Efficiency Roll-off Research Articles

Dielectric Regulation for Efficient Top-Emission Perovskite Light-Emitting Diodes with Suppressed Efficiency Roll-off.

Perovskite light-emitting diodes (PeLEDs) have shown incalculable application potential in the fields of next-generation displays and light communication owing to the rapidly increased external quantum efficiencies (EQEs). However, most PeLEDs obtain a maximum EQE at small current density (J) region and suffer from severe efficiency roll-off in different extents. Herein, it is demonstrated that the dopant with large dipole moment like KBF4 facilitates the effective dielectric regulation of perovskite emissive layer. The increased dielectric constant lowers the exciton binding energy and suppresses the Auger recombination of the 2D/3D segregated perovskite structure, which improves the photoluminescence quantum yield remarkably at an excitation intensity up to 103mWcm-2. Accordingly, the top-emission PeLED that delivers a high maximum EQE above 20% is fabricated and can retain EQE>10% at an extremely high J of 708mAcm-2. These results represent one of the most efficient top-emission PeLEDs with ultra-low efficiency roll-off, which provide a viable methodology for tuning the dielectric response of perovskite films for improved high radiance performance of perovskite electroluminescence devices.

Effects of host-molecule transport polarities on the transient electroluminescence decay and efficiency roll-off of doped organic light-emitting diodes

Effects of host-molecule transport polarities on the transient electroluminescence decay and efficiency roll-off of doped organic light-emitting diodes

Constructing solution-processable heavy metal platinum (II) complex with narrowband emission by integrating multiple resonance molecular system

The narrowband emission required by wide color gamut display is an extremely important research topic for any luminescence mechanism, which has made significant progress in traditional fluorescence and thermally activated delayed fluorescence (TADF) based on purely organic compounds, but is far from mature in organometallic complexes. Herein, we propose a feasible molecular design paradigm for constructing the desirable organic electroluminescence (EL) emitter with narrowband emission by integrating an original multiple resonance TADF (MR-TADF) fragment into the classical platinum (II) complex. The solution-processed organic light-emitting diode (OLED) by employing the target model platinum (II) complex BNCPPt as the dopant emitter shows light green emission with a peak of 507 nm and narrow full-width at half-maximum (FWHM) of 35 nm, which achieves a maximum external quantum efficiency (EQE) of 13.5% with very low efficiency roll-off of 4.4% at 1000 cd m−2.

Mononuclear Cu(I) halide complexes containing asymmetric diphosphine and diphenyl pyridyl monophosphine: Structures and photophysical properties

Thermally activated delayed fluorescent (TADF) Cu(I) halide complexes have attracted attention due to their highly emission and short lifetimes (several μs scale). Here, three mononuclear four-coordinate Cu(I) halide complexes containing asymmetric diphosphine and pyridyl phosphine, [CuX(L1)(L2)] (L1 = 2,3-bis(diphenylphoshino)thiophene, L2 = 2-(diphenylphosphino)pyridine, X = I (1), Br(2), Cl (3)), were synthesized and their structures and photophysical properties were characterized. At room temperature, complexes 1–3 in powder exhibit intense green to yellow green delayed fluorescence (λem = 497–523 nm, τ = 1.5–4.3 μs, Φ = 0.19–0.28). The emissions of the complexes 1–3 are originated from (metal + halide)-to-ligand and intra-ligand charge transfer. More contributions from MLCT and XLCT can result in the shorter decay lifetimes (1.6 ∼ 4.3 μs), which will prevent a roll-off of efficiency with increasing current density in OLED devices.

