Maximum External Quantum Efficiency Research Articles

Enhancing the Performance of Perovskite Light-Emitting Diodes via Synergistic Effect of Defect Passivation and Dielectric Screening

HighlightsSynergistic passivation mechanism of the dual functional compound of potassium bromide for metal halide perovskite films, that is through chemical bonding and physical screening towards the various types of defects.Metal-ion additives can simultaneously passivate the defects of halide vacancies with bromine anions and dangling bond defects with metal cations.Achieve the maximum external quantum efficiency of ~21% and maximum luminance of ~60,000 cd m−2.

Self-powered stable high-performance UV–Vis–NIR broadband photodetector based on PVP-Cobalt@Carbon nanofibers/n-GaAs heterojunction

The self-powered PVP-Co@C nanofibers/n-GaAs heterojunction photodetector (HJPD) was fabricated by electrospinning of the nanofibers onto GaAs. An excellent rectification ratio of 6.60 × 106 was obtained from I–V measurements of the device in the dark. The I–V measurements of the fabricated device under 365 nm, 395 nm and 850 nm lights, as well as I–V measurements in visible light depending on the light intensity, were performed. The HJPD demonstrated excellent photodetection performance in terms of a good responsivity of ∼225 mA W−1 (at −1.72 V) and at zero bias, an impressive detectivity of 6.28 × 1012 Jones, and a high on/off ratio of 8.38 × 105, all at 365 nm wavelength. In addition, the maximum external quantum efficiency and NPDR values were 3495% (V = −1.72 V) and 2.60 × 1010 W−1 (V = 0.0 V), respectively, while the minimum NEP value was ∼10−14 W.Hz−1/2 for 365 nm at V = 0.V volts. The HJPD also exhibited good long-term stability in air after 30 d without any encapsulation.

Efficient, Color-Stable, Pure-Blue Light-Emitting Diodes Based on Aromatic Ligand-Engineered Perovskite Nanoplatelets.

Perovskite nanoplatelets (NPLs) show great potential for high-color-purity light-emitting diodes (LEDs) due to their narrow line width and high exciton binding energy. However, the performance of perovskite NPL LEDs lags far behind perovskite quantum dot-/film-based LEDs, owing to their material instability and poor carrier transport. Here, we achieved efficient and stable pure blue-emitting CsPbBr3 NPLs with outstanding optical and electrical properties by using an aromatic ligand, 4-bromothiophene-2-carboxaldehyde (BTC). The BTC ligands with thiophene groups can guide two-dimensional growth and inhibit out-of-plane ripening of CsPbBr3 NPLs, which, meanwhile, increases their structural stability via strongly interacting with PbBr64- octahedra. Moreover, aromatic structures with delocalized π-bonds facilitate charge transport, diminish band tail states, and suppress Auger processes in CsPbBr3 NPLs. Consequently, the LEDs demonstrate efficient and color-stable blue emissions at 465 nm with a narrow emission line width of 17 nm and a maximum external quantum efficiency (EQE) of 5.4%, representing the state-of-the-art CsPbBr3 NPL LEDs.

Excited-State Engineering Enables Efficient Deep-Blue Light-Emitting Diodes Exhibiting BT.2020 Color Gamut.

Organic luminescent materials that exhibit thermally activated delayed fluorescence (TADF) can convert non-emissive triplet excitons into emissive singlet states through a reverse intersystem crossing (RISC) process. Therefore, they have tremendous potential for applications in organic light-emitting diodes (OLEDs). However, with the development of ultra-high definition 4K/8K display technologies, designing efficient deep-blue TADF materials to achieve the Commission Internationale de l'Éclairage (CIE) coordinates fulfilling BT.2020 remains a significant challenge. Here, an effective approach is proposed to design deep-blue TADF molecules based on hybrid long- and short-range charge-transfer by incorporation of multiple donor moieties into organoboron multiple resonance acceptors. The resulting TADF molecule exhibits deep-blue emission at 414nm with a full width at half maximum (FWHM) of 29nm, together with a thousand-fold increase in RISC rate. OLEDs based on the champion material achieve a record maximum external quantum efficiency (EQE) of 22.8% with CIE coordinates of (0.163, 0.046), approaching the coordinates of the BT.2020 blue standard. Moreover, TADF-assisted fluorescence devices employing the designed material as a sensitizer exhibit an exceptional EQE of 33.1%. This work thus provides a blueprint for future development of efficient deep-blue TADF emitters, representing an important milestone towards meeting the blue color gamut standard of BT.2020.

