Organic Light-emitting Diodes Research Articles

Chiral Organometallic Complexes Derived from Helicenic N-Heterocyclic Carbenes (NHCs): Design, Structural Diversity, and Chiroptical and Photophysical Properties.

ConspectusRecently, helicene derivatives have emerged as an important class of molecules with potential applications spanning over asymmetric catalysis, biological activity, magnetism, spin filtering, solar cells, and polymer science. To harness their full potential, especially as emissive components in circularly polarized organic light-emitting diodes (CP-OLEDs), generating structural chemical diversity and understanding the resulting photophysical and chiroptical properties are crucial. In this Account, we shed light on chemical engineering combining helicene and N-heterocyclic carbene (NHC) chemistries to create transition-metal complexes with unique architectures and describe their photophysical and chiroptical attributes. The σ-donating and π-accepting capabilities of the helically chiral π-conjugated NHCs endow the complexes with remarkable structural and electronic features. These characteristics manifest in phenomena such as chirality induction, very long-lived phosphorescence, and strong chiroptical signatures (electronic circular dichroism and circularly polarized luminescence).We describe the different classes of ligands primarily developed in our group by classifying them according to their connection between the helicenic moiety and the imidazole precursor. This connection is essential in determining the degree of π-conjugation and characterizing the emissive state. We comprehensively discuss 6-coordinate, 4-coordinate, and 2-coordinate complexes, delving into their structural nuances and examining how the interplay between metals and auxiliary ligands shapes their photophysical properties, with interpretations enriched by DFT calculations. Helicenes are known to promote intersystem crossing thanks to strong spin-orbit coupling, while metals offer robust frameworks leading to a variety of molecular architectures with specific topologies together with distinct excited-state properties. The electronic configurations and energy levels of the ligand and metal orbitals thus significantly modulate the photophysical and chiroptical behaviors of these complexes. In-depth analysis of chiroptical properties, notably electronic circular dichroism and circularly polarized luminescence, emphasizes the influence of different stereogenic elements on the chiroptical responses across various energy ranges with appealing "match-mismatch" effects. Finally, we describe future prospects of helicene NHCs, particularly in the context of emerging research on cost-effective and abundant transition metals for materials science and for photocatalysis. Indeed, the inherent long-lived MLCT, excited-state delocalization, structural rigidity, and intrinsic chirality of these complexes present intriguing avenues for future investigations.

Controlling Polarization‐Induced Polaron Accumulation in OLEDs via Device Design

AbstractSpontaneous alignment of molecular electric dipole moments, known as spontaneous orientation polarization (SOP), is present in many organic electronic materials. The SOP‐induced field changes the internal voltage distribution within the device, altering polaron injection and accumulation. The important role of SOP in organic light‐emitting devices (OLEDs) has recently been emphasized with clear links between dipole alignment and device efficiency and operational lifetime. Prior work has thus sought to engineer SOP via changes in thin film composition or processing conditions. These efforts have generally been directed at the OLED electron transport layer, which can show strong SOP. This work takes a different approach, focusing instead on how changes in device architecture can be applied to tune the magnitude and dynamics of polaron accumulation in response to SOP. In this work, it is demonstrated that the introduction of SOP into the device emissive layer offers control over the spatial location of accumulation. In parallel, insertion of a spacer layer between the hole transport and emissive layers can be used to tune the polaron accumulation rate and density during device operation. Both of these architectural changes permit an increase in OLED efficiency and a pathway around the deleterious impact of SOP‐induced polaron accumulation.

Precise Regulation of the Reverse Intersystem Crossing Pathway by Hybridized Long-Short Axis Strategy for High-Performance Multi-Resonance TADF Emitters.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules have experienced great success in organic light-emitting diodes (OLEDs) owing to their outstanding quantum efficiencies and narrow full width at half-maximums (FWHMs). However, the reverse intersystem crossing (RISC) rates of MR-TADF emitters are usually small, which will lead to relatively long triplet exciton lifetime and severe efficiency roll-off. Here, we report an effective molecular design strategy to introduce multichannel RISC pathways and thus increase RISC rates without compromising the color fidelity and emission efficiency by the "hybridized long-short axis (HLSA)" strategy. The TPA-CN-BN shows a near-unity photoluminescence quantum yield, rapid RISC rate of 1.4 × 105 s-1, narrow FWHM of 23 nm, and small singlet-triplet energy gap (ΔEST) of 0.06 eV in solution. The non-sensitized OLED based on TPA-CN-BN exhibits a narrowband emission with the FWHM of 31 nm, in company with external quantum efficiency (EQE) of 37.9%. Notably, the device exhibits the low efficiency roll-off as the EQEs maintain 34.8% and 21.8% at 100 and 1000 cd m-2, respectively, representing the best performance for single-host OLEDs based on the BCzBN skeleton. This study provides a fresh and promising approach to realize high-performance OLEDs with high color purity and remarkable device efficiency.

