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Since the first development of organic light-emitting diodes (OLEDs) in 1987, imidazole derivatives, mainly including phenanthroimidazole (PI) and benzimidazole (BI), have increasingly attracted attention. Their strong electron-withdrawing properties make them suitable for emitters, hosts, and electron-transporting materials (ETMs). In this review, an overview of the recent developments regarding OLEDs based on imidazole derivatives, especially the relationship between the molecule structure and the device performance as fluorescent and host materials, is given.

Here, using a strategy called “V-shaped layout of triplet energy levels (ETs)”, a high-T1, electron-deficient and bulky 1,5-diazarcarbazole (15NCz) was first introduced for the construction of new electron-transporting materials (ETMs). When 9,10-diphenylanthracene (DPA) was encapsulated by 15NCz at different positions, a series of ETMs with high electron mobility and good thermal stability were designed and synthesized: 9-(4-(9-([1,1′-biphenyl]-4-yl)anthracen-10-yl)phenyl)-9H-1,5-diazarcarbazole (p-S15NCzDPA), 9-(3-(9-([1,1′-biphenyl]-3-yl)anthracen-10-yl)phenyl)-9H-1,5-diazarcarbazole (m-S15NCzDPA), 9,10-bis(4-(9H-1,5-diazarcarbazole-9-yl)phenyl)anthracene (p-D15NCzDPA) and 9,10-bis(3-(9H-1,5-diazarcarbazole-9-yl)phenyl)anthracene (m-D15NCzDPA). When these novel ETMs were used in triplet–triplet fusion (TTF) fluorescent OLEDs, they exhibited superior performance compared to devices using the common ETMs TPBi and TmPyPB. In particular, devices based on m-S15NCzDPA and m-D15NCzDPA offered a maximum luminance (Lmax) of 66 100 and 66 950 cd m−2, maximum current efficiency (CEmax) of 17.40 and 17.20 cd A−1, and maximum power efficiency (PEmax) of 12.20 and 11.70 lm W−1 with a maximum external quantum efficiency (EQEmax) of 9.00% and 8.66%, respectively. More importantly, the device based on m-D15NCzDPA also achieved lower efficiency roll-offs at high luminance (roll-offs of 2.3% and 13.9% at 10 000 and 50 000 cd m−2, respectively). This work demonstrated that a V-shaped layout of ETs strategy was beneficial for the construction of a series of high-performance ETMs.

In this manuscript, by utilizing limited conjugation of carbazole and easily realizing triplet–triplet annihilation properties of 4-(anthracen-9-yl)benzonitrile, two new blue materials 4-(10-(9-phenyl-9H-carbazol-3-yl)anthracen-9-yl)benzonitrile (3CzAnBzt) and 4-(10-(4-(9H-carbazol-9-yl)phenyl)anthracen-9-yl)benzonitrile (pCzAnBzt) were designed and synthesized. In both cases, these compounds exhibited small energy gap and orbit overlapped between excited state of Tm and Sn, which would accelerate the triplet–triplet annihilation process. Additionally, when these two compounds were used as emitters in nondoped devices, the triplet energy was utilized efficiently through triplet–triplet annihilation, excellent blue electroluminescence performances were achieved. The maximum external quantum efficiency values were 10.06% and 9.23% for 3CzAnBzt and pCzAnBzt, respectively. The efficiency roll-off for 3CzAnBzt and pCzAnBzt were very low, the EQEs still remained 8.97% and 7.10% at the luminescence of 1000 cd m−2. (0.14, 0.14) and (0.14, 0.10) are the Commission International de L’Eclairage coordinates for 3CzAnBzt and pCzAnBzt, respectively, at the voltage of 6 V. Up to now, the outstanding EL performances were the state-of-the-art compared to previously reported nondoped blue EL devices.

