Pt(II) complexes featuring dicarbene pincer chelates have emerged as promising phosphors for the fabrication of blue organic light-emitting diodes (OLEDs); however, challenges persist in achieving both high-performance and concentration-independent color chromaticity. Herein, we present a series of Pt(II) complexes featuring a carbene pincer backbone and N-mesityl appendages, together with a complementary chloride and pyrazolate entity. These blue Pt(II) phosphors, Pt n , with n = 1-5, exhibit a high photoluminescence quantum yield (PLQY) and accelerated radiative transition rate constant (k r), while the corresponding chloride-to-pyrazolate substitution afforded the "AgCl"-coordinated products Pt3Ag and Pt4Ag in the presence of Ag2O. The representative phosphorescent OLED (PhOLED) based on Pt(II) phosphor Pt2 achieved a max. external quantum efficiency (EQE max) of 20.1% and a luminance exceeding 100,000 cd m-2, with no excimer emission even at high doping concentrations. Furthermore, upon the addition of the terminal emitter BCzBN, the resulting hyper-OLED device maintained high EQE values of 21.6% and 18.3% at 1000 and 10,000 cd m-2, respectively. These results validated the pivotal role of N-aryl substitution in carbene pincer chelates for developing Pt(II) emitters aimed at efficient blue PhOLED devices.

Near infrared (NIR) light-emitting devices hold significant promise for applications in night vision, telecommunications, and biomedical imaging. Hybrid tandem light-emitting diodes (LEDs) that combine quantum-dot (QD)-based and organic emissive subunits represent a compelling strategy to surpass an external quantum efficiency (EQE) of 30%. However, in series-connected architectures, the intrinsic mismatch in charge-transport properties and distinct efficiency roll-off characteristics between the two emissive units hinder ideal efficiency summation and limit overall device performance under identical current injection. Here, we report a high-performance hybrid NIR tandem LED in which this imbalance is mitigated by selectively enhancing carrier injection and transport in the performance-limiting QD-based emissive unit. Through molecular engineering of the electron-transporting layer and rational design of the charge-generation interface, the electrical characteristics of the QD unit is precisely tailored to match that of the high-efficiency organic NIR emitter. As a result, the hybrid tandem device achieves a near-ideal voltage addition and markedly improved electroluminescence, delivering a peak external quantum efficiency of 35% with stable emission at 780 nm. This work establishes a general design principle for overcoming current-driving imbalance in heterogeneous tandem architectures and paves the way toward high-performance NIR light sources.

We reported Ir(III) complexes featuring a dicarbene pincer chelate, a bidentate carbene cyclometalate (with either N-benzyl or N-mesityl appendage) and a halide (X− = Cl−, Br− and I−), for probing the structure-property relationship. They exhibit blue emission with the peakmax spanning 465–480 nm in toluene at RT. Particularly, [Ir(DP)(MC5H)Cl] and [Ir(DP)(MS1)Cl] showed the best performance among these Ir(III) emitters due to the high MLCT and LC components and relatively diminished XLCT contribution. This is evidenced by high photoluminescent quantum yield (PLQY) of 60

We synthesized four diiridium Janus carbene complexes, exhibiting emissions ranging from 422 nm to 451 nm with high photoluminescent quantum yields (PLQYs) of 44%–78%. These photophysical characteristics were verified using TD-DFT calculations.

Hair loss presents a widespread clinical and psychological challenge, yet conventional pharmacological treatments often incur systemic side effects such as hormonal imbalance and mood disturbances. To provide a non-pharmacological alternative, a wearable textile-integrated near-infrared (NIR) organic light-emitting diode (OLED) platform was developed with emission closely aligned with the action spectrum of human dermal papilla cells (hDPCs). By employing a top-emitting microcavity structure, we tuned the emission peak of the NIR OLEDs (around 730–740 nm) to align with the hDPC activation spectrum, thereby enhancing photon delivery to the follicle niche and enabling irradiation at wavelengths that promote hDPC photoactivation. This non‑invasive, skin‑conformable textile‑based device exhibits mechanical resilience to repeated bending at a radius of 2 mm, low heat generation to prevent skin burns, and waterproof performance under water immersion. In vitro, NIR irradiation from the customized microcavity‑tuned OLED device significantly reduced senescence-associated β-galactosidase activity by 91.6

Blue phosphors present a significant challenge in the development of organic light-emitting diodes (OLEDs). In this contribution, we designed a new class of bis-tridentate Ir(III) phosphors featuring two complementary carbene cyclometalates. They possessed efficient blue emission with short radiative lifetimes in both the solution and thin film states, which enhances the full utilization of electrically generated triplet excitons. Particularly, one PhOLED device had given an external quantum efficiency (EQE) of 16.2

