Blue Light-emitting Materials Research Articles

Ultrafast dynamics and electroluminescence performance of a novel tetraphenylethylene-based aggregation induced emission luminogen

Efficient emission and confined molecular conjugation in aggregated/solid form, are two beneficial characteristics of blue organic light-emitting materials (OLEMs). Aggregation-induced emission molecules (AIEgens) have evolved as auspicious OLEMs that possess these properties. Herein, we discover an innovative sky-blue tetraphenylethene-based AIEgen, 4′,4‴-(1-phenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole-4,5-diyl)bis(N,N-diphenyl-[1,1′-biphenyl]-4-amine) (2TPA-ITPE), with high thermal stability. By employing this AIEgen as a non-doped emitter, the constructed organic light-emitting diode demonstrates a maximum external quantum efficiency of 3.35 % with a power efficiency of 4.1 lm/W and high luminescence of 15896.92 cd/m2 2TPA-ITPE exhibits a weak donor-acceptor character. Moreover, to probe the photo-physical nature of this AIEgen, its excited-state dynamics are examined through ultrafast transient absorption spectroscopy (TAS). The TAS results of this OLEM unveil the generation of a resonant structure species owing to the elongation of C=C double bond. The excited state dynamics reveal that 2TPA-ITPE undergoes three processes after excitation (internal conversion, C=C elongation and vibrational cooling). These findings offer innovative insights into the ultrafast mechanisms underlying excited TPE-based OLEMs.

Blue polyimides for high-performance solution-processable organic light-emitting diodes

Blue light-emitting materials with excellent film-forming ability, superior morphological stability, outstanding color purity, and high device efficiency are in urgent demand for new-generation display and solid-state lighting devices fabricated by low-cost wet processing. However, their current performances are far from satisfactory. Herein, two polyimide (PI)-based blue polymers are first precisely constructed and synthesized through a “Hinge-type Linking” strategy. A small molecular is introduced into the PI backbone via non-conjugated aliphatic imide ring linker. These polymers not only show superb thermal stability and morphological stability, but also maintain narrowband blue emission. Furthermore, PIs are prepared by polycondensation method, precipitated and purified in ethanol solvent, which avoids the use of metal catalysts. The resulting solution-processable devices achieve high performance with a maximum external quantum efficiency (EQE) of 9.94 % and maximum emission peak at 460 nm. To the best of our knowledge, this is the first time that solution-processable polymer light-emitting diodes (PLEDs) based on the “hot exciton” mechanism achieving splendid performance with maximum EQE close to 10 %. The superior performance is attributed to the validity of the “Hinge-type Linking” strategy in PLEDs, opening up a new avenue for PLED development and application.

Metal Halide Single Crystals RbCdCl3:Sn2+ and Rb3SnCl7 with Blue and White Emission Obtained via a Hydrothermal Process.

Until now, effective blue light-emitting materials are essentially needed for the creation of white light and precise color renderings in real-world applications, but the efficiency of blue light-emitting materials has lagged far behind. Here, we present a hydrothermal method to synthesize tin-based metal halide single crystals (RbCdCl3:Sn2+ and Rb3SnCl7). Two single crystal materials with different shapes and phases can simultaneously be synthesized in the same stoichiometric ratio. Rb3SnCl7 has a bulk shape, while RbCdCl3:Sn2+ has a needle shape. The deep blue emission (436 nm) of RbCdCl3:Sn2+ can be obtained under the optimal excitation wavelength irradiation. However, pure blue emission (460 nm) to white light can be obtained by changing the excitation wavelength in Rb3SnCl7. The refinement spectra of the electronic structures of RbCdCl3:Sn2+ and Rb3SnCl7 are investigated by density functional theory. It is concluded that the difference in the distribution of Cl energy states leads to the existence of Cl local defect states, which is the reason for the rich luminescence of the two single crystals. These findings provide a path for realizing single-phase broadband white-emitting materials.