Dimethyl acridine (Ac) and carbazole (Cz) donors are fused to produce acridine–carbazole hybrid donors 12AcCz (8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine) and 23AcCz (13,13-dimethyl-7-phenyl-7,13-dihydro-5H-indolo[3,2-b]acridine). By combining the TPPM (2,4,6-triphenylpyrimidine) acceptor with the Ac–Cz-fused donors of 12AcCz and 23AcCz, two emitters, 12AcCz-PM (13-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-8,8-dimethyl-5-phenyl-8,13-dihydro-5H-indolo[2,3-c]acridine) and 23AcCz-PM (5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-13,13-dimethyl-7-phenyl-7,13-dihydro-5H-indolo[3,2-b]acridine), are designed and synthesized. The impact of the different fused topologies of the hybrid donors on the molecular configuration and photophysical and optoelectrical properties is systematically investigated. For 12AcCz-PM, the large steric hindrance between the donor and acceptor compels Ac of 12AcCz to be crooked, which endows it with a relatively planar quasi-axial conformation. No blatant TADF character is observed, but the 12AcCz-PM doped device still presents ultradeep blue emission with CIEx,y of (0.15, 0.05) and a maximum external quantum efficiency (EQEmax) of 6.4%. Whereas, 23AcCz-PM shows a quasi-equatorial conformation and possesses notable TADF behavior. The 23AcCz-PM doped device reachs an EQEmax of 28.4% at low dopant concentration and 26.1% at high dopant concentration. Additionally, low efficiency roll-off (EQEs of 24.8% at 1000 cd m−2 and 20.7% at 5000 cd m−2) further confirms its superiority as a TADF emitter.

A series of 1,2,4-thiadiazole core-based bipolar materials, 2,2′-(1,2,4-thiadiazole-3,5-diyl)bis(N,N-diphenylaniline) (o-TPATHZ), 3,3′-(1,2,4-thiadiazole-3,5-diyl)bis(N,N-diphenylaniline) (m-TPATHZ) and 4,4′-(1,2,4-thiadiazole-3,5-diyl)bis(N,N-diphenylaniline) (p-TPATHZ) were developed as the host matrixes for the deep red phosphorescent emitters tris(1-phenylisoqiunoline) iridium (Ir(piq)3) and [bis(2-methyldibenzo-[f,h]-quinoxaline) Ir(III)(acetylacetonate)] (Ir(MDQ)2(acac)). By systematic studying, we demonstrated that there are two types of charge-trapping effect within the emissive layers through adjusting the host-guest compatibility. And, it is revealed that a symmetric charge-trapping effect can contribute to realizing a stable charge-balance, which led to a mitigating efficiency roll-off at high current density. Consequently, a maximum external quantum efficiency (EQE) of 16.2% was achieved by an optimized device with p-TPATHZ-Ir(piq)3 emissive layer. Remarkably, the EQE still remained as high as 15.7% at the high luminance of 1000 cd/m2.

In this study, 4,6-diphenyl-1,3,5-triazine as the rotor, was firstly introduced to the construction of AIEgens. By conjugating phenyl-9H-carbazole and 4,6-diphenyl-1,3,5-triazine to the 9 or 10 position of anthracene, three new multifunctional aggregation-induced emission (AIE) fluorophores, 3-(10-(4,6-diphenyl-1,3,5-triazin-2-yl)anthracen-9-yl)-9-phenyl-9H-carbazole (3CzAnTrz) 9-(4-(10-(4,6-diphenyl-1,3,5-triazin-2-yl)anthracen-9-yl)phenyl)-9H-carbazole (pCzAnTrz) and 9-(3-(10-(4,6-diphenyl-1,3,5-triazin-2-yl)anthracen-9-yl)phenyl)-9H-carbazole (mCzAnTrz) were designed and synthesized. The photophysical properties indicated that all three compounds not only exhibited an AIE effect but also showed a reversible piezofluorochromic (PFC) behaviour. The experimental results revealed that the spectral shifts ΔλPFC (ΔλPFC = λrepressed – λannealed) were obviously influenced by the linking position of 9-phenyl-9H-carbazole, and 3CzAnTrz showed largest spectral shifts (ΔλPFC = 66 nm), because of the relatively loose molecular packing, weak intermolecular CH-π interactions and more twisted conformation. When three fluorophores were used as emitter in the nondoped sky-blue devices, these devices showed excellent electroluminescence (EL) performances, realizing the maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) values of 13.34 cd A−1, 11.59 lm W−1, 5.44%; 11.19 cd A−1, 9.25 lm W−1, 5.54% and 8.74 cd A−1, 6.44 lm W−1, 4.71% for 3CzAnTrz, pCzAnTrz, and mCzAnTrz, respectively. And these devices exhibit negligible efficiency roll-off even at 10000 cd m−2. These results manifest that the potential advantage of multifunctional AIEgens applicable for piezofluorochromism and nondoped high-performance EL devices.