Pt(II) complexes are known for their versatility in showing aggregation-induced emission. Herein, we report four Pt(II) complexes Pt-1, Pt-2, and Pt-3a/b featuring both the carbene cyclometalate (C^C) and chelating pyrazolate (N^N). We evaluated two synthetic methods: the first employed the carbene intermediate Pt-DMSO, followed by N^N coordination to give Pt-1-Cl and aryl cyclometalation, while the second involved sequential addition of C^C and N^N chelates to Pt(COD)Cl2. These Pt(II) complexes exhibited efficient sky-blue emission in a PMMA matrix at high dilution. Upon increasing the doping ratio, emission of Pt-1 and Pt-3a remained essentially unchanged, but Pt-2 and Pt-3b exhibited gradual emergence of a low-energy band at ∼575 nm, which was attributed to the metal-metal-to-ligand charge transfer emission band. These aggregation propensities aligned well with the time-dependent density functional theory calculations based on the dimers and trimers. For applications, the organic light-emitting diode devices based on Pt-1 exhibited blue emission with a max. external quantum efficiency (EQE) of 11.7% at 50 wt %, while Pt-2-based devices gave concentration-dependent emission with max. EQEs of 9.4, 11.3, and 7.1% and CIExy coordinates of (0.26, 0.45), (0.33, 0.47), and (0.45, 0.49) at 10, 50, and 100 wt %, respectively.

Ir(iii) carbene complexes are a class of promising phosphors used in constructing high-performance blue OLEDs. In this work, two series of efficient blue-emitting Ir(iii) carbene complexes, namely, f-ct3ax/bx and f-ct9ax/bx, were designed, synthesized and characterized. These Ir(iii) carbene complexes possessed bulky substituents (both 2-xylenyl and tert-butyl group) at both cyclometalating and non-coordinated aryl sites and a dislocated 6- or 5-cyano substituent on the imidazo[4,5-b]pyridin-2-ylidene fragment, achieving blue phosphorescence. These Ir(iii) emitters showed excellent photophysical properties in degassed toluene solution with high PLQYs (72-98%) and short radiative lifetimes (0.91-3.08 mu s), making them excellent candidates for the fabrication of blue PhOLEDs. As a result, the blue PhOLEDs based on f-ct9ax and f-ct9bx with a 5-cyano substituent exhibited maximum EQEs of 24.2% and 23.3%, respectively, which were higher than those of f-ct3ax and f-ct3bx with a 6-cyano substituent (EQEmax = 22.1% and 20.0%, respectively). Moreover, the hyper-OLEDs featuring the f-ct9ax sensitizer and v-DABNA terminal emitter delivered a narrowband blue emission with a peak maximum at 468 nm and CIEx,y coordinates of (0.123, 0.095). This champion device also achieved a highest maximum EQE of 31.9% and an EQE of 20.9% at a practical luminance of 1000 cd m-2. These results demonstrate the potential of these Ir(iii) carbene complexes in constructing blue OLEDs with high efficiency and color purity for future applications.

Near-infrared organic light-emitting diodes are attractive for a broad range of applications, including night-time surveillance and biomedical diagnostic and imaging systems. However, obtaining high device radiance, which is necessary for many applications, and maintaining high operational stability is challenging due to the rapid efficiency roll-off at a high current density. Here we develop near-infrared organic light-emitting diodes based on an acceptor-donor-acceptor organic semiconductor with greatly suppressed singlet-triplet annihilation rate and triplet lifetime, alleviating singlet quenching by long-lived triplets, thereby enabling an ultrahigh singlet density at high electrical excitation levels. Our devices exhibit J50 values of 59.2 A cm-2, that is, the current density at which the external quantum efficiency decreases to half its peak value of 1.34%. A high external quantum efficiency is also maintained over a six orders of magnitude range of current densities, at values above 5,000 A cm-2. The devices emit with the maximum radiance beyond 2,000 W sr-1 m-2 under a continuous electrical bias and 46,700 W sr-1 m-2 in the pulsed electrical operation. The half-lifetime is 35 h for an initial radiance of 100 W sr-1 m-2. We also achieve a high electrically injected singlet density of more than 1016 cm-3 at 1,000 A cm-2, which can sustain population inversion, indicating potential for organic lasers. These results pave the way for further developments of near-infrared organic light-emitting diodes as well as offer a potential route towards electrically driven organic laser diodes.