High efficiency double light-emitting layer sky blue phosphor organic light-emitting diode with slow emission efficiency attenuation

In this study, by doping the iridium (III) double ((4,6-difluorobenzene) -pyridine-N, C2’Pyridinformate (FIrpic) into 4,4′, 4″ three (carbazole) trioxilamine (TcTa) and 9 (4 tert-butyl-benzene) −3,6 double (triphenylsilyl) -9H carbazole (CzSi) layers as light emitting layers (EMLs) to achieve sky blue phosphor organic electroluminescence (EL) devices with very low efficiency roll-off. The dependence of the EL performance on the doping concentration of the light-emitting molecules and the different EML thicknesses are studied in detail. Experimental data show that the thin-film-doped TcTa layer is very important for the efficiency of the device. Finally, the optimal device achieves extremely high power efficiency, current efficiency, and external quantum efficiency (EQE), reaching 74.82 lm/W, 66.68 cd/A, and 31.9 %, respectively. At a certain luminance of 2000 cd/m2 (3.4 V), the same device retained power efficiency with current efficiency and external quantum efficiency of 57.71 lm/W, 62.46 cd/A and 29.3 %, respectively, based on theoretical discussion, the improved EL efficiency was attributed to the energy levels of the host and luminescent molecules, which helps to balance the charge carrier in the emitter molecule distribution and expand the recombination region.

A Breakthrough in Solution-Processed Ultra-Deep-Blue HLCT OLEDs: A Record External Quantum Efficiency Exceeding 10% Based on Novel V-Shaped Emitters.

It is always a great challenge to achieve high-efficiency solution-processed ultra-deep-blue organic light-emitting diodes (OLEDs) with the Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates matching the blue primary of Rec. International Telecommunication Union-Radiocommunication BT.2100, which specifies high dynamic range television image parameters. Inspired by hybrid local and charge transfer (HLCT) excited state emitters improving exciton utilization through high-lying reverse intersystem crossing, here, a series of high-performance blue emitters by a V-shaped symmetric donor (D)-π-acceptor (A)-π-D design strategy are developed. Here, the large torsions and unstable bonds of D-A structures can be improved through π bridges, and also the conjugation length and donor groups can be easily adjusted. The obtained emitters merit excellent photophysical and electrochemical properties, thermal stability, solution processibility, and HLCT excited state excellence. Results suggest that the OLEDs based on the obtained blue emitters all achieve high maximum external quantum efficiency (EQEmax ) of more than 8% with very low efficiency roll-off. In particular, the device based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[fluorene-9,2'-imidazole] exhibits a satisfactory ultra-deep-blue emission (CIEx , y = 0.1579, 0.0387) and a record-high EQEmax (10.40%) among solution-processed HLCT OLEDs, which is very close to the record EQEmax of devices by vacuum vapor deposition technology.

Alignment of Heptagonal Diimide and Triazine Enables Narrowband Pure-Blue Organic Light-Emitting Diodes with Low Efficiency Roll-Off.

The endeavor to develop high-performance narrowband blue organic light-emitting diodes (OLEDs) with low efficiency roll-off represents an attractive challenge. Herein, we introduce a hetero-acceptor design strategy centered around the heptagonal diimide (BPI) building block to create an efficient thermally activated delayed fluorescence (TADF) sensitizer. The alignment of a twisted BPI unit and a planar diphenyltriazine (TRZ) fragment imparts remarkable exciton dynamic properties to 26tCz-TRZBPI, including a fast radiative decay rate (kR ) of 1.0×107 s-1 and a swift reverse intersystem crossing rate (kRISC ) of 1.8×106 s-1 , complemented by a slow non-radiative decay rate (kNR ) of 6.0×103 s-1 . Consequently, 26tCz-TRZBPI facilitates the fabrication of high-performance narrowband pure-blue TADF-sensitized fluorescence OLEDs (TSF-OLEDs) with a maximum external quantum efficiency (EQEmax ) of 24.3 % and low efficiency roll-off even at a high brightness level of 10000 cd m-2 (EQE10000 : 16.8 %). This showcases a record-breaking external quantum efficiency at a high luminance level of 10000 cd m-2 for narrowband blue TSF-OLEDs.