Rational Design of Coumarin-Based Hybridized Local and Charge-Transfer Blue Emitters for Solution-Processed Organic Light-Emitting Diodes.

Hybridized local and charge-transfer (HLCT) with the utilization of both singlet and triplet excitons through the "hot excitons" channel have great application potential in highly efficient blue organic light-emitting diodes (OLEDs). The proportion of charge-transfer (CT) and locally excited (LE) components in the relevant singlet and triplet states makes a big difference for the high-lying reverse intersystem crossing process. Herein, three novel donor (D)-acceptor (A) type HLCT materials, 7-([1,1'-biphenyl]-4-yl(9,9-dimethyl-9H-fluoren-2-yl)amino)-3-phenyl-1H-isochromen-1-one (pPh-7P), 7-([1,1'-biphenyl]-4-yl(9,9-dimethyl-9H-fluoren-2-yl)amino)-3-methyl-1H-isochromen-1-one (pPh-7M), and 6-([1,1'-biphenyl]-4-yl(9,9-dimethyl-9H-fluoren-2-yl)amino)-3-methyl-1H-isochromen-1-one (pPh-6M), were rationally designed and synthesized with diphenylamine derivative as donor and oxygen heterocyclic coumarin moiety as acceptors. The proportions of CT and LE components were fine controlled by changing the connection site of diphenylamine derivative at C6/C7-position and the substituent at C3-position of coumarin moiety. The HLCT characteristics of pPh-7P, pPh-7M, and pPh-6M were systematically demonstrated through photophysical properties and density functional theory calculations. The solution-processed doped OLEDs based on pPh-6M exhibited deep-blue electroluminescence with the maximum emission wavelength of 446 nm, maximum luminance of 8755 cd m-2, maximum current efficiency of 5.83 cd A-1, and maximum external quantum efficiency of 6.54 %. The results reveal that pPh-6M with dominant 1LE and 3CT components has better OLED performance.

Achieving Record External Quantum Efficiency of 11.5 % in Solution-Processable Deep-Blue Organic Light-Emitting Diodes Utilizing Hot Exciton Mechanism.

High performance solution-processable deep-blue emitters with a Commission International de l'Eclairage (CIE) coordinate of CIEy≤0.08 are highly desired in ultrahigh-definition display. Although, deep-blue materials with hybridized local and charge-transfer (HLCT) excited-state feature are promising candidates, their rigidity and planar molecular structures limit their application in solution-processing technique. Herein, four novel deep-blue solution-processable HLCT emitters were first proposed by attaching rigid imide aliphatic rings as functional units onto the HLCT emitting core. The functional units not only improve solubility, enhance thermal properties and morphological stability of the emitting core, but also promote photoluminescence efficiency, balance charge carrier transport, and inhibit aggregation-caused quenching effect due to the weak electron-withdrawing property as well as steric hindrance. The corresponding solution-processable organic light-emitting diodes (OLEDs) substantiate an unprecedented maximum external quantum efficiency (EQEmax) of 11.5 % with an emission peak at 456 nm and excellent colour purity (full width at half maximum=56 nm and CIEy=0.09). These efficiencies represent the state-of-the-art device performance among the solution-processable blue OLEDs based on the "hot exciton" mechanism. This simple strategy opens up a new avenue for designing highly efficient solution-processable deep-blue organic luminescent materials.

Achieving Record External Quantum Efficiency of 11.5 % in Solution‐Processable Deep‐Blue Organic Light‐Emitting Diodes Utilizing Hot Exciton Mechanism

AbstractHigh performance solution‐processable deep‐blue emitters with a Commission International de l′Eclairage (CIE) coordinate of CIEy≤0.08 are highly desired in ultrahigh‐definition display. Although, deep‐blue materials with hybridized local and charge‐transfer (HLCT) excited‐state feature are promising candidates, their rigidity and planar molecular structures limit their application in solution‐processing technique. Herein, four novel deep‐blue solution‐processable HLCT emitters were first proposed by attaching rigid imide aliphatic rings as functional units onto the HLCT emitting core. The functional units not only improve solubility, enhance thermal properties and morphological stability of the emitting core, but also promote photoluminescence efficiency, balance charge carrier transport, and inhibit aggregation‐caused quenching effect due to the weak electron‐withdrawing property as well as steric hindrance. The corresponding solution‐processable organic light‐emitting diodes (OLEDs) substantiate an unprecedented maximum external quantum efficiency (EQEmax) of 11.5 % with an emission peak at 456 nm and excellent colour purity (full width at half maximum=56 nm and CIEy=0.09). These efficiencies represent the state‐of‐the‐art device performance among the solution‐processable blue OLEDs based on the “hot exciton” mechanism. This simple strategy opens up a new avenue for designing highly efficient solution‐processable deep‐blue organic luminescent materials.