Highly emissive tridentate fluorophores based on bis-imidazo[1,2-α]pyridine for deep-blue photoluminescence with CIE y ≤ 0.08

Imidazo[1,2-α]pyridine-based multifunctional derivatives have been widely utilized in pharmaceuticals, chemical sensing, bioimaging, optoelectronics, and other fields. Through incorporation of different substituents at the C4 position of central pyridine ring, nine tridentate imidazo[1,2-α]pyridine derivatives 4a-i have been synthesized and fully characterized. The influence of substituents on the luminescence of 4a-i was systematically investigated by spectroscopic methods, which was in accordance with density functional theory calculations and electrochemical measurement. In CH2Cl2, all compounds exhibited strong near-UV to deep-blue emission and retained CIE y coordinates ≤0.08, with maximum emission band located at 378–450 nm and photoluminescence quantum yields in the range of 15%–94%. Meanwhile, compound 4f exhibited a positive acidochromism in CH2Cl2 upon addition of TFA, accompanied with the dual change of colorimetric and fluorometric determination, indicating its potential application for the development of pH sensor. Moreover, the high decomposition temperatures of 4a-i ranging from 289 °C to 450 °C indicated that these compounds showed good thermal stability. On the basis of their excellent photophysical and thermal properties, the electroluminescence performance of 4f were further evaluated with a maximum EQE of 3.14% and CIE coordinate (0.16, 0.08), which could be utilized as promising novel blue organic light-emitting material.

Tuning photophysical properties of bicarbazole-based blue TADF emitters with AIE feature: Trade-off between small singlet-triplet energy splitting and high photoluminescence quantum yield

Three aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) blue light-emitting materials were successfully synthesized using bicarbazole and phenylsulfonyl/benzophenone moieties as electron donors and acceptors, respectively, via Buchwald-Hartwig reaction. Density functional theory calculations showed that the three emitters have a moderate dihedral angle between the two carbazole planes and between the donor and acceptor, resulting in a good conjugated structure and a trade-off between the small ΔEST and high photoluminescence quantum yield of the BCzDPM molecule. The cyclic voltammetry, thermogravimetric analysis and differential scanning calorimetry tests demonstrated that the three materials had high electrochemical and thermal stability. The three emitters exhibited obvious intramolecular charge transfer characteristics in solution and film. According to the fluorescence and low-temperature phosphorescence spectra, the lowest singlet and triplet excited state energy levels of BCzDPM were 2.96 eV and 2.78 eV, respectively, with a ΔEST of 0.18 eV. Using these emitters as non-doped emissive layers, efficient blue electroluminescent devices were fabricated. The maximum current efficiency and external quantum efficiency reached 15.4 cd/A and 7.05% for the BCzDPM device, respectively, and the efficiency roll-off of BCzDPM was smaller than that of PSOBCz and PBCzPM, under high current density.

One-Pot Synthesis of All-Inorganic CsPbClBr2 Blue Perovskite Quantum Dots via Stoichiometric Precursor.

The synthesis of perovskite-based blue light-emitting particles is valuable for several applications as the excellent optical properties and performances of the constituting materials associated with multi-exciton generation can be exploited. However, the preparation of perovskite precursors requires high temperatures, resulting in a complex manufacturing process. This paper proposes a one-pot method to synthesize CsPbClBr2 blue light-emitting quantum dots (QDs). In the case of nonstoichiometric precursor synthesis, the CsPbClBr2 QDs coexisted with additional products. The solvent for synthesizing mixed perovskite nanoparticles (containing chloride) was selected by mixing dimethylformamide (DMF) and/or dimethyl sulfoxide (DMSO) in different ratios. When only DMF was used with the stoichiometric CsBr and PbX2 (X = Cl, Br) ratio, the quantum yield was 70.55%, and superior optical properties were achieved. Moreover, no discoloration was observed for 400 h, and a high photoluminescence intensity was maintained. When deionized water was added to form a double layer with hexane, the luminescence was maintained for 15 days. In other words, the perovskite did not easily decompose even when in contact with water, which suppressed the release of Pb2+, which are heavy metal atoms in the structure. Overall, the proposed one-pot method for all-inorganic-based perovskite QDs provides a platform for synthesizing superior blue light-emitting materials.