Design, synthesis, and properties of a novel red asymmetric luminescent material incorporating diphenylfumaronitrile, carbazole and acridine units

Herein, a deep red luminescent material BCZ-DBFN-AD containing asymmetric structure with both aggregation-induced emission (AIE) and hot exciton properties has been designed and synthesized through bilateral substitution molecular design strategy by introducing 9,9-dimethyl-9,10-dihydroacridine and carbazole electron donors with rotor effect on both sides of diphenylfumanitrile. The distorted molecular configuration and the introduction of larger rigid electron donors endow BCZ-DBFN-AD obvious AIE properties and high solid-state photoluminescence quantum yield (PLQY). Additionally, the distorted molecular configuration can also reduce the carrier injection barrier, activate the conversion channel from triplet exciton to singlet exciton, effectively take into account the locally excited (LE) state component and charge transfer (CT) state component in the hybrid excited state, and effectively improve the efficiency of the device. The PLQY of BCZ-DBFN-AD in the amorphous thin film is 31 %, and the maximum emission wavelength of the non-doped OLED prepared based on BCZ-DBFN-AD is 672 nm with Commission Internationale de L'Eclairage (CIE) coordinates of (0.64, 0.34). The Lmax, CEmax, PEmax, EQEmax are 2489 cd m−2, 1.01 cd A−1, 0.82 lm W−1, 1.83 %, respectively, the efficiency roll-off is only 3 %, and the exciton utilization rate is 29 %, which exceeds the upper limit of 25 % of traditional fluorescent materials.

Efficient and Bright Organic Radical Light-Emitting Diodes with Low Efficiency Roll-Off.

Organic radicals have been of interest due to their potential to replace nonradical-based organic emitters, especially for deep red/near-infrared (NIR) electroluminescence (EL), based on the spin-allowed doublet fluorescence. However, the performance of the radical-based EL devices is limited by low carrier mobility that causes a large efficiency roll-off at high current densities. Here, we report highly efficient and bright doublet EL devices by combining a thermally activated delayed fluorescence (TADF) host that supports both electron and hole transport and a tris(2,4,6-trichlorophenyl)methyl-based radical emitter. Steady-state and transient photophysical studies reveal the optical signatures of doublet luminescence mechanisms arising from both host and guest photoexcitation. The host system presented here allows balanced hole and electron currents, and we report a high maximum external quantum efficiency (EQE) of 17.4% at 707nm peak emission with substantially improved efficiency roll-off: over 70% of the maximum EQE (12.2%) is recorded at 10mA cm-2 , and even at 100mA cm-2 , nearly 50% of the maximum EQE (8.4%) is maintained. Charge recombination is primarily at the radical guest sites, but there is evidence from magneto-EL for host recombination and later energy transfer to the radical guest. We consider this is an important step to the practical application of organic radicals to NIR light-emitting devices. This article is protected by copyright. All rights reserved.

Efficient and stable green organic light-emitting diode utilizing an asymmetric butterfly-shaped chromophore with enhanced reverse intersystem crossing and suppressed exciton annihilation

Intermolecular electron-exchange interactions involving long-lived triplet state excitons dominate the quenching process of the films. In this work, a butterfly-shaped thermally activated delayed fluorescence (TADF) emitter 10,10′-(5-((3,5-di(9H-carbazol-9-yl)phenyl)sulfonyl)-1,3-phenylene)bis(9,9-dimethyl-9,10-dihydroacridine) (BCZ-DPS-BAD) with diphenylsulfone skeleton is constructed by modulating the rigid steric hindrance on the electron donor fragment to weaken intermolecular electron-exchange interactions. Analysis of the ground and excited state properties, crystal structure, steady-state and transient photophysical characteristics reveals that BCZ-DPS-BAD exhibits loose intermolecular arrangements with no direct facing close packing and weak π–π interactions of 4.18 Å and 4.67 Å. The triplet state excitons can swiftly return to the single exciton state in accordance with a short delayed fluorescence lifetime (2.3 μs) and a quick reverse intersystem crossing rate (1.85 × 106 s−1), obstructing the way for the triplet state to lose energy. A remarkable maximum external quantum efficiency of 21.8 %, maximum current efficiency of 56.8 cd/A and exciton utilization rate of 82 % is achieved for BCZ-DPS-BAD-based green non-doped OLED, concomitant with Commission Internationale d'Eclairage (CIE) coordinates of (0.30, 0.50). Notably, BCZ-DPS-BAD behaves stable non-doped OLED performance with efficiency roll-off of 4 % at 1000 cd m−2.