Formamidinium (FA) lead bromide (FAPbBr3) perovskite nanocrystals (P-NCs) have ultrapure green emission and high stability, while FAPbBr3 NCs based light-emitting diodes (FA-NLEDs) still have little report. Here, FAPbBr3 NCs with a high photoluminescence quantum yield of 85.8% were synthesized. By controlling the concentration of FAPbBr3 NCs in toluene solution, the exciton recombination region was precisely confined to the emitting layer and the parasitic emission coming from electron transport layer disappeared, resulting in the pure green emissions. The optimized FA-NLED presents a maximum external quantum efficiency (EQE), current efficiency (CE) of 3.84% and 16.08 cd/A respectively, with the EL emission peak of 528 nm, CIE of (0.183, 0.763) and a full width of half-maximum (FWHM) of 24 nm, which is among the best performance of FA-NLEDs.

The development of efficient and robust, deep-blue, thermally activated delayed fluorescence (TADF) emitters, especially those matching the European Broadcasting Union (EBU) standard with Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.06), is one of the challenging issues in organic light-emitting devices (OLEDs). Through sophisticated molecular engineering, two novel pyrimidine derivatives with D-π-A configuration, 5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (pBFCz-26DPPM) and 5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-5H-benzo [4,5]thieno[3,2-c]carbazole (pBTCz-26DPPM) have been designed and synthesized. There are only negligible differences in the molecular configuration and thermal, electrochemical and photophysical properties for the two compounds. However, TADF properties can be tuned by changing the heteroatom in the donor moiety. Compound pBFCz-26DPPM offers a shorter delayed fluorescence lifetime (τd) than that of pBTCz-26DPPM. The optimized device serving pBFCz-26DPPM as dopant presents deep-blue Commission Internationale de l’Eclairage (CIE) coordinates of (0.154, 0.054) and maximum external quantum efficiencies (EQEmax) of 6.20%. Remarkably, no-doped device based on pBFCz--26DPPM delivers CIE coordinates of (0.153, 0.067) and EQEs as high as 5.80%. These device performances are amongst some of those of the best performing deep blue TADF OLEDs with similar color gamut.

Here, a phenanthroimidazole moiety was firstly introduced into the construction of thermally activated delayed fluorescence (TADF) emitters, and two novel TADF emitters consisting of phenanthroimidazole as the acceptor group and phenazine as the donor group, 1-(4-(tert-butyl)phenyl)-2-(4-(10-phenylphenazin-5(10H)-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (PPZTPI) and 1-phenyl-2-(4-(10-phenylphenazin-5(10H)-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (PPZPPI) were designed and synthesized. The highly twisted conformation between phenazine and phenanthroimidazole in the molecules results in effective spatial separation of the HOMO and LUMO and small singlet–triplet splittings. Both compounds possess obvious TADF features. Their crystallographic properties, electronic structures, thermal stabilities, photophysical properties, and energy levels are studied systematically. Organic light-emitting diodes (OLEDs) using these two green TADF emitters demonstrate high external quantum efficiencies of 21.06% for PPZPPI and 20.52% for PPZTPI, respectively, which is comparable to most of the previously reported TADF OLEDs.

Molecular structures play a critical role in forming the horizontal orientation of the emission transition dipole of light-emitting TADF materials which can improve the light outcoupling efficiency of OLEDs. Here, two TADF emitters of IndCzpTr-1 and IndCzpTr-2 based indolocarbazole derivatives with stereoscopic and linear structures were designed and synthesized. With a smaller ΔEST, better thermal stability and preferential horizontal orientation with an orientation order parameter S of −0.264, a green TADF OLED device based on IndCzpTr-2 realized a maximum EQE of 30.0% and maximum current efficiency (CE) of 82.6 cd A−1 without using any optical outcoupling technology; meanwhile, a sky-blue TADF OLED with a maximum EQE of 14.5% and a maximum CE of 28.1 cd A−1 was obtained for IndCzpTr-1 with a homologous device structure.

