. B.; Yan, Z. P.; Luo, X. F.; Wang, Y.; Zheng, Y. X.; Zuo, J. L.; Pan, Y. Chiral octahydro-binaphthol compound-based thermally activated delayed fluorescence materials for circularly polarized electroluminescence with superior EQE of 32.6% and extremely low efficiency roll-off. Adv. Mater. 2019, 1900524.

    40. [40]

      Liang, Z. P.; Tang, R.; Qiu, Y. C.; Wang, Y.; Lu, H.; Wu, Z. G. Construction and properties of octahydrobinaphthol-based chiral luminescent materials with large steric hindrance. Acta Chim. Sinica 2021, 79, 1401-1408. doi: 10.6023/A21070355

    41. [41]

      Shen, Y.; Chen, C. F. Helicenes: synthesis and applications. Chem. Rev. 2012, 112, 1463-1535. doi: 10.1021/cr200087r

    42. [42]

      Zhao, W. L.; Li, M.; Lu, H. Y.; Chen, C. F. Advances in helicene derivatives with circularly polarized luminescence. Chem. Commun. 2019, 55, 13793-13803. doi: 10.1039/C9CC06861A

    43. [43]

      Shen, C.; Gan, F.; Zhang, G.; Ding, Y.; Wang, J.; Wang, R.; Crassous, J.; Qiu, H. Helicene-derived aggregation-induced emission conjugates with highly tunable circularly polarized luminescence. Mater. Chem. Front. 2020, 4, 837-844. doi: 10.1039/C9QM00652D

    44. [44]

      Zhao, Z. H.; Liang, X.; He, M. X.; Zhang, M. Y.; Zhao, C. H. Triarylborane-based [5]helicenes with full-color circularly polarized luminescence. Org. Lett. 2019, 21, 9569-9573. doi: 10.1021/acs.orglett.9b03734

    45. [45]

      Zhu, Y.; Xia, Z.; Cai, Z.; Yuan, Z.; Jiang, N.; Li, T.; Wang, Y.; Guo, X.; Li, Z.; Ma, S.; Zhong, D.; Li, Y.; Wang, J. Synthesis and characterization of hexapole[7]helicene, a circularly twisted chiral nanographene. J. Am. Chem. Soc. 2018, 140, 4222-4226. doi: 10.1021/jacs.8b01447

    46. [46]

      Zhang, S.; Liu, X.; Li, C.; Li, L.; Song, J.; Shi, J.; Morton, M.; Rajca, S.; Rajca, A.; Wang, H. Thiophene-Based Double Helices: Syntheses, X-ray Structures, and Chiroptical Properties. J. Am. Chem. Soc. 2016, 138, 10002-10010. doi: 10.1021/jacs.6b05709

    47. [47]

      Li, J. K.; Chen, X. Y.; Guo, Y. L.; Wang, X. C.; Sue, A. C. H.; Cao, X. Y.; Wang, X. Y. B, N-embedded double hetero[7]helicenes with strong chiroptical responses in the visible light region. J. Am. Chem. Soc. 2021, 143, 17958-17963. doi: 10.1021/jacs.1c09058

    48. [48]

      Yang, Y.; Correa da Costa, R.; Smilgies, D. M.; Campbell, A. J.; Fuchter, M. J. Induction of circularly polarized electroluminescence from an achiral light-emitting polymer via a chiral small molecule dopant. Adv. Mater. 2013, 25, 2624-2628. doi: 10.1002/adma.201204961

    49. [49]

      Wan, L.; Wade, J.; Salerno, F.; Arteaga, O.; Laidlaw, B.; Wang, X.; Penfold, T.; Fuchter, M. J.; Campbell, A. J. Inverting the handedness of circularly polarized luminescence from light-emitting polymers using film thickness. ACS Nano 2019, 13, 8099-8105. doi: 10.1021/acsnano.9b02940

    50. [50]

      Wan, L.; Wade, J.; Shi, X.; Xu, S.; Fuchter, M. J.; Campbell, A. J. Highly efficient inverted circularly polarized organic light-emitting diodes. ACS Appl. Mater. Interfaces 2020, 12, 39471-39478. doi: 10.1021/acsami.0c09139

    51. [51]

      Wan, L.; Wade, J.; Wang, X.; Campbell, A. J.; Fuchter, M. J. Engineering the sign of circularly polarized emission in achiral polymer-chiral small molecule blends as a function of blend ratio. J. Mater. Chem. C 2022, 10, 5168-5172. doi: 10.1039/D1TC05403A