Despite the rapid advancements of organic light-emitting diode (OLED) technology, designing suitable blue emitters remains a great challenge in meeting future demands. In this study, two efficient blue-emitting Ir(iii) carbene complexes bearing 5-cyano-imidazo[4,5-b]pyridin-2-ylidene cyclometalates were designed, namely, f-ct3a and f-ct3b, instead of 6-cyano-imidazo[4,5-b]pyridin-2-ylidene cyclometalates as shown in f-ct9a-c. With the relocation of the cyano group, both complexes displayed blue emission peaking at similar to 468 nm in toluene. Moreover, they demonstrated high quantum yields (Phi PL >= 80%) and high radiative constant (kr >= 3.37 x 105 s-1) in both solution and co-doped thin films, indicating their great potential for the fabrication of OLED devices. Notably, the OLEDs employing f-ct3a or f-ct3b as dopants afforded electrophosphorescence at 476 nm with maximum external quantum efficiencies (max. EQE) of 25.5 and 26.8%, respectively. Furthermore, the hyper-OLED incorporating the sensitizer f-ct3b and terminal emitter nu-DABNA achieved a max. EQE of 29.0% with Commission Internationale de l'Eclairage (CIEx,y) coordinates of (0.124, 0.130). This narrowband blue emission (lambda max = 468 nm, FWHM = 22 nm) revealed efficient F & ouml;rster resonance energy transfer (FRET), boosting the max. luminance close to 10 000 cd m-2, which confirmed the excellent performance of Ir(iii) carbene complexes as both the phosphor dopants and FRET sensitizers.

Blue phosphorescent OLEDs (Ph-OLEDs) have long faced critical challenges in efficiency, stability and brightness, which are crucial for advanced display. Herein, we introduce two novel Ir(III) emitters featuring a 3,6-di( tert -butyl)-9H-carbazolyl (tBuCz) substituted tridentate carbene pincer ligand, significantly improving efficiency and stability. The tBuCz- m -CF3 and tBuCz- p -CF3 complexes are designed to enhance steric encumbrance and minimize exciton accumulation. These innovations lead to exceptional photoluminescence quantum yields (PLQY) of 98% and an impressive decay rate constant of 7.97 × 10 5 s −1 in doped thin films. The Ph-OLEDs emit blue light with a peak wavelength of 485 nm and CIE coordinates of (0.175, 0.446), exhibiting a peak external quantum efficiencies (EQE) of 31.62% and brightness up to 214,255 cd m −2 . Notably, they shown minimal efficiency roll-off, retaining an EQE of 27.76% at 10,000 cd m −2 , and 20.58% at 100,000 cd m −2 . These consistent performances across various brightness levels represent a significant milestone for blue Ph-OLED technology. The devices also exhibit impressive stability, with an operational lifetime (LT 50 , the time taken for luminance to decrease by 50%) reaching 1237 h at 1000 cd m −2 , setting new benchmarks for blue Ph-OLEDs. To enhance the color purity, hyper-OLEDs were developed with a full width at half maximum (FWHM) of 20 nm and the CIEy of 0.233, achieving an EQE m of 29.78% and LT 50 of 318 h at 1000 cd m −2 . We also fabricated the active-matrix (AM) blue Hyper-OLEDs with 400 pixels per inch to demonstrate their application in AM displays.

Through-space charge transfer (TSCT), rather than the commonly postulated metal-to-ligand charge transfer (MLCT) process, was proposed in getting the lowest lying excited state of newly designed Ir(III) blue phosphors. Accordingly, two benzo[ d ]imidazolylidene pro-chelates, L12H 2 + and L13H 2 + , one with two cyano groups at the peri -benzo and N -aryl pendent and the other with its peri -cyano group being replaced with methyl substituent, were employed in syntheses of Ir(III) complexes f -ct12b , c and f -ct13b , c . Notably, complexes f -ct12b , c exhibited the traditional MLCT process, while f -ct13b,c were dominated by the TSCT transition, resulting in a smaller S 1 –T 1 energy gap Δ E ST . Next, it prompted us to explore whether their long-lived emission originated from phosphorescence or thermally activated delayed fluorescence (TADF). Although temperature-dependent emission studies favor TADF, the unresolved concerns are still discussed in depth. For application, OLED with the TSCT-based dopant f -ct13b delivered a maximum external quantum efficiency (EQE) of 22.2% and a max. luminance of 10 000 cd m ‒2 , together with CIE xy of (0.155, 0.120). Moreover, the hyper-OLED with f -ct13c sensitizer and v -DABNA terminal emitter exhibited a max. EQE of 28.2% and CIE xy of (0.123, 0.129), demonstrating a new approach in developing efficient Ir(III) blue phosphors.