Three novel TADF materials, 10-(6-(2,6-diphenylpyrimidin-4-yl)pyridin-3-yl)-9,9-diphenyl-9,10-dihydroacridine (DPAc-4PyPM), 9,9-diphenyl-10-(4-(2-phenyl-6-(pyridin-2-yl)pyrimidin-4-yl)phenyl)-9,10-dihydroacridine (DPAc-6PyPM) and 10-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-9,9-diphenyl-9,10-dihydroacridine (DPAc-TPPM) have been designed and synthesized. CH⋯N intramolecular hydrogen-bonding interactions were introduced into pyrimidine–pyridine hybrid acceptors, then the TADF properties can be tuned by skillful manipulation of the positions of CH⋯N in the acceptor moiety. Both DPAc-4PyPM and DPAc-6PyPM exhibit a higher PLQY than DPAc-TPPM. Simultaneously, the kRISC realized for DPAc-4PyPM is nearly 5 or 10 fold higher than that of its analogues. The optimized sky-blue device using DPAc-4PyPM as a dopant demonstrated the maximum external quantum efficiency, current efficiency and power efficiency of 24.34%, 53.89 cd A−1 and 36.79 lm W−1, respectively, which is comparable to most of the previously reported pyrimidine-based TADF OLEDs.

A novel electron acceptor based on 10-phenyl-10H-phenothiazine 5,5-dioxide (2PTO) was introduced for the first time to construct aggregation-induced delayed fluorescence materials. The emitter PXZ2PTO contains phenoxazine as the electron donor, exhibiting both AIE characteristics and TADF properties. Due to the highly stereoscopic structure and small ΔEST of PXZ2PTO, a green non-doped TADF OLED realized a high maximum EQE, CE and PE of 16.4%, 44.9 cd A−1 and 32.0 lm W−1, respectively, without using any optical outcoupling technology, which is comparable with the best reported non-doped TADF OLEDs. In addition, the efficiency of the non-doped devices are comparable with that of doped PXZ2PTO devices, with the maximum EQE, CE and PE of 16.3%, 43.8 cd A−1 and 35.2 lm W−1, respectively.

Efficient white organic light-emitting diodes (WOLEDs) with high stability are highly desired nowadays to produce devices that meet the commercial illumination requirement. WOLEDs based on single-host emission layer, is a preferred route to simplify device structures and thus lower the production cost. In this work, we report on single-host WOLEDs based on bipolar material, 2,6-bis[(3-carbazol-9-yl)phenyl)]pyridine (26DCzPPy), as the host, and Iridium (III)bis[(4,6-difluorophenyl)-pyridinato-N,C 2′ ] (FIrpic), [3,2-c]pyridinato-N,C 2′ ) acetylacetonate (PO-01), as blue and yellow dopants, respectively. The devices exhibit not only higher efficiency, but also superior stability compared to the conventional devices and doping-free devices. Detailed analysis is conducted to clarify the underlying reasons. This work enriches the mechanism understanding of single-host devices and paves the way for development of high performance WOLEDs.

A span-new electron-deficient moiety 2,5-diazarcarbazole (25NCz) with high T1 = 2.77 eV was firstly designed and synthesized, which had enormous potential to construct organic electronic materials in photoelectric field. Herein, 25NCz as large rigid-type periphery functionalized group, was introduced to develop novel electron transporting materials (ETMs) by grafting large rigid-type π-conjugated core anthracene. Two novel ETMs p-S25NCzDPA and p-D25NCzDPA were designed and developed. Due to the dual characteristics of rigidity and electron-accepting of the 25NCz, as expected, these two ETMs possessed good thermal stability and high electron mobility. When triplet-triplet fusion (TTF) sky-blue fluorescent OLEDs based on these two novel ETMs were manufactured, they exhibited superior performances. In particular, the maximum external quantum efficiency (EQE) reached 7.45% and the EQE kept 7.45% at the luminance of 50,000 cd m−2 for p-S25NCzDPA based device. This work rationally demonstrated that the significance of newly developed electron-deficient moiety 25NCz in designing ETMs for high-performance OLEDs.