Triphenylene-Based Emitters with Hybridized Local and Charge-Transfer Characteristics for Efficient Nondoped Blue OLEDs with a Narrowband Emission and a Small Efficiency Roll-Off.

Developing high-efficiency nondoped blue organic light-emitting diodes (OLEDs) with high color purity and low-efficiency roll-off is vital for display and lighting applications. Herein, we developed two asymmetric D-π-A blue emitters, PIAnTP and PyIAnTP, in which triphenylene is first utilized as a functional acceptor. The relatively weak charge transfer (CT) properties, rigid molecular structures, and multiple supramolecular interactions in PIAnTP and PyIAnTP can significantly enhance the fluorescence efficiency and suppress the structural relaxations to obtain a narrowband blue emission. The photophysical experiments and theoretical simulations reveal that they both exhibit a typical hybridized local and charge-transfer (HLCT) excited state and achieve high external quantum efficiency (EQE) via a "hot exciton" channel. As a result, PIAnTP- and PyIAnTP-based nondoped devices realize blue emission at 456 and 464 nm, corresponding to CIE coordinates of (0.16, 0.14) and (0.16, 0.19), narrow full width at half-maximums of 52 and 60 nm, and the high EQEs of 8.36 and 8.69%, respectively. More importantly, the PIAnTP- and PyIAnTP-based nondoped devices show small EQE roll-offs of only 5.9 and 2.4% at 1000 cd m-2, respectively. These results signify an advance in designing a highly efficient blue emitter for nondoped OLEDs.

Efficient non-doped sky-blue fluorescent organic light emitting devices based on cyanopyridine-containing anthracene derivatives

Two new cyanopyridine-containing anthracene derivatives with asymmetrical donor-π-acceptor (D-π-A) molecule structure have been successfully synthesized by Suzuki coupling reaction, namely 4-(10-(9-phenyl-9H-carbazol-3-yl)anthracen -9-yl)benzonitrile (3CzAnPyCN) and 4-(10-(4-(9H-carbazol-9-yl)phenyl)anthracen -9-yl)benzonitrile (pCzAnPyCN). The non-doped organic light emitting devices (OLEDs) using 3CzAnPyCN and pCzAnPyCN as emitters simultaneously achieved high efficiency stable sky-blue luminescence, corresponding to the maximum external quantum efficiency (EQE) of 8.07% and 8.13% with the Commission International de L'Eclairage (CIE) coordinates of (0.18, 0.35) and (0.16, 0.24), respectively. In addition, extremely low efficiency roll-offs were also evaluated in this work. The EQE values remained as high as 7.80% and 7.88% at the luminance of 1000 cd/m2, 7.31% and 6.95% at the luminance of 10000 cd/m2 for 3CzAnPyCN and pCzAnPyCN, respectively. It is found, by photophysical experiments and density functional theory analysis, that the excited state property of the luminogens revealed that the “hot excitons” induced reverse intersystem crossing (RISC) played a crucial role in improving efficiency. Such an excellent electroluminescence (EL) performance achieved in these non-doped OLEDs is among the highest values based on sky-blue fluorescent materials, potential for future optical applications.

Positional Isomeric Cyano-Substituted Bis(2-phenylpyridine)(acetylacetonate)iridium Complexes for Efficient Organic Light-Emitting Diodes with Extended Color Range.