Efficient Triplet Harvesting via Hot Exciton Utilization in Solution Processed OLEDs Employing Tetraphenyl Buta‐1,3‐Diene Based AIE Emitters

AbstractHigh photoluminescence quantum yield (PLQY) especially in solid‐state together with harvesting radiative triplet excitons are essential to achieve efficient organic light‐emitting diodes (OLEDs). Herein, the aggregation induced emission (AIE) active tetraphenyl buta‐1,3‐diene (TPB) moiety has been employed and tactfully modified to obtain orthogonally oriented donor‐acceptor (D‐A‐π‐A‐D) type derivatives (namely, TPB‐CHO‐TPA and TPB‐CN‐TPA) which possess additionally the hybridized local and charge transfer (HLCT) type excited‐state. Moreover, computational studies have revealed the possibility of triplet harvesting through hot exciton mechanism in these designed emitters. These key features along with excellent solubility in most of the organic solvents have encouraged to utilize these as light emitting materials for solution processed non‐doped and doped OLED devices. The optimal OLED device using TPB‐CHO‐TPA exhibits yellow light emission (ELmax = 572 nm and CIEx,y = 0.48, 0.51) having maximum external quantum efficiency (EQEmax) of 7.6% with power and current efficiency of 6.1 lm W−1 and 8.9 cd A−1 where the calculated exciton utilization efficiency (EUE) approaches to 97%, indicating efficient triplet harvesting in electroluminescence process. This work signifies a novel design strategy for AIE‐based HLCT type emitters having efficient hot exciton utilization which can pave the way for future development of TPB based highly efficient OLED devices.

Precise Regulation of the Reverse Intersystem Crossing Pathway by Hybridized Long‐Short Axis Strategy for High‐Performance Multi‐Resonance TADF Emitters

Multi‐resonance thermally activated delayed fluorescence (MR‐TADF) molecules have experienced great success in organic light‐emitting diodes (OLEDs) owing to their outstanding quantum efficiencies and narrow full width at half‐maximums (FWHMs). However, the reverse intersystem crossing (RISC) rates of MR‐TADF emitters are usually small, which will lead to relatively long triplet exciton lifetime and severe efficiency roll‐off. Here, we report an effective molecular design strategy to introduce multichannel RISC pathways and thus increase RISC rates without compromising the color fidelity and emission efficiency by the “hybridized long‐short axis (HLSA)” strategy. The TPA‐CN‐BN shows a near‐unity photoluminescence quantum yield, rapid RISC rate of 1.4 × 105 s‐1, narrow FWHM of 23 nm, and small singlet‐triplet energy gap (ΔEST) of 0.06 eV in solution. The non‐sensitized OLED based on TPA‐CN‐BN exhibits a narrowband emission with the FWHM of 31 nm, in company with external quantum efficiency (EQE) of 37.9%. Notably, the device exhibits the low efficiency roll‐off as the EQEs maintain 34.8% and 21.8% at 100 and 1000 cd m‐2, respectively, representing the best performance for single‐host OLEDs based on the BCzBN skeleton. This study provides a fresh and promising approach to realize high‐performance OLEDs with high color purity and remarkable device efficiency.

The Combination of a Donor-Acceptor TADF and a MR-TADF Emitting Core Results in Outstanding Electroluminescence Performance.