    52. [52]

      Li, M.; Wang, Y. F.; Zhang, D. W.; Zhang, D.; Hu, Z. Q.; Duan, L.; Chen, C, F. Thermally activated delayed fluorescence material-sensitized helicene enantiomer-based OLEDs: a new strategy for improving the efficiency of circularly polarized electroluminescence. Sci China Mater. 2021, 64, 899-908. doi: 10.1007/s40843-020-1496-7

    53. [53]

      Dhbaibi, K.; Abella, L.; Meunier-Della-Gatta, S.; Roisnel, T.; Vanthuyne, N.; Jamoussi, B.; Pieters, G.; Racine, B.; Quesnel, E.; Autschbach, J.; Crassous, J.; Favereau, L. Achieving high circularly polarized luminescence with push-pull helicenic systems: from rationalized design to top-emission CP-OLED applications. Chem. Sci. 2021, 12, 5522-5533. doi: 10.1039/D0SC06895K

    54. [54]

      Hellou, N.; Srebro-Hooper, M.; Favereau, L.; Zinna, F.; Caytan, E.; Toupet, L.; Dorcet, V.; Jean, M.; Vanthuyne, N.; Williams, J. A. G.; Bari, L. D.; Autschbach, J.; Crassous, J. Enantiopure cycloiridiated complexes bearing a pentahelicenic N-heterocyclic carbene and displaying long-lived circularly polarized phosphorescence. Angew. Chem. Int. Ed. 2017, 56, 8236-8239. doi: 10.1002/anie.201704263

    55. [55]

      Brandt, J. R.; Wang, X.; Yang, Y.; Campbell, A. J.; Fuchter, M. J. Circularly polarized phosphorescent electroluminescence with a high dissymmetry factor from PHOLEDs based on a platinahelicene. J. Am. Chem. Soc. 2016, 138, 9743-9746. doi: 10.1021/jacs.6b02463

    56. [56]

      Yan, Z. P.; Luo, X. F.; Liu, W. Q.; Wu, Z. G.; Laing, X.; Liao, K.; Wang, Y.; Zheng, Y. X.; Zhou, L.; Zuo, J. L.; Pan, Y.; Zhang, H. Configurationally stable platinahelicene enantiomers for efficient circularly polarized phosphorescent organic light-emitting diodes. Chem. Eur. J. 2019, 25, 5672-5676. doi: 10.1002/chem.201900955

    57. [57]

      Yan, Z. P.; Luo, X. F.; Liao, K.; Zheng, Y. X.; Zuo, J. L. Rational design of the platinahelicene enantiomers for deep-red circularly polarized organic light-emitting diodes. Front. Chem. 2020, 8, 501. doi: 10.3389/fchem.2020.00501

    58. [58]

      Yuan, L.; Liu, T. T.; Mao, M. X.; Luo, X. F.; Zheng, Y. X. Configurationally stable helical tetradentate Pt(Ⅱ) complexes for organic light-emitting diodes with circularly polarized electroluminescence. J. Mater. Chem. C 2021, 9, 14669-14674. doi: 10.1039/D1TC03351D

    59. [59]

      Yuan, L.; Ding, Q. J.; Tu, Z. L.; Liao, X. J.; Luo, X. F.; Yan, Z. P.; Wu, Z. G.; Zheng, Y. X. Molecular self-induced configuration for improving dissymmetry factors in tetradentate platinum(Ⅱ) enantiomers cycloaddition. Chin. Chem. Lett. 2022, 33, 1459-1462. doi: 10.1016/j.cclet.2021.08.104

    60. [60]

      Wu, X.; Huang, J. W.; Su, B. K.; Wang, S.; Yuan, L.; Zheng, W. Q.; Zhang, H.; Zheng, Y. X.; Zhu, W.; Chou, P. T. Fabrication of circularly polarized MR-TADF emitters with asymmetrical peripheral-lock enhancing helical B/N-doped nanographenes. Adv. Mater. 2022, 34, 2105080. doi: 10.1002/adma.202105080

    61. [61]

      Yang, W.; Li, N.; Miao, J.; Zhan, L.; Gong, S.; Huang, Z.; Yang, C. Simple double hetero[5]helicenes realize highly efficient and narrowband circularly polarized organic light-emitting diodes. CCS Chem. 2022, 4, 3463-3471. doi: 10.31635/ccschem.022.202101661