Blue Organic Light Emitting Diode Materials based on Different Light-emitting Groups

Abstract: Organic light emitting diode (OLED) is a device that uses organic semiconductor materials to emit light under the action of an electric field. Compared with traditional luminescent materials, they have the advantages of good softness, low-temperature resistance, wider field of vision and low energy consumption, and have been widely used in the field of display and lighting in recent years. In addition, compared with red and green light-emitting materials, the maximum external quantum efficiency of blue-light materials-based devices is high, but the CIE coordinate performance is poor and the blue emission is difficult to achieve high efficiency and high color purity at the same time. Researchers continue to design new molecular structures in order to synthesize new high-efficiency blue light materials. It is found that different molecular structures have different effects on the performance of OLED devices. In the design and synthesis of blue-light materials, various light-emitting groups are often used to regulate the stability, singlet-third-line state of the target molecule energy level difference, excited state lifetime, aggregation state structure, electricity luminescent color and its OLED performance, etc. The introduction of different lightemitting groups into the blue light material greatly improves the performance of the material. This paper mainly reviews the research status of blue organic electroluminescent materials in the past five years from different molecular structures, further discusses the photoelectric properties of each compound and the properties of devices based on this material, and briefly analyzes the advantages of molecular design and device production. And finally discusses the improvement methods of blue OLED light-emitting materials in order to provide a reference for future research.

A Review on the Milestones of Blue Light-Emitting Materials in India

Since 1987 in the field of optoelectronics, organic light-emitting diodes (OLEDs) have secured their position because of their extreme use in panels of lighting applications such as TV and smartphone displays. At present, OLEDs are at top-notch position in the lighting market for their promising features. The field of OLEDs is rapidly growing day by day in academia and industry due to the success of OLEDs in the form of excellent efficiency, feasible methods, excellent lifetime, color purity, and superb device architecture. As a result, OLEDs are new profitable leading devices of the 21st century. However, the OLED industry has evolved in optoelectronics in the last 30 years and is advancing rapidly just because of the development in OLED materials (fluorescent, phosphorescent, thermally activated delayed fluorescent, and blue light-emitting materials). Blue light-emitting materials have achieved incredible popularity nationally and internationally. At the international level, USA, Japan, Korea, and Germany are at the top of the list in the production of OLEDs. India has also seen rapid progress in OLED development in the last 12 years and details of research in blue OLEDs by key players of India are involved in this report.1 Introduction1.1 OLED Construction1.2 Working of OLED2 OLED Development2.1 Historical Background of OLED2.1.1 International Status2.1.2 National Status3 Progress of Blue Emitters in India4 Present Scenario of Blue OLEDs5 Conclusions and Outlook

Recent Progress of Blue-light Emitting Materials for Organic Light-emitting Diodes