Here the utility and potential of an emitter design are demonstrated, consisting of a narrowband-emitting multiresonant thermally activated delayed fluorescent (MR-TADF) core that is decorated with a suitably higher energy donor-acceptor TADF moiety. Not only does this D-A TADF group offer additional channels for triplet exciton harvesting and confers faster reverse intersystem crossing (RISC) kinetics but it also acts as a steric shield, insulating the emissive MR-TADF core from aggregation-caused quenching. Two emitters, DtCzBN-CNBT1 and DtCzBN-CNBT2, demonstrate enhanced photophysical properties leading to outstanding performance of the organic light-emitting diodes (OLEDs). DtCzBN-CNBT2, containing a D-A TADF moiety, has a faster kRISC (1.1×105 s-1) and higher photoluminescence quantum yield (ΦPL: 97%) compared to DtCzBN-CNBT1 (0.2×105 s-1, ΦPL: 90%), which contains a D-A moiety that itself is not TADF. The sensitizer-free OLEDs with DtCzBN-CNBT2 achieve a record-high maximum external quantum efficiency (EQEmax) of 40.2% and showed milder efficiency roll-off (EQE1000 of 20.7%) compared to the DtCzBN-CNBT1-based devices (EQEmax of 37.1% and EQE1000 of 11.9%).

Original Blue Light-Emitting Diphenyl Sulfone Derivatives as Potential TADF Emitters for OLEDs

Organic light-emitting diodes (OLEDs) have emerged as one of the dominant technologies in displays due to their high emission efficiency and low power consumption. However, the development of blue color emitters has fallen behind that of red and green emitters, posing challenges in achieving optimal efficiency, stability, and accessibility. In this context, thermally activated delayed fluorescence (TADF) emitters hold promise as a potential solution for cost-effective, exceptionally efficient, and stable blue OLEDs due to their potential high efficiency and stability. TADF is a principle where certain organic materials can efficiently convert both singlet and triplet excitons, theoretically achieving up to 100% internal quantum efficiency. This research focused on diphenyl sulfone derivatives with carbazole groups as TADF compounds. Quantum chemical calculations and photoluminescence properties show the potential TADF properties of the molecules. New materials exhibit glass transition temperatures that would classify them as molecular glasses. Depending on the structure of the molecule, the photoluminescence emission is in the blue or green spectral region. Organic light-emitting diodes were fabricated from neat thin films of emitters by the wet casting method. The best performance in the deep blue emission region was achieved by a device with a turn-on voltage of 4 V and a maximum brightness of 178 cd/m2. In the blue-green emission region, the best performance was observed by an OLED with a turn-on voltage of 3.5 V, reaching a maximum brightness of 660 cd/m2.

Experimental and Theoretical Approaches for Detecting Latent Lateral Leakage Current of Organic Light-Emitting Diodes

Experimental and Theoretical Approaches for Detecting Latent Lateral Leakage Current of Organic Light-Emitting Diodes

Tailoring Ultra-Narrowband Tetraborylated Multiple Resonance Emitter for High-Performance Blue OLED.

Ultra-narrowband multiple resonance (MR) emitters are a key component in the fabrication of highly efficient and stable blue organic light-emitting diodes (OLEDs). To explore the theoretical boundaries of wavelength and full width at half maximum (FWHM) in blue emitters, the currently narrowest boron-based MR emitter is carefully designed by integrating the superior v-DABNA and BBCz-DB structures under the auspices of the ingenious short-range charge-transfer region regulation strategy. The target tetraboron compound TB-PB demonstrates a blue emission with an emission maximum of 473nm, a small FWHM of 12nm and a CIEy coordinate of 0.14. Benefiting from the emitter's high photoluminescence quantum yield (99%), low excited-state energy (2.74eV) and short delayed fluorescence lifetime (0.53µs), the corresponding OLED achieves exceptional efficiencies of 36.4%, 49.1cdA-1, and 51.4lmW-1 with a record-high luminescence of 9.0×105cdm-2, an ultra-narrow FWHM of 15nm and a CIEy coordinate of 0.20. These breakthroughs will accelerate the development of next-generation blue emitters and lead to the advancement of OLED technology.

A 2-D coordination polymer based on 3-(2-pyridyl)-5-(4-chlorophenyl)-1,2,4-triazine ligands and lead(II) bromide: synthesis, structure, luminescent properties, and application in organic light-emitting diodes

The combination of PbBr2 with 3-(2-pyridyl)-5-(4-chlorophenyl)-1,2,4-triazine (PCPT) results in a 2-D Pb(II) coordination polymer, denoted as [Pb9(PCPT)4Br18] n . This compound has been identified and studied through CHN analysis, FT-IR, and 1H NMR spectroscopy, in addition to detailed analysis using single-crystal X-ray diffraction techniques. Considering the primary and secondary Pb–N and Pb–Br bonds, Pb1 and Pb2 exhibit hemidirected pentagonal bipyramidal geometries, whereas Pb3, Pb4, and Pb5 demonstrate holodirected octahedral geometries. The 2-D structure transitions into a 3-D arrangement due to the presence of non-covalent C–H…Br and π…π stacking interactions. The interactions highlighted above enhance the structural stability and support the transfer of charge and energy between metal centers, positioning the polymer as a potential candidate for luminescence applications. Analysis of the electro-optical characteristics of this compound indicates its suitability as a luminescent material for incorporating into organic light-emitting diodes.