High performance Al/WSe2/CuO/ITO structure based broadband photodetector

This letter reports a Al/WSe2/CuO/ITO structure based broadband photodetector. The low cost spin coating technique is utilized to deposit, p-type WSe2 film and n-type CuO film. The Al contacts were deposited over WSe2 film using thermal evaporation unit. The suggested photodetector gives the broad photo response with maximum Responsivity RS (A/W) and External Quantum Efficiency (EQE) value of 3099 A/W, 3680 A/W, and 493 A/W; 1.20 × 106%, 1.52× 106% and 2.04 × 105% at 350 nm (UV), 500 nm (visible) and 950 nm (IR) under application of −2 V bias. The EQE value beyond 100% are attributed to trap assisted photomultiplication mechanism.

Surface Treatment with Tailored π-Conjugated Fluorene Derivatives Significantly Enhances the Performance of Perovskite Light-Emitting Diodes.

Surface defect passivation and carrier injection regulation have emerged as effective strategies for enhancing the performance of perovskite light-emitting diodes (Pero-LEDs). It usually requires two functional molecules to realize defect passivation and carrier injection regulation separately. In other words, developing one single molecule possessing these capabilities remains challenging. Herein, we utilized π-conjugated fluorene derivatives as surface treatment materials, 9,9-Spirobi[fluorene] (SBF), 9,9-Spirobifluoren-2-yl-diphenylphosphine oxide (SPPO1), and 2,7-bis(diphenylphosphoryl)-9,9'-spirobifluorene (SPPO13), to investigate the influence of their chemical structure on device optoelectronic performance, especially for defect passivation and carrier injection regulation. Consequently, the passivation capability of double-bonded SPPO13 surpassed single-bonded SPPO1 and nonbonded SBF, which all showed excellent electron transport properties, enhancing electron injection. The maximum external quantum efficiencies (EQE) for Pero-LEDs treated with SBF, SPPO1, and SPPO13 were 8.13, 17.48, and 22.10%, respectively, exceeding that of the derivative-free device (6.55%). Notably, SPPO13-treated devices exhibited exceptional reproducibility, yielding an average EQE of 20.00 ± 1.10% based on 30 devices. This result emphasizes the potential of tailored fluorene derivatives for enhancing the device performance of Pero-LEDs.

Structurally Tunable Donor-Bridge-Fluorophore Architecture Enables Highly Efficient and Concentration-Independent Narrowband Electroluminescence.

Luminescent materials with narrowband emission have extraordinary significance for developing ultrahigh-definition display. B-N-containing multiple resonance thermally activated delayed fluorescence (MR-TADF) materials are strong contenders. However, their device performances pervasively encounter detrimental aggregation-caused quenching effect that is highly vulnerable to doping concentration, complicating device fabrication. Therefore, constructing highly efficient and concentration-independent MR-TADF emitters is of pragmatic importance for improving device controllability and reproducibility, simplifying manufacturing procedures, and conserving production costs. Here, by systematic arrangement of donor triphenylamine and fluorophore BNCz on distinct bridges, a spatial confinement strategy has been developed with a donor-bridge-fluorophore architecture. Structurally fine modulation and progressive evolution to construct molecular entities with congested steric hindrance effect that can suppress intermolecular interactions without substantially affecting the luminescence tone of fluorophore BNCz, resulting in highly efficient and concentration-independent narrowband emitters; through isomer engineering, two isomers BN-PCz-TPA and TPA-PCz-BN with different crystal stacking patterns are synthesized by altering the connection mode between triphenylamine and BNCz. As a result, BN-PCz-TPA-based device showcases maximum external quantum efficiency (EQE) of 36.3% with narrow full-width at half-maximum of 27 nm at 10 wt% doping concentration. Even at 20 wt% doping concentration, the maximum EQE remains at 32.5% and the emission spectrum is almost unchanged.