æœ‰æœºå‘å ‰äºŒæžç®¡ï¼ˆOrganic light‑emitting diodes，OLEDs）经过30ä½™å¹´çš„å‘å±•ï¼Œåœ¨æ˜¾ç¤ºå’Œç §æ˜Žé¢†åŸŸå·²ç»è¿›å ¥äº†å¤§è§„æ¨¡åº”ç”¨çš„é˜¶æ®µã€‚æœ‰æœºçº¢å ‰åŠç»¿å ‰OLEDsåŸºæœ¬ä¸Šå·²èƒ½å¤Ÿè¾¾åˆ°å•†ä¸šåº”ç”¨çš„æ ‡å‡†ï¼Œä½†æ˜¯è“å ‰OLEDsä»ç„¶å­˜åœ¨äº®åº¦ä½Žã€é«˜äº®åº¦ä¸‹å¯¿å‘½çŸ­çš„é—®é¢˜ï¼Œå› è€Œå•†ä¸šä¸Šå¯¹å ¼å ·é«˜æ¿€å­åˆ©ç”¨çŽ‡åŠé«˜ç¨³å®šæ€§çš„è“å ‰ææ–™å’Œå™¨ä»¶çš„éœ€æ±‚æ˜¾å¾—å°¤ä¸ºè¿«åˆ‡ã€‚ä¸ºäº†è§£å†³è¿™ä¸€é—®é¢˜ï¼Œå›½å† å’Œå›½é™ ä¸Šç›¸ç»§æå‡ºäº†åŸºäºŽé‡é‡‘å±žé ä½çš„ç£·å ‰é åˆç‰©ã€ä¸‰çº¿æ€â€ä¸‰çº¿æ€æ¹®ç­ã€çƒ­æ´»åŒ–å»¶è¿Ÿè§å ‰ã€â€œçƒ­æ¿€å­â€ç­‰ææ–™ç»“æž„çš„è®¾è®¡ç­–ç•¥ï¼ŒæœŸæœ›åœ¨èŽ·å¾—é«˜å‘å ‰é‡å­æ•ˆçŽ‡å’Œæ¿€å­åˆ©ç”¨çŽ‡çš„åŒæ—¶ï¼Œå°½é‡å‡å°å™¨ä»¶çš„æ•ˆçŽ‡æ»šé™ï¼ŒèŽ·å¾—å ·æœ‰é«˜ç¨³å®šæ€§ã€é•¿å¯¿å‘½çš„è“å ‰OLEDså™¨ä»¶ã€‚æœ¬æ–‡æ€»ç»“äº†ä¸åŒç±»åž‹è“å ‰OLEDsææ–™çš„ç ”ç©¶è¿›å±•ï¼Œå¹¶å¯¹æœªæ¥è“å ‰ææ–™çš„å‘å±•è¶‹åŠ¿è¿›è¡Œäº†å±•æœ›ã€‚

Cage Bismuth Metal–Organic Framework Materials Based on a Flexible Triazine–Polycarboxylic Acid: Subgram Synthesis, Application for Sensing, and White Light Tuning

Bismuth-based metal-organic frameworks (MOFs) have always attracted the attention of many researchers. Here, we first report a crystalline Bi-MOF (Bi-TDPAT) based on a flexible triazine-polycarboxylic linker 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine (H6TDPAT) and bismuth nitrate; its crystallite quality is adequately good and the diffraction data can be collected directly by single crystal X-ray diffraction rather than 3D electron diffraction. The structure of Bi-TDPAT belongs to a novel topology type btt. Notably, the synthesis scale of Bi-TDPAT can be expanded, and sub-gram synthesis can be realized. At the same time, we synthesized a microcrystalline material Bi-TATAB utilizing 2,4,6-tris(4-carboxylphenylamino)-1,3,5-triazine (H3TATAB). The structures of the two materials were characterized by several microanalysis tools. Considering that Bi-TDPAT is a blue light-emitting material with a broad emission peak, we prepared a white light emitting composite material Eu/Tb@Bi-TDPAT by encapsulating Eu(III)/Tb(III) in Bi-TDPAT. In addition, the fluorescence sensing functions of Bi-TDPAT and Bi-TATAB were explored. The results showed that they could detect and recognize various nitrophenols, and the optimal limit of detection is as low as 0.21 μM, which can be reused even after five cycles. Energy competitive absorption (CA) and photo-induced electron transfer are the main sensing mechanisms. By comparing and analyzing the properties of these two bismuth-based crystalline materials, we believe that this work also provides inspiration for the synthesis and development of bismuth-based MOF in the future.