Bis(2-phenylpyridine)(acetylacetonate)iridium, Ir(ppy)2(acac), is a benchmark green emitter for phosphorescent organic light-emitting diodes (PhOLEDs). In this work, we reported three positional isomeric cyano-substituted Ir(ppy)2(acac) complexes, i.e., Ir(3-CN), Ir(4-CN), and Ir(10-CN), with the emission in the yellow to red region (544-625 nm). Through theoretical investigation and single-crystal analysis, it was found that the introduction of cyano substitution at various positions of the ppy ligand allows for tuning the electron distribution and coordination bond length of Ir complexes. Therefore, the charge transfer property of Ir complexes is enhanced such that the energy gap of the cyano-substituted Ir(ppy)2(acac) complexes was reduced. In addition, Ir(3-CN), Ir(4-CN), and Ir(10-CN) exhibited high PLQYs of 83, 54, and 75%, respectively, with the phosphorescence lifetime in the range of 0.79-2.08 μs. Notably, the device utilizing Ir(3-CN) as the emitter exhibited a maximum external quantum efficiency (EQE) of 25.4%, current efficiency of 56.9 cd A-1, power efficiency of 68.7 lm W-1, and brightness of 61,340 cd m-2 at 8 V. The EQE of this device remained 24.3 and 19.9% at luminances of 1,000 and 10,000 cd m-2, corresponding to the efficiency roll-off of 4.3 and 21.7%, respectively. Comparing to the Ir complexes using the ligand with an extended conjugated structure, our results demonstrated a simple molecular design strategy for phosphorescence emitters with reduced molecular weight for efficient PhOLEDs in the yellow to red color region.

Synthesis and characterization of a novel thermally stable silane-based host material for blue phosphorescent organic light-emitting diodes

We report a novel thermally stable host material, namely, bis[3-(2-indolo[3,2,1-jk]carbazolyl)phenyl)diphenylsilane (Si-IDCz), for use in blue phosphorescent organic light-emitting diodes (PhOLEDs). Here, Si-IDCz exhibits a high glass transition temperature (Tg) of 151 °C as it contains a thermally stable silane moiety. Additionally, the rigid silicon core within Si-IDCz effectively suppresses molecular interactions, resulting in a wide bandgap and high triplet energy. Here, we used Si-IDCz as the single host for the blue PhOLEDs. The blue PhOLED with the single-host Si-IDCz exhibited an external quantum efficiency (EQE) of over 15%; an EQE of over 11% was maintained at a high luminance of 5000 cd/m2 owing to the high thermal stability of the Si-IDCz. Furthermore, an improved EQE of more than 20% was achieved by introducing a mixed-host system to enhance the photoluminescence quantum yield; the efficiency roll-off was reduced as well.

Low-trigger voltage and efficient phosphorescent organic light-emitting diodes with bipolar TADF host

Thermally activated delayed fluorescence (TADF) materials have continued to attract interest due to their rapid improvements in efficiency, non-toxic and potential to be manufactured at energy-saving organic light-emitting diode for full-color display and solid-state lighting. Here, The bipolar and electroluminescence (EL) characteristics of TADF host, 11-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-12,12-dimethyl-11,12-dihydroindeno[2,1-a]carbazole (DPDDC), were investigated. By incorporating the phosphorescent tris[2-(p-tolyl)pyridine]iridium(III) [Ir(mppy)3] dopant into the matrix, DPDDC showed more excellent EL performance compared with the typical 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) host. The turn-on voltage for phosphorescent organic light-emitting diodes (PhOLEDs) was decreased to 2.2 V from 2.5 V by exploiting the TADF host instead of CBP. Crucially, we found that the ratio of Ir(mppy)3 in TADF host plays a significant role in EL process. Remarkable low efficiency roll-off was achieved with above 90% of the current efficiency maintained even at a brightness of 3000 cd m−2, along with high power efficiency of 84.8 lm·W−1 and the external quantum efficiency of 20.6% for DPDDC: 5 wt% Ir(mppy)3-based device.

Manipulating the excited states from charge-transfer to hybridized local and charge-transfer towards high-performance blue electroluminescence

Manipulating the excited states of organic luminescent materials can efficiently improve the utilization of both singlet and triplet excitons for developing high-performance organic light-emitting diodes (OLEDs), but the issue remains difficult due to the lack of well-controlled ways. Here, we proposed a molecular design strategy of excited state manipulation from charge-transfer (CT) to hybridized local and charge-transfer (HLCT) via adjusting the cyano position on pyridine acceptor. The meta-substituted PyAn4CN is mainly composed of a CT component, while the para-substituted PyAn5CN is endowed with a HLCT component. On further extending the conjugation of PyAn5CN by inserting a benzene unit between the pyrene and anthracene core, the HLCT character is preserved in PyPhAn5CN, accompanied by a faster radiative decay. Consequently, the vacuum-evaporated OLEDs exhibit blue electroluminescence (EL) with the emission peaks in the range of 455–460 nm and high external quantum efficiency (EQE) up to 7.52%, together with well-suppressed efficiency roll-offs of 0.8% and 3.7% at the luminance of 100 and 1000 cd m-2, respectively. More importantly, the solution-processed device shows an excellent performance with EQE of 6.49%, which is one of the best results in the solution-processed HLCT OLEDs. Our results clearly indicate that the formation of HLCT state is an efficient way to realize high-efficiency blue electrofluorescence.