Interfacial Exciton-Polaron Quenching in Organic Light-Emitting Diodes

In organic light-emitting diodes (OLEDs), understanding the efficiency loss mechanism known as exciton-polaron quenching (EPQ) has been a longstanding challenge. Traditionally, EPQ was believed to occur mainly the bulk of the OLED emission layer (EML) due to the coexistence of polarons and excitons, limiting our understanding of its full impact. Here, we report a previously overlooked phenomenon termed “interfacial EPQ (Inf. EPQ),” which occurs at the heterointerface between the EML and the adjacent charge transport layer (CTL). We observe the transfer of EML excitons to CTL polarons across this interface, spanning distances of up to 4 nm. Notably, Inf. EPQ exceeds EPQ within the EML bulk, even in devices with a interfacial energy barrier (>0.2 eV). We propose a methodology that enables independent probing of Inf. EPQ, systematic validation of its essential parameters, and the identification of Dexter energy transfer as its governing mechanism. Importantly, our findings highlight Inf. EPQ as a phenomenon across devices with various luminescent mechanisms, wavelengths, and injection levels. By effectively addressing Inf. EPQ, we achieve efficiency enhancements in red, green, and blue phosphorescent OLEDs, by 70%±8%, 47%±5%, and 66%±6%, respectively. Our work advances the physical understanding of exciton and polaron dynamics at organic heterointerfaces, providing applicable solutions to Inf. EPQ-related issues in practical devices. Published by the American Physical Society 2024

Optical, Photophysical, and Electroemission Characterization of Blue Emissive Polymers as Active Layer for OLEDs.

Polymers containing π-conjugated segments are a diverse group of large molecules with semiconducting and emissive properties, with strong potential for use as active layers in Organic Light-Emitting Diodes (OLEDs). Stable blue-emitting materials, which are utilized as emissive layers in solution-processed OLED devices, are essential for their commercialization. Achieving balanced charge injection is challenging due to the wide bandgap between the HOMO and LUMO energy levels. This study examines the optical and photophysical characteristics of blue-emitting polymers to contribute to the understanding of the fundamental mechanisms of color purity and its stability during the operation of OLED devices. The investigated materials are a novel synthesized lab scale polymer, namely poly[(2,7-di(p-acetoxystyryl)-9-(2-ethylhexyl)-9H-carbazole-4,4'-diphenylsulfone)-co-poly(2,6-diphenylpyrydine-4,4'-diphenylsulfone] (CzCop), as well as three commercially supplied materials, namely Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), poly[9,9-bis(2'-ethylhexyl) fluorene-2,7-diyl] (PBEHF), and poly (9,9-n-dihexyl-2,7-fluorene-alt-9-phenyl-3,6-carbazole) (F6PC). The materials were compared to evaluate their properties using Spectroscopic Ellipsometry, Photoluminescence, and Atomic Force Microscopy (AFM). Additionally, the electrical characteristics of the OLED devices were investigated, as well as the stability of the electroluminescence emission spectrum during the device's operation. Finally, the determined optical properties, combined with their photo- and electro-emission characteristics, provided significant insights into the color stability and selectivity of each material.

Suppression of Initial Degradation via an Interfacial Charge-Induced Overshooting Effect in Solution-Processed Organic Light-Emitting Diodes.

As the chemical stability of organic materials in organic light-emitting diodes (OLEDs) greatly impacts devices' lifetime, a thoughtful and advanced design of materials and device structures is necessary. In our work, we have achieved lifetime enhancement at its initial stage for solution-processed OLEDs. This improvement was realized through the implementation of a double electron transporting layer (dETL) composed of 2-[4-(9,10-dinaphthalen-2-yl-anthracen-2-yl)-phenyl]-1-phenyl-1H-benzoimidazole (ET) and hydroxyquinolinolato-lithium (Liq). A giant surface potential was generated at the surface of a constituent electron transport layer (ETL) that contained a higher concentration of Liq with high polarity. This giant surface potential simultaneously promoted the injection of trapped/accumulated electrons through the interface within dETL and the injection of holes from the anode, generating more exciton recombination events and ultimately enhancing efficiency by 133.0% and lifetime LT95 (luminance dropped by 5%) by 300% with an overshooting effect. Additionally, the degradation at the emitting layer was mitigated by shifting the degradation zone to the dETL, which was evidenced by laser desorption/ionization-time-of-flight (LDI-TOF) mass spectroscopy.

