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 ...

The electrochromic mechanism of IrO 2 thin films was investigated with electrochemical quartz crystal microbalance and surface analyses such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron microscopy. Prior to pulsed anodic current electrodeposition of IrO 2 thin film on indium-tin oxide substrate ͑total anodic charge 100 mC/cm 2 ͒, IrO 2 islands, which work as good adhesive seeds, were prepared by cyclic voltammetry. In phosphate buffered saline solution, IrO 2 exhibited blue and black anodic electrochromic behavior at two oxidation potentials of ϩ0.5 and ϩ0.9 V ͑vs. a saturated calomel electrode͒. Surface analysis and mass variations of IrO 2 thin film indicated that the ejection of H ϩ and the injection of Na ϩ caused the cracks in the film and resulted in coloring behaviors.Electrochromism is the reversible color change of electrochromic materials by applying a small voltage or current and, thus, it has drawn interest for optical devices such as smart windows, automotive mirrors, and light shutters. In electrochromic devices ͑ECDs͒, the selection of electrochromic materials is an important factor for effective coloration bleaching. Two typical electrochromic materials are metal oxides ͑e.g., IrO 2 , 1,2 WO 3 , 3,4 NiO, 5 and V 2 O 5 6 ͒ and conducting polymers ͑e.g., polypyrrole and polythiophene͒. 7,8 Among electrochromic metal oxides, iridium oxide shows a remarkably fast response to anodic coloration and cathodic bleaching, but its electrochromic characteristics have not been studied intensively compared with other metal oxides.Until now, three possible mechanisms of electrochromic reactions on iridium oxides have been reported ͓injection/ejection of ͑1͒ cation or ͑2͒ anion or ͑3͒ small alkali ions 9 ͔In these electrochromic reactions, mention the injection/ejection of H ϩ has been explained as the most reasonable mechanism on electrochromic iridium oxides.Due to the chemically/mechanically unstable features of iridium oxides, electrochromic properties of IrO 2 thin films are dependent on the preparation conditions and the chemical composition of coating solutions. Five different methods of preparing IrO 2 are as follows: ͑i͒ anodically electrodeposited metal oxide films like PbO 2 ; 1,10 (ii) cathodically electrodeposited metal oxide films ͑e.g., Cu 2 O, ZnO, Y 2 O 3 ); 11-14 (iii) activation of iridium metal by potential cycling to form activated iridium oxide films; 15 (iv) reactive sputtering to form sputtered iridium oxide films; 16 and (v) thermal decomposition of iridium salt solution to form thermal iridium oxide films. 17 In this work, we investigated the electrochromism mechanism of electrodeposited IrO 2 thin films via electrochemical and surface characterization using cyclic voltammetry ͑CV͒, pulsed potential method, in situ electrochemical quartz crystal microbalance ͑EQCM͒ measurement, scanning electron microscope ͑SEM͒, augerelectron spectroscopy ͑AES͒, and X-ray photoelectron spectroscopy ͑XPS͒ analysis. ExperimentalElectrochemical preparation of IrO ...

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Surgical clipping of unruptured intracranial aneurysms in elderly group could get it as a favorable outcome in well selected cases.