    62. [62]

      Yang, S. Y.; Zou, S. N.; Kong, F. C.; Liao, X. J.; Qu, Y. K.; Feng, Z. Q.; Zheng, Y. X.; Jiang, Z. Q.; Liao, L. S. A narrowband blue circularly polarized thermally activated delayed fluorescence emitter with a heterohelicene structure. Chem. Commun. 2021, 57, 11041-11044. doi: 10.1039/D1CC04405B

    63. [63]

      Yang, S. Y.; Tian, Q. S.; Liao, X. J.; Wu, Z. G.; Shen, W. S.; Yu, Y. J.; Feng, Z. Q.; Zheng, Y. X.; Jiang, Z. Q.; Liao, L. S. Efficient circularly polarized thermally activated delayed fluorescence hetero-[4]helicene with carbonyl-/sulfone-bridged triarylamine structures. J. Mater. Chem. C 2022, 10, 4393-4401. doi: 10.1039/D1TC06125A

    64. [64]

      Lu, G.; Wu, Z. G.; Wu, R.; Cao, X.; Zhou, L.; Zheng, Y. X.; Yang, C. Semitransparent circularly polarized phosphorescent organic light-emitting diodes with external quantum efficiency over 30% and dissymmetry factor close to 10-2. Adv. Funct. Mater. 2021, 31, 2102898. doi: 10.1002/adfm.202102898

  • Figure 1  (a) The schematic diagram of the physical method versus (b) CP-OLEDs for obtaining CP light.

    Figure 2  Categories of chiral luminescent materials.

    Figure 3  Molecular structures of (M/P)-1-Aza[6] helicene and light-emitting polymer F8BT. (b) CPPL spectra of F8BT doped with (+)-1-Aza[6] helicene. (c) CPEL spectra.[48] Copyright 2013, WILEY-VCH.

    Figure 4  Molecular structures of the helicene enantiomers (P)-HAI and (M)-HAI. (b) CPEL spectra and gEL versus wavelength curves of the CP-OLEDs.[52] Copyright 2020, Science China Press.

    Figure 5  (a) Molecular structures and g values for each compound. (b) gPL and gEL based on (P) or (M)-H6(TMS)2.[53] Copyright 2021, Royal Society of Chemistry.

    Figure 6  Molecular structure of the helicene iridium complex A2.

    Figure 7  (a) Molecular structure of platinahelicene complex (+/-)-1. (b) gEL as a function of emission wavelength.[55] Copyright 2016, American Chemical Society.

    Figure 8  (a) Molecular structures of platinahelicene enantiomers (M)-Pt and (P)-Pt. (b) CPEL spectra and gEL versus wavelength curves. (c) CPEL spectra and gEL versus the wavelength curves of semitransparent electrode devices.[56] Copyright 2019, WILEY-VCH.

    Figure 9  (a) Molecular structures of (M/P)-Pt. (b) CPEL spectra and gEL versus wavelength curves.[57] Copyright 2020, Yan, Luo, Liao, Zheng and Zuo.

    Figure 10  (a) Molecular structures of the chiral Pt(Ⅱ) complexes. (b) CPEL spectra and gEL versus wavelength curves.[58] Copyright 2021, Royal Society of Chemistry.

    Figure 11  (a) Design strategy and molecular structures of chiral tetradentate Pt(Ⅱ) complexes. (b) CPPL spectra and gPL versus wavelength curves.[59] Copyright 2022, Elsevier.

    Figure 12  (a) Molecular structures of B/N nanographenes. (b) gEL versus wavelength curves.[60] Copyright 2021, WILEY-VCH.

    Figure 13  Molecular structure of (P/M)-helicene-BN and gEL values versus wavelength curves of (P/M)-helicene-BN based CP-OLEDs.[61] Copyright 2022, Chinese Chemical Society.

    Figure 14  (a) Molecular structures. (b) and (c) gEL versus wavelength curves.[62, 63] Copyright 2021, Royal Society of Chemistry.

    Figure 15  (a) The schematic diagram of CP-OLEDs with the architecture of full chiral layers (FCLs). (b) CP-OLEDs with a semi- or fully transparent cathode.[64] Copyright 2021, WILEY-VCH.

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  • 发布日期:  2022-12-02
  • 收稿日期:  2022-09-14
  • 接受日期:  2022-10-04
  • 网络出版日期:  2022-10-12
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