Ir(III) complexes are particularly noted for their excellent photophysical properties in giving blue OLED phosphors. In this study, two distinctive carbene pro‐chelates LAH2+ and LBH2+ (or LCH2+) were employed in preparation of heteroleptic Ir(III) complexes, to which LAH2+ bears a cyano substituted benzoimidazolium along with N‐mesityl appendage, while LBH2+ (or LCH2+) carries the symmetrical benzoimidazolium entity. Notably, the reversible equilibration at high temperature was observed for m, f‐ct14 and m, f‐ct15 with a single LA chelate. In contrast, only the mer‐substituted m‐ct16 was obtained upon employing two LA chelates. All Ir(III) complexes exhibited blue photoluminescence (ΦPL ≥ 78%) with short radiative lifetimes (τrad ≤ 1.05 µs) in solution. The Ph OLED device with m‐ct16 afforded an external quantum efficiency (EQE) of 22.8% at 5000 cd m‒2. Moreover, the hyper‐OLED based on m‐ct16 and v‐DABNA exhibited EQE1000 of 32.1% (EQE recorded at 1000 cd·m−2) and J90 of 15.0 mA cm‒2 (current density at 90% of max. EQE). Its suppressed efficiency roll‐off (EQE of 32.1% and 27.7% at 1000 cd·m‒2 and 10000 cd·m‒2) demonstrated a milestone in fabrication of blue OLED devices.

It is very challenging to achieve highly efficient and low roll‐off purple to deep‐blue organic light‐emitting diodes (OLEDs) due to the limited selection of suitable emitters. Herein, a series of Ir(III) phosphors‐bearing purinylidene‐based N‐heterocyclic carbene (NHC) chelates are reported, namely, f‐ct2a–d, which have successfully turned the emission peak maxima to the purple region (427–432 nm) in degassed toluene, together with high quantum yields of 77%–81%. Notably, f‐ct2b is further employed as the phosphorescent dopant in the fabrication of OLEDs to afford deep‐blue emission paking at 448 nm and an EQE of 6.7% at 100 cd m−2. Furthermore, a true‐blue hyperphosphorescent OLED with 21 wt% of f‐ct2a as sensitizer and 1 wt% of ν‐DABNA as terminal emitter is also fabricated, giving excellent performance with max. EQE up to 22.2% and an EQE of 19.2% at a brightness of 100 cd m−2.

Three novel asymmetric Ir(III) complexes have been rationally designed to optimize their emitting dipole orientations (EDO) and enhance light outcoupling in blue phosphorescent organic light-emitting diodes (OLEDs), thereby boosting their external quantum efficiency (EQE). Bulky electron-donating groups (EDGs), namely: carbazole (Cz), di-tert-butyl carbazole (tBuCz), and phenoxazine (Pxz) are incorporated into the tridentate dicarbene pincer chelate to induce high degree of packing anisotropy, simultaneously enhancing their photophysical properties. Angle-dependent photoluminescence (ADPL) measurements indicate increased horizontal transition dipole ratios of 0.89 and 0.90 for the Ir(III) complexes Cz-dfppy-CN and tBuCz-dfppy-CN, respectively. Analysis of the single crystal structure and density functional theory (DFT) calculation results revealed an inherent correlation between molecular aspect ratio and EDO. Utilizing the newly obtained emitters, the blue OLED devices demonstrated exceptional performance, achieving a maximum EQE of 30.7% at a Commission International de l'Eclairage (CIE) coordinate of (0.140, 0.148). Optical transfer matrix-based simulations confirmed a maximum outcoupling efficiency of 35% due to improved EDO. Finally, the tandem OLED and hyper-OLED devices exhibited a maximum EQE of 44.2% and 31.6%, respectively, together with good device stability. This rational molecular design provides straightforward guidelines to reach highly efficient and stable saturated blue emission.

Narrowband blue emitters are indispensable in achieving ultrahigh-definition OLED displays that satisfy the stringent BT 2020 standard. Hereby, a series of bis-tridentate Ir(III) complexes bearing electron-deficient imidazo[4,5-b]pyridin-2-ylidene carbene coordination fragments and 2,6-diaryloxy pyridine ancillary groups were designed and synthesized. They exhibited deep blue emission with quantum yields of up to 89% and a radiative lifetime of 0.71 μs in the DPEPO host matrix, indicating both the high efficiency and excellent energy transfer process from the host to dopant. The OLED based on Irtb1 showed an emission at 468 nm with a maximum external quantum efficiency (EQE) of 22.7%. Moreover, the hyper-OLED with Irtb1 as a sensitizer for transferring energy to terminal emitter v-DABNA exhibited a narrowband blue emission at 472 nm and full width at half-maximum (FWHM) of 24 nm, a maximum EQE of 23.5%, and EQEs of 19.7, 16.1, and 12.9% at a practical brightness of 100, 1000, and 5000 cd/m2, respectively.