Efficient phosphorescent white organic light-emitting devices (WOLEDs) based on a novel phosphine oxide host, 4,6-bis(diphenylphosphoryl)dibenzofuran (DBFDPO), with particularly low turn-on voltage and high color stability are reported. Without any electrical doping (p-doing or n-doping) strategies, the simplified optimal WOLEDs utilizing DBFDPO as the same host for blue/yellow emitters show low operating voltages, 1 cd/m 2 at 2.5 V (turn-on voltage), 46 cd/m 2 at 3 V and 2787 cd/m 2 at 5 V, and 12840 cd/m 2 at 7 V, respectively. A forward-viewing current efficiency (CE) of 41.3 cd/A (power efficiency (PE) of 34.0 lm/W) is achieved at the luminance of 673.4 cd/m 2 without any out-coupling enhancement structures. Furthermore, improved color stability is achieved through adjusting the yellow emitting layer. The Commission Internationale de I’Eclairage coordinates (CIE) of the optimal WOLED merely shift from (0.330, 0.405) to (0.327, 0.400) over a wide range of luminance (10–10,000 cd/m 2 ). We have revealed that the competition of the two mechanisms of energy transfer and carrier-trapping/-assist transport severely impact on the spectra stability.

CsPbBr3 nanocrystals (NCs) with enhanced photoluminescence quantum yield (PLQY) and stability have been regarded as promising emissive materials in flexible, low-cost, and high-definition display applications. The long-chain organic ligands, i.e. oleylamine and oleic acid, are essential to stabilize the NCs and increase their PLQY, but the long-chain ligands show detrimental effects on the charge transport ability of the resultant NCs, which deteriorate the performance of light emitting diodes (LEDs). Here, we introduced Na+ ions during the synthesis of perovskite NCs. Because of strong ionic bonding between Na+ and Br− ions, the introduced Na+ ions could stabilize the Br− ions hanged on the surface, which is beneficial to suppressing the generation of Br− vacancies. In addition, when the Na+ ions were capped on perovskite surface, the amount of long-chain organic ligands on the surface of perovskite NCs were reduced. As a result, high-quality perovskite NCs with uniform microstructure, high PLQY of 84.6%, and improved charge transport ability are achieved with appropriate addition of Na+ ions, which enables us increase the EQE of a LED device from 5.59% to 7.33%.

Herein, large π-conjugated core anthracene with an innate bipolar property was employed to construct multifunctional organic electronic materials. Delicate manipulating molecules via combining anthracene core and large periphery groups, two asymmetric anthracene derivatives namely (4-(10-(4-(9H-1,5-diazacarbazole-9-yl)phenyl)anthracen-9-yl)phenyl)diphenylphosphine oxide (p-PO15NCzDPA) and (3-(10-(3-(9H-1,5-diazarcarbazole-9-yl)phenyl)anthracen-9-yl)phenyl)diphenylphosphine oxide (m-PO15NCzDPA) were firstly designed and developed. The large periphery groups 1,5-diazarcarbazole (15NCz) and diphenylphosphine oxide (PO) efficiently interrupt the intramolecular π-conjugation, presenting an asymmetric bulky periphery enveloping strategy achieving highly twisted structures, which help to realize deep-blue emission. Meanwhile, due to the high PLQY and well-balanced bipolar transport characteristics, desired device addressing the contradiction of efficiency, color gamut and structure complexity is within reach. Detailed device engineering study was carried out, in which p-PO15NCzDPA and m-PO15NCzDPA were functioned as multifunction layers. As expected, p-PO15NCzDPA-based homogenous and unilateral homogenous OLEDs exhibited outstanding performance with impressive EQEmax of 4.55% and 6.40%, deep blue CIE coordinates of (0.152, 0.075) and (0.151, 0.066) at the voltage of 6 V, narrow FWHM of 46 nm and 50 nm, respectively. More importantly, the simplified homogenous device achieved extremely low efficiency roll-offs of 1.3% and 4.8% at 1000 and 5000 cd m−2, respectively. These results are among the most outstanding performance, which provided a guide for further improving the performance of deep blue fluorescent OLEDs and simplifying the structure of OLEDs.