Mild donor-π-mild acceptor (mD-π-mA) benzimidazole-based deep blue fluorophores with hybridized local and charge transfer (HLCT) excited states for OLEDs

The design of an efficient pure blue emitter to achieve stable, long operating organic light-emitting diode (OLED) devices still poses a significant challenge. Although through phosphorescence and thermally activated delayed fluorescence concepts, efficient and stable monochrome green and red OLEDs can be realized, the design of stable and efficient blue emitter has been a significant challenge. All efforts so far have resulted in severe efficiency roll-off and limited device lifetime. Therefore, developing efficient blue-emitting fluorescence materials with little or no efficiency roll-off is of great importance for commercial display OLEDs. In this context, we have designed and synthesized two pure blue fluorescence light-emitting materials that are thermally stable and have improved photophysical properties: 2-(4″-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-yl)-1-phenyl-1H-benzo[d]imidazole (PTBIBI) and 2-(4′′-(4,5-diphenyl-1-(3-(trifluoromethyl)phenyl)-1H-imidazol-2-yl)-[1,1′:4′,1′′-terphenyl]-4-yl)-1-phenyl-1H-benzo[d]imidazole (MCFBIBI). These emitters possess a hybrid local and charge-transfer (HLCT) state and have high photoluminescence quantum yields (>90%). The doped devices based on PTBIBI display a reasonably good device performance with the Commission International de l’Eclairage (CIE) coordinates of (0.15, 0.06) in the deep blue region and g maximum luminance of 6559 cd m−2 at a very low turn-on voltage (3.2 V) corresponding to the bandgap value of the blue emitter.

Synthesis and electrical properties of new blue emitter having boron atom and anthracene moiety

Boron-based blue light-emitting materials, 3,11-bis(10-phenylanthracen-9-yl)-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene [PA-DOBNA] was prepared with the composition of DOBNA core moiety and 9-phenylanthracene (PA) moiety as side group. The synthesized material showed excellent thermal stability with a high Td of > 400 °C. The doped device using dopant exhibited current efficiency (CE) of 2.90 cd/A and EQE of 4.40% at a current density of 10 mA/cm2. Commission Internationale de L’Eclairage (CIE) coordinates for non-doped and doped devices are (0.16, 0.18) and (0.15, 0.06) corresponding to the EL peaks at 457 and 446 nm, respectively. In addition, the doped device data showed a deep-blue emission of CIE (x = 1.15, y = 0.06) suitable for UHD-TV.

Synthesis and photophysical properties of quinoxaline-based blue aggregation-induced emission molecules

A series of quinoxaline-based compounds 1–4 have been synthesized by a palladium-catalyzed cross-coupling reaction and their photophysical properties have been extensively studied. Compounds 1–4 show deep blue light emission both in solution (λem ≤ 425 nm, Commission Internationale de L’Eclairage y (CIEy) ≤ 0.03) and in the solid state. Moreover, compounds 1–3 show a non-typical aggregation-induced enhanced emission (AIEE), which would be effective deep blue light-emitting materials. The DFT calculation indicated that the HOMO energy levels of compounds 1–3 are distributed throughout the molecule, and the LUMO energy levels are mainly concentrated on the quinoxaline group. However, the HOMO of compound 4 is mainly on the benzene ring at 2,3 position, and the LUMO is distributed both of the quinoxaline and the benzaldehyde group at the 6,7 position.

Thermally Activated Delayed Fluorescence Enabled by Reversed Conformational Distortion for Blue Emitters.

In this work, we present for the first time a general strategy via molecular reversed conformational distortion for thermally activated delayed fluorescence (TADF). A model purely organic compound named BNNIO with a common fluorophore flexibly linked to benzene by an oxygen atom is rationally designed and successfully synthesized. Moreover, the rate constant of reverse intersystem crossing reaches 2.34 × 104 s-1 as determined by transient spectroscopy. As a result, TADF emission of BNNIO is observed with a photoluminescence quantum yield of 90.72% and a lifetime of 84.76 μs at 415 nm. This universal regulation strategy undoubtedly opens a new avenue for the development of novel purely organic blue light-emitting materials.