Iridium(III) complexes are particularly noted for their excellent potentials in fabrication of blue organic light-emitting diodes (OLEDs), but the severe efficiency roll-off largely hampered their practical applications. To reveal the underlying characteristics, three Ir(III) complexes, namely f-ct5c, f-ct5d, and f-ct11, bearing imidazo[4,5-b]pyrazin-2-ylidene cyclometalates are prepared and characterized in detail. Both f-ct5c and f-ct5d (also their mixture f-ct5mix) gave intensive blue emissions peaking at approximate to 465 nm with short radiative lifetimes of 1.76 and 2.45 mu s respectively, in degassed toluene. Alternatively, f-ct11 with two 4-tert-butylphenyl substituents on each imidazo[4,5-b]pyrazin-2-ylidene entity, possessed a bluish-green emission (508 nm) together with an extended radiative lifetime of 34.3 mu s in the dispersed PMMA matrix. Consequently, the resulting solution-processed OLED with f-ct11 delivered a maximum external quantum efficiency (EQEmax) of 6.5% with serious efficiency roll-offs. In contrast, f-ct5mix based device achieved a high EQEmax of 27.2% and the EQE maintained at 23.0% of 1000 cd m-2. Furthermore, the hyper-OLEDs with f-ct5mix as the sensitizer and v-DABNA as the terminal emitter afford narrowed emission with a considerably high EQEmax exceeding 32%, affirming the potential of f-ct5mix to serve as both the emitter and sensitizer in OLEDs. A mixture of Ir(III) based blue emitters with cyclometalating imidazo[4,5-b]pyrazin-2-ylidene chelates, i.e., f-ct5mix, can be utilized as dopant sensitizer in generation of hyperphosphorescence from terminal emitter nu-DABNA, achieving a remarkable EQEmax approaching 32.0% and an EQE of 25.5% at practical brightness of 1000 cd m-2.image

Circularly polarized phosphorescent (CPP) materials, especially chiral platinum(II) complexes, which combine the advantages of both circularly polarized luminescence (CPL) and phosphorescence, show broad potential applications in chiral optoelectronic devices. Developing CPP emitters with both excellent chiroptical properties and high yield is urgently needed. Here, a chiral cation strategy is employed to construct the CPP Pt(II) complexes R/S-ABA[Pt(ppy)Cl-2] and R/S-MBA[Pt(ppy)Cl-2] through a simple one-step reaction with almost 100% yield. The circular dichroism and CPL spectra confirm that the chirality was successfully transferred to the [Pt(ppy)Cl-2](-) anion. The luminescence asymmetry factors (g(lum)) are +1.4/-1.8 x 10(-3) for R/S-ABA[Pt(ppy)Cl-2] and +4.4/-2.8 x 10(-3) for R/S-MBA[Pt(ppy)Cl-2]. The stronger chiroptical property of R/S-MBA[Pt(ppy)Cl-2] is attributed to the enhanced chiral structural deformation and better matched electric and magnetic transition dipole moments. This chiral cation strategy is confirmed to efficiently construct CPP Pt(II) complexes, which will accelerate the development of CPP emitters towards commercialization.

Improving light extraction efficiency is crucial for the practical use of organic light-emitting diodes (OLEDs). Despite numerous reported methods for light extraction, designing a wavelength-independent structure to effectively extract trapped photons from broadband emission OLEDs remains a challenge. In this study, we introduce a convex indium tin oxide (ITO) pattern as a straightforward and cost-efficient solution for light extraction in OLEDs. This technique involves micrometer-scale inclined planes along the ITO convex squares, disrupting the internal waveguiding of light through geometrical optics and enabling wavelength-independent light extraction. Consequently, we observe substantial enhancements in the external quantum efficiency of blue, green, red, and near-infrared OLEDs by 34.5%, 22.4%, 28.6%, and 31.3%, respectively. Moreover, the patterning method for the ITO is fully compatible with existing lithographic production lines, offering a scalable and promising approach for mass production. Micrometer-scale ITO convex matrixes are used to improve the light extraction efficiency of OLEDs. Through optical manipulation, this scheme enhances the EQEs by up to 34.5% for blue, 22.4% for green, 28.6% for red, and 31.3% for NIR OLEDs.