High‐Efficiency and Long‐Lifetime Near‐Infrared OLEDs Based on Iridium Complexes with Enhanced Horizontal Emitting Dipole Orientation

AbstractHigh‐efficiency and long‐lifetime near‐infrared (NIR) organic light‐emitting diodes (OLEDs) are rarely reported. Herein, three efficient NIR Ir(III) complexes 1–3 are developed with specially designed cyclometallated ligands based on pyrido[3,4‐b]pyrazine and oriented substitutions along the Ir─N bond axis. Electron‐deficient pyrazine ring effectively stabilizes LUMO energy, leading to significant emission bathochromic shift. Importantly, for complexes 2 and 3, oriented substitutions along the direction of the Ir─N bond axis considerably enhance the horizontal emitting dipole orientation ratio up to 90%. Their OLEDs demonstrate high maximum external quantum efficiencies (EQEs), negligible efficiency roll‐offs, superior radiance, and long lifetimes. The maximum EQEs and radiances of devices are 9.84% and 158 W Sr−1 m−2 at 725 nm for 1, 6.98% and 14.03 W Sr−1 m−2 at 760 nm for 2, and 12.49% and 18.94 W Sr−1 m−2 at 735 nm for 3, respectively. The device lifetime LT97 at 10 mA cm−2 is 453 h for complex 2, which sets a champion lifetime for NIR‐OLEDs. This work demonstrates that pyrido[3,4‐b]pyrazine is a desired building block for robust NIR emitting Ir(III) complexes, providing a superior paradigm to combine high efficiency, negligible roll‐off, and long device lifetime simultaneously toward practical applications.

Well-type thick-shell quantum dots combined with double hole transport layers device structure assisted realization of high-performance quantum dot light-emitting diodes

Quantum dot (QD) light-emitting diodes (QLEDs) are promising for next-generation lighting and displays. Considering the optimization design of both the QD and device structure is expected to improve the QLED's performance significantly but has rarely been reported. Here, we use the thick-shell QDs combined with a dual-hole transport layer device structure to construct a high-efficiency QLED. The optimized thick-shell QDs with CdS/CdSe/CdS/ZnS seed/spherical quantum well/shell/shell geometry exhibit a high photoluminescence quantum yield of 96% at a shell thickness of 5.9 nm. The intermediate emissive CdSe layer with coherent strain ensures defect-free growth of the thick CdS and ZnS outer shells. Based on the orthogonal solvents assisted Poly-TPD&PVK dual-hole transport layer device architecture, the champion QLED achieved a maximum external quantum efficiency of 22.5% and a maximum luminance of 259955 cd m-2, which are 1.6 and 3.7 times that of thin-shell QDs based devices with single hole transport layer, respectively. Our study provides a feasible idea for further improving the performance of QLED devices.

Introducing Internal Host Component to Thermally Activated Delayed Fluorescence Emitter for Efficient NIR Nondoped Organic Light-Emitting Diodes.

Developing thermally activated delayed fluorescence (TADF) near-infrared (NIR) organic light-emitting diodes (OLEDs) based on nondoped emitting layers is intriguing yet challenging, limited by low exciton utilization and notorious concentration quenching. Herein, a facile strategy is proposed to address this issue by incorporating an internal host component onto a traditional donor (D)-acceptor (A)-type red TADF molecule. A proof-of-concept emitter with an internal host is accordingly developed as well as a control one without an internal host. In the case of their monomer states, both emitters exhibit similar emission spectra due to their identical D-A pairs. However, under nondoped conditions, significant improvement in exciton utilization and quenching-resistant features are observed for the molecule with the internal host. The corresponding nondoped OLED yielded a maximum external quantum efficiency of 2.4%, with NIR emission peaking at 765 nm, which was a nearly 10-fold improvement relative to the efficiency based on the control molecule without an internal host. To the best of our knowledge, this result is on par with those of state-of-the art nondoped NIR TADF OLEDs in a similar emission region. These results offer a feasible pathway for the design and development of high-efficiency NIR nondoped OLEDs.

Efficient Perovskite Nanograin Light-Emitting Diodes in Green-to-Blue Gamut with Co-Additive Engineering.

Perovskite nanograins exceeding the Bohr exciton diameter show great potential for high-performance light-emitting diodes (LEDs) owing to their bandgap homogeneity, spatial charge confinement, and nonlocal interaction. However, it is challenging to directly synthesize proper nanograins along with reduced crystal defects on functional substrate, and the corresponding high-efficiency perovskite LEDs (PeLEDs) have rarely been reported. In this study, crystallization modulation for perovskites with an effective co-additive system, including lithium bromide, p-fluorophenethylammonium bromide, and 18-crown-6, is performed. Furthermore, it is demonstrated that the proposed co-additive system can synergistically retard perovskite crystallization and reduce crystal defects. Consequently, high-quality perovskite nanograin solids (≈22.8nm) are obtained with a high photoluminescence quantum yield (≈88%). These superior optical properties contribute to developing efficient green PeLEDs with a champion external quantum efficiency (EQE) of 28.4% and an average EQE of 27.1%. The co-additive system can be universally applied to mixed-halide perovskite nanograin LED, presenting a maximum EQE of 24.4%, 21.6%, 17.5%, and 11.1% for the blue device at 496, 488, 478, and 472nm, respectively, along with a narrow spectral linewidth (17-14nm) and stable color. These results supplement the research on high-efficiency perovskite nanograin LEDs for multicolor displays and lighting.