Efficient deep-blue thermally activated delayed fluorescence (TADF) emitters are still very scarce. It is available to render the color bluer by reducing the intensity of intramolecular charge transfer (ICT) between acceptor and donor. Here, attaching the acceptor of six-membered heterocyclic diphenylsulfone-derivative (2PTO) with donors (DMAc and DPAc), two compounds, 2-(9,9-dimethyl-acridin-10(9H)-yl)-10-phenyl-10H-phenothiazine 5,5-dioxide (DMAC2PTO) and 2-(9,9-diphenylacridin-10(9H)-yl)-10-phenyl-10H-phenothiazine 5,5-dioxide (DPAC2PTO) were designed and synthesized. Due to the largely twisted configuration and weak ICT, DMAC2PTO with small singlet-triplet energy gap (ΔEST) displayed TADF feature and deep-blue emission. Moreover, DPAC2PTO exhibited much lower photoluminescence quantum yield (PLQY) than DMAC2PTO. The doped device of DMAC2PTO achieved a maximum external quantum efficiency (EQEmax) of 15.2% with a deep-blue color coordinate (CIEx,y) of (0.154, 0.108), and showed a narrow emission spectra with a 52 nm full width at half maximum (FWHM). In addition, the non-doped device of DMAC2PTO reached the EQEmax of 8.36% with CIEx,y of (0.158, 0.157).

Formamidinium lead bromide (FAPbBr(3)) nanocrystals (NCs) demonstrate great potential in light-emitting diode (LED) applications due to their pure green emission and excellent stability. However, t ...

In this paper, the periphery of aggregation-induced emission-thermally activated delayed fluorescence (AIE-TADF) chromophore (DPS-PXZ) was modified with host-substituents (DCB, mCP, pPhDCz and mPhDCz). Four self-host TADF emitters, namely DCB-DPS-PXZ, mCP-DPS-PXZ, pPhDCzDPSPXZ and mPhDCzDPSPXZ, were designed and synthesized. Here, the effect of host-substituents with different linking topologies on TADF has been investigated. Among them, the pPhDCz and mPhDCz substituted AIE-TADF emitters have stronger AIE effect than that of DCB and mCP based ones, which due to the larger twist angle between host substituents and DPS-PXZ. And then, mPhDCzDPSPXZ and pPhDCzDPSPXZ could obtain the PLQYs of 56% and 55% in the neat film, respectively. The PLQY values were higher than that of DCB-DPS-PXZ (40%) and mCP-DPS-PXZ (47%). Based on these advantages, the maximum EQE and the efficiency roll-off at 1000 cd/m2 of the non-doped OLEDs were 18.1% and 7.7% for mPhDCzDPSPXZ, 17.1% and 9.9% for pPhDCzDPSPXZ, respectively. However, the maximum EQEs of DCB-DPS-PXZ and mCP-DPS-PXZ based non-doped devices were only 13.9% and 14.7%, respectively. Therefore, the careful modification of the AIE-TADF chromophore by changing host-substituent types and linking positions appropriately was beneficial for the realization of efficient and low efficiency roll-off non-doped OLEDs.

The nondoped thermally activated delayed fluorescence (TADF) devices are increasingly attracting attention due to the superior performances and simple fabrication process. By incorporating two acceptors with phenothiazine, two materials 2-(10H-phenothiazine-10-yl)-10-phenyl-10H-phenothiazine-5,5-dioxide (PTZ-2PTO) and 3-(10H-phenothiazin-10-yl)-10-phenylacridin-9(10H)-one (PTZ-AD) are designed and investigated. Both the two materials possess dual conformations, whereas the quasi-axial conformer is the main configuration of PTZ-2PTO and quasi-equatorial conformer of PTZ-AD is more stable. The quasi-axial conformers show classical fluorescence emission, and the quasi-equatorial conformers exhibit TADF characteristic. Fascinatingly more, efficient energy transfer can be achieved between quasi-axial conformers and quasi-equatorial conformers, exhibiting similar mechanism to the traditional host-guest system. Based on this characteristic, yellow nondoped TADF-OLED device of PTZ-AD has realized the efficiency of up to 17.08%, 50.48 cd A−1 and 60.04 lm W−1. Meanwhile, the PTZ-AD based nondoped device exhibits low turn-on voltage and low efficiency roll-off, which is among the best performance for yellow nondoped TADF devices. In addition, PTZ-AD based doped device realizes high efficiency of 20.23%, 61.04 cd A−1 and 68.45 lm W−1. This dual conformations forming host-guest system provides a new strategy for obtaining highly efficient nondoped OLEDs devices.