Highly efficient nondoped blue electroluminescence based on hybridized local and charge-transfer emitter bearing pyrene-imidazole and pyrene

• A high-efficiency blue emitter is obtained based on pyrene[4,5- d ]imidazole and pyrene. • The nondoped blue OLED shows the maximum EQE of 9.13% with maximum exciton utilization efficiency of 65%. • Extremely small efficiency roll-offs of 0.9% and 6.9% are realized at high brightness of 10,000 and 50000 cd m −2 . Organic light-emitting diodes (OLEDs) have been explored and utilized in many fields of flat-panel displays nowadays because of their plentiful advantages such as lightweight, high flexibility, high picture quality, etc., and are hopeful to be the next-generation displays. However, improvements to the efficiency of blue OLEDs are still vital to OLEDs as replacements for liquid crystal display technology. A blue light-emitting material is one of the key components in the preparation of OLED displays. Designing molecule based on donor–acceptor (D-A) structure with a hybridized local and charge transfer (HLCT) excited state is a appealing strategy for providing an efficient OLED with high external quantum efficiency through efficacious exciton utilization. Herein, a highly efficient blue emitter, PyI-Py, is constructed combining pyrene[4,5- d ]imidazole (weak donor) and pyrene (weak acceptor). The non-doped blue OLED exhibits excellent performance with a maximum current efficiency of 15.74 cd A −1 , a maximum external quantum efficiency (η ext ) of 9.13% and a maximum brightness of as high as 91097 cd m −2 which is rarely obtained for a non-doped blue OLED. Moreover, the η ext can reach 9.05% at very high brightness of 10000 cd m −2 , displaying extremely low efficiency roll-off of 0.9% which displays great superiorities in contrast with most thermally activated delayed fluorescent materials. The device characteristics lie among the highest values in non-doped blue OLEDs based on HLCT emitter and correspond to the best performance achieved for non-doped pyrene-based blue OLEDs to date. A maximum exciton utilization efficiency of 65% is harvested. The superior performance is attributed to the proper donor–acceptor design strategy which results in a HLCT excited state with the generation of a high proportion of singlet excitons.

Efficient blue fluorescent electroluminescence based on a simple multifunctional tetraphenylethylene–triazole hybrid material with aggregation-induced emission characteristics

Although considerable progress has been achieved in organic electroluminescence (EL) fields based on aggregation-induced emission (AIE) effect emitters, highly efficient and multifunctional blue fluorophores with the AIE effect are still limited. In this work, a simple blue fluorescent molecule 3,4-diphenyl-5-(4ʹ-(1,2,2-triphenylvinyl)-[1,1ʹ-biphenyl]-4-yl)-4 H -1,2,4-triazole (TPETAZ) with the evident properties of AIE has been designed and synthesized based on tetraphenylethylene–triazole hybrid. The AIE-active molecule TPETAZ can act as both intrinsic blue light-emitting and electron-transporting layer in organic light-emitting diodes (OLEDs). Nondoped Device I with TmPyPB layer exhibits a maximal external quantum efficiency (EQE) of 2.4%, a maximum luminance (L) of 1020 cd m −2 , and maximal EL emission peak of 468 nm. Even though Device II without a TmPyPB layer exhibited excellent performance, the maximal EQE was observed to be 2.0%, indicating a decrease of only 18% when compared with that of Device I. However, the maximal EL emission peak remains almost unchanged (~470 nm). Furthermore, efficient doped Device III can be obtained by doping the host with TPETAZ as the blue light-emitting material. A maximal EQE of 4.1% was obtained, which was greater than those of Devices I and II by 42% and 52%, respectively; this can be attributed to the effective recombination of electron and hole carriers. This work provides a valuable strategy for designing highly efficient multifunctional blue EL AIE-active fluorophores, which have significant potential for practical applications. • An AIE-active blue-light emitter (TPETAZ) is designed and synthesized. • TPETAZ shows obvious aggregation-induced emission properties. • TPETAZ exhibits a photoluminescence quantum yield of 75.7% in film. • Non-doped OLED without electron-transporting material exhibits an EQE max of 2.0%.

