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Although the organic light‐emitting diode (OLED) has been successfully commercialized, the development of deep‐blue OLEDs with high efficiency and long lifetime remains a challenge. Here, a novel hyperfluorescent OLED that incorporates the Pt(II) complex (PtON7‐dtb) as a phosphorescent sensitizer and a hydrocarbon‐based and multiple resonance‐based fluorophore as an emitter (TBPDP and ν‐DABNA) in the device emissive layer (EML), is proposed. Such an EML system can promote efficient energy transfer from the triplet excited states of the sensitizer to the singlet excited states of the fluorophore, thus significantly improving the efficiency and lifetime of the device. As a result, a deep‐blue hyperfluorescent OLED using a multiple resonance‐based fluorophore (ν‐DABNA) with Commission Internationale de L'Eclairage chromaticity coordinate y below 0.1 is demonstrated, which attains a narrow full width at half maximum of ≈17 nm, fourfold increased maximum current efficiency of 48.9 cd A−1, and 19‐fold improved half‐lifetime of 253.8 h at 1000 cd m−2 compared to a conventional phosphorescent OLED. The findings can lead to better understanding of the hyperfluorescent OLEDs with high performance.

Metal halide perovskite light-emitting diodes (PeLEDs) have gained significant interest for next-generation optoelectronic devices, since PeLEDs exhibit narrow emission bandwidth that allows for vivid and clear images based on their high color purity. [1][2][3][4][5][6] The emission color of PeLEDs is tunable in the visible and near-infrared (NIR) spectral regions and they offer low operating and turn-on voltages, along with promising efficiency values. [3,4,[7][8][9] In addition, thin films have shown nearunity photoluminescence quantum yield (PLQY) and population inversion at room temperature, [10][11][12][13][14] potentially allowing for electrically pumped lasers with various emission colors.There has recently been rapid growth in the external quantum efficiency (EQE) of PeLEDs, to values of over 20%, [9,[15][16][17][18][19][20][21][22][23][24][25][26][27] since early reports of PeLEDs in 2014 with efficiency below 0.25%. [28] Numerous strategies to improve the EQE of PeLEDs are being actively pursued in order to bring their performance in line with other, more established, LED technologies. [8] However, a disparity of refractive index (n) between organic transport layers (typically in the range of 1.6-1.8) and the perovskite emissive layer (≈2.3 near the emission wavelength) holds back performance. [29][30][31][32] Due to the high n of the perovskite layer, the maximum EQE of PeLEDs is limited by outcoupling efficiency and restricted to ≈20%, with the remainder of light being trapped within the thin film and substrate materials, as well as parasitic absorption. [31,32] Therefore, it is necessary to investigate alternative device architectures that are able to enhance outcoupling efficiency and realize direct benefits to EQE.In this study, we demonstrate EQE of 14.6% in methylammonium lead iodide (MAPbI 3 ) based red/NIR LEDs using a randomly distributed nanohole array (NHA) embedded in a SiN layer between the indium tin oxide (ITO) anode and glass substrate. The SiN layer with a high n of 2.02 at the peak emission wavelength possesses a high-index contrast with the voids of the NHA with n of 1.0. This layer effectively compensates for the high n of the perovskite emissive layer and aids outcoupling of waveguided and substrate modes. As a result, PeLEDs with NHAs show 1.64 times higher light extraction than PeLEDs without NHAs. Figure 1a displays the device structure of PeLEDs with and without NHAs, as well as the molecular structures of transport Organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) are promising for next-generation optoelectronic devices due to their potential to achieve high color purity, efficiency, and brightness. Although the external quantum efficiency (EQE) of PeLEDs has recently surpassed 20%, various strategies are being pursued to increase EQE further and reduce the EQE gap compared to other LED technologies. A key point to further boost EQE of PeLEDs is linked to the high refractive index of the perovskite emissive layer, leading to optical losses of more than 70% of ...

Novel homoleptic cyclometalated Ir(III) complexes are designed to improve their emission dipole orientations in the emitting layer of blue phosphorescent organic light emitting devices. Biphenyl group is introduced into the imidazole of cyclometalated Ir(III) complexes to simultaneously achieve enhanced efficiency and operation lifetime, resulting in one of the best device performances of single‐stacked organic light emitting diodes with 91% emission dipole orientation, 26.3% maximum external quantum efficiency (maximally calculated as 41%), and 169 h lifetime at 1000 cd m−2 (LT80), color coordinate (0.17, 0.30). To elucidate the physical origin of this significant improvements, the orientational and positional distributions of the homoleptic dopants are analyzed with consideration on intermolecular interactions through atomistic modeling of the emitting layer. With the findings, the phosphorescent dopants could be designed in the future to achieve enhanced performance.

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