Improved Charge Recombination Efficiency in Organic Light‐Emitting Transistors via Luminescent Radicals

AbstractLuminescent radicals are attracting attention as emitters in electroluminescent devices thanks to the exploitation of doublet excitons. Recent studies reveal that exciton formation in radical organic light‐emitting diodes (OLEDs) primarily occurs through a charge trapping mechanism. Although typically detrimental for OLEDs, this might be a key process to elucidate light emission in organic light‐emitting transistors (OLETs). Here, a unipolar n‐type architecture suitable for the implementation of radical emitters is introduced, designed based on computational calculations. The operation of the as‐realized devices incorporating the newly synthesized [2,6‐dichloro‐4‐(2,6‐dimethoxyphenyl)phenyl](3,5‐dichloro‐4‐pyridyl) (2,4,6‐trichlorophenyl)methyl radical is investigated via transient electroluminescence measurements to demonstrate the occurrence of long‐living emission ascribed to the charge trapping mechanisms. Moreover, a comprehensive understanding of the processes governing radical‐OLET is obtained by recording complete 2D maps of both optical and electrical response of the device as a function of applied voltages. Notably, the trapping of electrons by radical moieties is demonstrated to generate a negative charge density in the emissive layer that facilitates holes to be injected: increasing the balance of opposite charge carriers, a tenfold enhancement of the external quantum efficiency (EQE) at the proper source‐drain and source‐gate voltage conditions is reported to reach a maximum EQE value of 0.2%.

π‐Extended Phenoxazine‐Based Asymmetric MR‐TADF Emitters for Narrow Emission Band Green OLEDs with a Power Efficiency of 150 lm W−1, an EQE of 27%, and an LT95 of Over 3000 h at 1000 cdm−2

AbstractAlthough multi‐resonance thermally activated delayed fluorescent (MR‐TADF) emitters simultaneously achieve high color purity and high efficiency in organic light‐emitting devices (OLEDs), MR‐TADF‐based OLEDs suffer from severe efficiency roll‐off and lifetime issues for practical application. To overcome these issues, a key solution is hyper OLED technology sensitized by TADF or phosphorescent emitters. In this study, a series of π‐extended phenoxazine‐based asymmetric MR‐TADF emitters for long lifetime, low‐power consumption, and narrow emission band green OLEDs is developed. As a sensitizer, a well‐known phosphorescent emitter is used, fac‐tris(2‐phenylpyridinato‐C2,N)iridium(III) [Ir(ppy)3]. Consequently, these MR‐TADF emitters achieve hyper OLEDs with a power efficiency of 150 lm W−1, an external quantum efficiency of 27%, and a long lifetime LT95 of over 3000 h at high brightness of 1000 cdm−2. These performances are among the best in scientific literature.

Diffusion‐Free Intramolecular Triplet–Triplet Annihilation Contributes to the Enhanced Exciton Utilization in OLEDs

AbstractTriplet–triplet annihilation (TTA), or triplet fusion, is a biexcitonic process in which two triplet‐excited molecules can combine their energy to promote one into an excited singlet state. To alleviate the dependence of the TTA rate and yield on triplet diffusion in both solid and solution environments, intramolecular TTA (intra‐TTA) has been recently proposed in conjugated molecular systems able to hold multiple triplet excitons simultaneously. Developing from the previous demonstration of TTA performance enhancement in sensitized upconversion solutions, here similar improvements in triplet harvesting in solid‐state films are reported under electrical excitation in organic light emitting diodes (OLEDs). At low dye concentration and low current densities, the intra‐TTA active OLED shows a +40% improved external quantum efficiency with respect to the reference device, and a TTA spin‐statistical factor f 4DPA of 0.4, close to that determined in fluid solution for the individual chromophore (0.45). These results therefore indicate the utility of this molecular design strategy across a wider range of TTA applications, and with particular utility in the further development of low‐power TTA‐enhanced OLEDs.