Rare-Earth-Free Barium Borostannate with Deep-Blue Light Emission

Playing a crucial role in light-emitting diode (LED) illumination sources, the blue light-emitting materials are commonly obtained by doping rare-earth metal ions. Considering the high price, non-r...

Substituent-Mediated Transformation of Polynuclear Gold(I)-Sulfido Complexes—From Pentanuclear to Octadecanuclear Cluster-to-Cluster Transformation

Substituent-Mediated Transformation of Polynuclear Gold(I)-Sulfido Complexes—From Pentanuclear to Octadecanuclear Cluster-to-Cluster Transformation

Operando direct observation of spin-states and charge-trappings of blue light-emitting-diode materials in thin-film devices

Spin-states and charge-trappings in blue organic light-emitting diodes (OLEDs) are important issues for developing high-device-performance application such as full-color displays and white illumination. However, they have not yet been completely clarified because of the lack of a study from a microscopic viewpoint. Here, we report operando electron spin resonance (ESR) spectroscopy to investigate the spin-states and charge-trappings in organic semiconductor materials used for blue OLEDs such as a blue light-emitting material 1-bis(2-naphthyl)anthracene (ADN) using metal–insulator–semiconductor (MIS) diodes, hole or electron only devices, and blue OLEDs from the microscopic viewpoint. We have clarified spin-states of electrically accumulated holes and electrons and their charge-trappings in the MIS diodes at the molecular level by directly observing their electrically-induced ESR signals; the spin-states are well reproduced by density functional theory. In contrast to a green light-emitting material, the ADN radical anions largely accumulate in the film, which will cause the large degradation of the molecule and devices. The result will give deeper understanding of blue OLEDs and be useful for developing high-performance and durable devices.

Immobilization of dipyrenylphosphinic acid to boehmite: Fluorescent hybrid with weakened pyrene-aggregation

Ethyldipyrenylphosphate (DPyPOOEt) was designed and synthesized by utilizing ethyldichlorophosphate as the core and 1-bromopyrene as substituting groups, and afterwards dipyrenylphosphinic acid (DPyPOOH) was synthesized by the hydrolysis reaction of DPyPOOEt by using bromotrimethylsilane (TMSBr). Fluorescent hybrid was finally prepared by the dehydration condensation between DPyPOOH and hydroxyl groups on the surface of boehmite. The chemical structure of DPyPOOEt and DPyPOOH were characterized by 1H NMR and 13C NMR. Crystal structure, chemical structure and microtopography of hybrid were characterized by X-ray diffraction spectra (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), respectively. The results demonstrate that the incorporation of two pyrene substituent groups into phosphine oxide can be successfully immobilized on the surface without any change of crystal structure of boehmite. Fluorescence spectra in solution and powder further demonstrated the occurrence of shape-changed and red-shifted emission peaks of DPyPOOEt and DPyPOOH than that of pyrene. In particular, compared to DPyPOOEt and DPyPOOH in solid, the hybrid shows blue-shifted fluorescence. Optimized molecular conformation, ground electronic structure of DPyPOOEt has been investigated in detail by quantum chemistry method. The introduction of phosphine oxide tunes the conjugated structure of pyrene-ring and spatial conformation between the pyrene-ring. In addition, intramolecular V-shanped conformation when DPyPOOH confined to boehmite surface reduce π-π aggregation between pyrene rings. Therefore, these results indicate that the hybrid is expected to highly efficient blue light-emitting material.