Fine tuning of excited states by trifluoromethylphenyl for blue-shifted color and enhanced EQEs in thermally activated delayed fluorescence emitters

3,6-di-tert-butyl-9H-carbazole and 3,6-diphenyl-9H-carbazole have been widely used to construct blue thermally activated delayed fluorescence (TADF) emitters. However, it is difficult for related emitters to achieve maximum external quantum efficiency (EQEmax) above 20 % with the Commission Internationale de l'Eclairage (CIE) y ≤ 0.12. A new type of donor was developed to construct blue TADF molecules, namely CF3P-BuCz-TRZ and CF3P-PhCz-TRZ. The weak electron-withdrawing trifluoromethylphenyl (CF3P) with moderate steric hindrance was introduced into the 1-site of carbazole donor for improving the color purity for blue TADF emitters. More importantly, the introduction of CF3P tightly compacts the energy levels for the significant excited states in RISC process. The energy gap between the lowest singlet excited (S1) state and the lowest triplet (T1) state (Δ E(S1−T1)), as well as between T1 and the higher triplet (Tn, n ≥ 2) states (Δ E(Tn−T1)) were reduced, so that Tn (n ≥ 2) could be effectively harvested to further promote reverse intersystem crossing (RISC). As a result, the OLEDs based on CF3P-BuCz-TRZ and CF3P-PhCz-TRZ displayed blue electroluminescence with CIE coordinates of (0.156, 0.107) and (0.155, 0.115). In particular, the maximum EQEs of the CF3P-PhCz-TRZ device reached 20.43 % without employing any light out-coupling enhancement or TADF-sensitized structure. This strategy should be valuable for designing more pure-blue and deep-blue TADF emitters.

226 nm Far‐Ultraviolet‐C Light Emitting Diodes with an Emission Power over 2 mW

Far‐ultraviolet‐C (far‐UVC) light emitting diodes (LED) emitting at an emission wavelength of 226 nm with different n‐AlGaN contact layers, quantum well barriers, and quantum well numbers are compared regarding their emission power, operation voltage, and lifetime. Electroluminescence measurements show higher emission power but also an increased operation voltage with increasing Al mole fraction in the n‐AlGaN contact layer. Furthermore, it is found that both the mean emission power and the device lifetime decrease with increasing Al mole fraction (82–89%) of the quantum well barriers and therefore with increasing barrier height. Finally, 226 nm LEDs with 6 and 9 quantum wells are compared. It is observed that the sample with 9 quantum wells shows an around 30% lower mean emission power but, in contrast, the L70 lifetime of these LEDs is higher by a factor of around five. Based on these optimizations, 226 nm LEDs with a maximum external quantum efficiency of 0.28% (wall plug efficiency of 0.18%) as well as an emission power of 2.1 mW and an operation voltage of 9.6 V at 200 mA are realized.

Exciplex-driven blue OLEDs: unlocking multifunctionality applications

We present the development of multifunctional blue-emission organic light-emitting diodes (OLEDs) using TADF-exciplex materials. These OLEDs exhibit sensitivity to external stimuli and achieve a maximum external quantum efficiency (EQE) of 11.6% through partly liquid processing. This technique allows for large-scale production on arbitrary geometries.The potential multifunctionality of the devices arises from their response to low external magnetic fields (up to 100 mT) with an efficiency up to 2.5% for magnetoconductance, while maximum magneto-electroluminescence effects of 4.1% were detected. We investigated novel aspects, including the utilization of two organic materials without further doping and the investigation of the impact of 2,2ʹ,2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) processing in liquid and vapor form. The insights gained provide a fundamental understanding regarding the applicability of exciplex (EX) materials for fully solution-processed OLEDs through a deliberate omission of doping. Our work represents a significant advancement on the path towards multifunctional OLED technology, with potential applications in cost-efficient, scalable organic full-color displays and advanced sensing system.