Quantitative structure-property relationship of glass transition temperatures for organic compounds

The glass transition temperatures (T gs) of materials used in the manufacture of organic light-emitting diodes (OLEDs) determine their thermal stability. Three Dragon descriptors, TPC, RBF and TDB04s, were adopted to develop quantitative structure-property relationships (QSPR) for the prediction of the T gs of 66 compounds (Data Set I) for OLED application, by applying random forest (RF) and support vector machine (SVM). The RF Model A, based on a training set (44 compounds), was validated with a test set (22 compounds). The RF Model A possesses a coefficient of determination R 2 of 0.942 and a root mean square (rms) error of 10.750 K for the training set and R 2 of 0.909 and rms error of 11.102 K for the test set, which are more accurate than the results from the SVM model. The RF Model A was further validated with 63 OLED molecules (Data Set II). Moreover, the three Dragon descriptors (TPC, RBF and TDB04s) were used to build another T g QSPR model (named RF Model B) for a large dataset of 1934 OLED molecules (Data Set III), which achieved rms errors of 16.79 K for Data Set III, 22.89 K for Data Set I and 20.17 K for Data Set II.

Lithosphere infiltrometer: A low cost, automated infiltrometer (permeameter) for measurement of soil health, infiltration, and hydraulic conductivity

Accurate measurement of infiltration rate and hydraulic conductivity is important for assessing soil physical health, irrigation management and catchment modelling. Commercially available infiltrometers are often expensive, fragile, and require specialist knowledge to operate and perform complex post-measurement calculations. We developed the Lithosphere Infiltrometer (permeameter) to be usable for both experienced soil researchers, and users without prior technical or scientific expertise in soil science. The Lithosphere Infiltrometer is able measure both surface and subsoil infiltration rate and hydraulic conductivity. It is manufactured using 3D-printed parts and off-the-shelf electronic components. It has a robust, quad-leg design that allows for rapid leveling of the device and accurate setting of water depth via a novel 3D-printed bell chamber. The water level is measured using a U85 JRT laser with ±1 mm accuracy connected to an Adafruit Huzzah 32 microcontroller. Infiltration rate and hydraulic conductivity are calculated at 1 to 10 min time steps, and data is presented in real-time on an OLED display. Data is stored on the device and available for download to a mobile device by Wi-Fi.

Research Progress of Deep-Red to Near-Infrared Electroluminescent Materials Based on Organic Cyclometallated Platinum(II) Complexes.

In recent years, the near-infrared (NIR) light-emitting materials have attracted increasing attention due to the broad application prospects in the fields of military industry, aerospace, lighting, display and wearable devices. As the transition metal complexes, platinum(II) complexes have been shown to emit luminescence efficiently in NIR organic light-emitting diodes because of the unique d8 electron structure. This structure ensures that the platinum(II) complex molecules exhibit a high planarity, variety of excited states, and strong intermolecular interactions. This review summarizes the research progress of deep red to NIR organic light-emitting materials based on platinum(II) complexes in recent years and provides a certain reference for the further design and synthesis of NIR platinum(II) complex luminescent materials with superior performance.

High-Performance Multicolor Organic Light-Emitting Diodes Based on a Pt(II) Carbene Complex Featuring Hemiligand Interaction.

Utilizing a single organic light-emitting diode (OLED) architecture for multicolor emissions can significantly simplify manufacturing progress and broaden applications. Here, we report on a carbene-based Pt(II) complex, designated as Pt(pyiOppy), which exhibits an unusual dimeric packing mode solely by hemiligand π···π stacking. This feature is distinct from the well-known Pt···Pt or Pt···ligand interactions. The dimer persists in new types of orbital combinations, along with its triplet transition state, which are evidenced for the first time. Pt(pyiOppy), under various doping concentrations in a solid matrix, demonstrates multicolor emissions ranging from green to red, all exhibiting high photoluminescent quantum efficiencies (48-97%). The devices incorporating Pt(pyiOppy) can emit green, yellow, orange, and red lights, covering a CIE coordinate range of (0.28-0.65, 0.61-0.34). All the devices also achieve appreciable maximum external quantum efficiencies (9.4-17.2%) and impressive lifetimes of hundreds of hours (LT70 at 1000 cd/m2). These findings showcase a new type of Pt(II) aggregate enabling well-controlled, multicolor high-performance phosphorescent OLEDs.