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.

A modeling approach to understanding OLED performance improvements arising from spatial variations in guest:host blend ratio.

Phosphorescent organic light emitting diodes (OLEDs) suffer from efficiency roll off, where device efficiency rapidly decays at higher luminance. One strategy to minimize this loss of efficiency at higher luminance is the use of non-uniform or graded guest:host blend ratios within the emissive layer. This work applies a multi-scale modeling framework to elucidate the mechanisms by which a non-uniform blend ratio can change the performance of an OLED. Mobility and exciton data are extracted from a kinetic Monte-Carlo model, which is then coupled to a drift diffusion model for fast sampling of the parameter space. The model is applied to OLEDs with uniform, linear, and stepwise graduations in the blend ratio in the emissive layer. The distribution of the guests in the film was found to affect the mobility of the charge carriers, and it was determined that having a graduated guest profile broadened the recombination zone, leading to a reduction in second order annihilation rates. That is, there was a reduction in triplet-triplet and triplet-polaron annihilation. Reducing triplet-triplet and triplet-polaron annihilation would lead to an improvement in device efficiency.

Peripheral decoration of multi-resonance TADF emitter for narrowband blue OLEDs

Multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters with high efficiency and narrowband blue emission are highly demanded for high-quality displays. In this study, two MR-TADF emitters, namely CzBN-tDPA and CzBN-mCP, were designed by decorating the well-known emitter of CzBN with different diarylamino moieties. This peripheral decoration strategy successfully results in blue emission with peaks at 465 and 464 nm, narrow full-width at half maximum (FWHM) values of 23 and 21 nm for CzBN-tDPA and CzBN-mCP in toluene solution, respectively. The new emitters exhibit faster rate constants of reverse intersystem crossing and higher photoluminescence quantum yields, compared to the parent molecule. As a result, organic light-emitting diodes based on CzBN-tDPA and CzBN-mCP exhibit narrowband blue emission with maximum external quantum efficiencies (EQEmaxs) of nearly 20% and low efficiency roll-offs. More importantly, decent EQEmax up to 30.6% could be realized in hyperfluorescence devices adopting these two new emitters.

Exciton Dynamics and Optically Pumped Lasing in 1‐Naphthylmethylamine‐Based Quasi‐2D Perovskite Films

AbstractFilms of the quasi‐2D perovskite based on 1‐naphthylmethylamine (NMA) are promising as the gain medium for optically pumped lasing and future electrically pumped lasing because of its low lasing threshold and small electroluminescence efficiency rolloff. However, reasons for the low threshold and small efficiency rolloff are still unclear. Therefore, exciton dynamics are investigated in NMA‐based quasi‐2D perovskite films. It is found that quenching of bright excitons by other excitons or charge carriers is unlikely in NMA‐based quasi‐2D perovskite films, which is one reason for the low lasing threshold and small efficiency rolloff. Moreover, thermally stimulated current measurements reveal that the defect levels inside the band gap of the NMA‐based quasi‐2D perovskite are shallow, with a depth of ≈0.3 eV, causing a decrease in nonradiative exciton recombination through the defects. Therefore, population inversion can be easily achieved, leading to the low lasing threshold as well. For fabrication of NMA‐based quasi‐2D perovskite laser devices with even lower lasing thresholds, a circular‐shaped optical resonator, and small‐molecule‐based defect passivation are used. Optically pumped lasing can be obtained from these devices, with a threshold of ≈1 µJ cm−2, which is one of the lowest values ever reported in any perovskite lasers.