Achieving Deep‐Blue Through‐Space Charge‐Transfer Emitter by Designing the Donor‐π‐Donor‐σ‐Acceptor Molecular Structure

AbstractIn the realm of organic light‐emitting diode (OLED), through‐space charge transfer (TSCT) thermally activated delayed fluorescence (TADF) emitters have demonstrated remarkable achievements. Nevertheless, realizing both deep‐blue emission and high efficiency by the TSCT strategy remains a persistent challenge. Here, the novel donor‐π‐donor‐σ‐acceptor (D‐π‐D‐σ‐A) type deep‐blue TSCT emitter, namely D‐tCz‐BO, is formulated to investigate its performance in OLED. D‐tCz‐BO show a narrow deep‐blue emission and efficient TADF character (λPL = 448, FWHM = 54 nm, ΦPL = 82%, and ΔEST = 0.09 eV). More importantly, the OLED based on D‐tCz‐BO as the emitter showed a maximum external quantum efficiency (EQEmax) of 20.5%, with a Commission Internationale de l'Eclairage (CIE) coordinate of (0.14, 0.12). This represents one of the best deep‐blue TSCT‐TADF emitters to date.

Highly efficient inverted organic light-emitting devices by tuning particle size of ZnO nanoparticles

Inverted organic light-emitting devices (OLEDs) have been extensively researched because they can provide many advantages such as low driving voltage and high environmental stability in display applications. However, the electron injection is a critical issue in the inverted OLEDs because the work function of the ITO cathode is too high to inject electrons from the cathode into the adjacent organic layer. In this paper, we enhanced the electron injection by tuning the particle size of ZnO nanoparticles (NPs). Hexagonal wurtzite ZnO NPs with different size were synthesized by the solution precipitation method. As the particle size increases, the photoluminescence spectrum in the visible region shifts to the long wavelength due to the narrowing of band gap. The electrical resistivity decreases with increasing the particle size. The inverted phosphorescent OLEDs with a tris(2-phenylpyridine)iridium(III) emitter have been fabricated using ZnO NPs with different size. As the particle size increases from 3.0 to 6.2 nm, the enhanced injection of electrons from the ZnO NPs to the organic electron transport layer results in the decrease of the driving voltage and the increase of the maximum external quantum efficiency (EQE). The maximum EQE of 26.02 % was achieved in the inverted OLEDs with 6.2 nm ZnO NPs.

Narrow-emitting pyridoimidazole functionalized N-heterocyclic carbene based tetradentate Pt(II) complexes for blue phosphorescent organic light-emitting diodes

Two novel classes of N-heterocyclic carbene (NHC) based tetradentate Pt(II) complexes possessing bulky benzyl groups and pyridoimidazole ligands were designed and synthesized to produce efficient blue phosphorescent organic light-emitting diodes (PHOLEDs). Two blue Pt(II) complexes are reported, namely, platinum (II) [2-(3-(1-(4-(tert-butyl)benzyl)-1H-imidazo [4,5-b]pyridin-3(2H)-yl)phenoxy)-9-(pyridin-2-yl)-9H-carbazole] (Pt(t-BuBnOCzPy)) and platinum (II) [3-(3-(1-benzyl-1H-imidazo [4,5-b]pyridin-3(2H)-yl)phenoxy)-9-(4-(tert-butyl)pyridin-2-yl)-9H-carbazole] (Pt(BnOCz4t-BuPy)), respectively. Notably, pyridoimidazole and bulky benzyl groups efficiently reduced steric hindrance, vibrational peaks, and intermolecular interactions. The photophysical and electrochemical properties of the two Pt(II) complexes were analytically examined experimentally and theoretically. The complexes exhibited blue electroluminescence (EL) emission at 466 nm with a small full-width half maximum (FWHM) of 26 nm and completely suppressed vibrational emission peaks. Blue PHOLEDs, at 5 wt% Pt(t-BuBnOCzPy) and Pt(BnOCz4t-BuPy) doping ratios exhibited maximum external quantum efficiencies (EQEmax) of 19 and 18.6 %, maximum power efficiencies (PEmax) of 25.5 and 24.9 cd m−2, and maximum current efficiencies (CEmax) of 24.3 and 24.3 cd m−2 with Commission International de I'Eclairage (CIEx,y) color coordinates of (0.13, 0.17) and (0.13, 0.17), respectively. These superior results suggest that the designed benzylated NHC pyridoimidazole tetradentate Pt(II) complexes provide a novel means of reducing steric hindrance and intermolecular interactions.