Metal halide perovskite nanocrystals (NCs) have been established as promising materials for light-emitting devices (LEDs) due to their interesting optoelectrical properties, including high photoluminescence quantum yield (PLQY) and high color purity with narrow full width at half maximum (FWHM). However, blue perovskite LEDs, with an emission wavelength below 470 nm, require further investigation to improve their performance. Here, we demonstrated that mixed-halide CsPb(Cl/Br) 3 NCs prepared by ligand exchange with the rigid bidentate structure of adamantane-1,3-diamine (ADDA) can be used for blue LEDs. The ligand exchange of CsPb(Cl/Br) 3 NCs with ADDA improved PLQY without changing the peak wavelength and FWHM. The LEDs based on ligand exchange NCs with ADDA showed an external quantum efficiency (EQE) of 0.49%. Moreover, we also investigated a quaternary ammonium salt, oleylammonium chloride (OAM-Cl), as an interfacial layer to reduce current density. The LED fabricated with OAM-Cl reached an EQE of 1.1% and luminance of 43.2 cd m -2 at the EL wavelength of 456 nm, representing significantly higher performance compared to that of LEDs without OAM-Cl layers. Therefore, the ligand exchange of NCs This article is protected by copyright. All rights reserved.with ADDA and the use of a passivation layer comprising OAM-Cl, facilitate an improvement in the LED performance.

The surface modification of metal halide perovskite nanocrystals (NCs) significantly impacts their optical properties and colloidal stability. This subsequently affects the performance of light-emitting devices (LEDs). Therefore, numerous surface passivation techniques like ligand exchange and metal halide doping have been explored to passivate the surface defects of perovskite NCs and obtain highly efficient LEDs. In this study, we demonstrated the postsynthetic metal halide doping treatment using lead(II) bromide (PbBr 2 ) to passivate the surface defects of the CsPbBr 3 NCs at a moderate reaction temperature of 80 °C. The alkyl quaternary ammonium salt, didodecyldimethylammonium bromide (DC 12 AB), enabled the complete dissolution of PbBr 2 in a nonpolar solvent, toluene. Because of surface crystal growth, the particle sizes of the PbBr 2 -doped CsPbBr 3 NCs were higher than those of the as-synthesized CsPbBr 3 NCs. The photoluminescence quantum yield of the CsPbBr 3 NCs drastically increased from 26.8 to 83.9% after the PbBr 2 doping treatment. Moreover, the PbBr 2 -doped CsPbBr 3 NCs possessed long-term colloidal stability of more than 2 months that indicates the strong bonding between the NCs and ligands. We observed that the alkyl chain length of the quaternary alkyl ammonium salts affected the luminance and device stability during operations. In this study, a promising strategy was devised to achieve highly luminescent perovskite NCs with excellent colloidal stability that can enhance the performance of LEDs.

Robots that simulate patients suffering from joint resistance caused by biomechanical and neural impairments are used to aid the training of physical therapists in manual examination techniques. However, there are few methods for assessing such robots. This article proposes two types of assessment measures based on typical judgments of clinicians. One of the measures involves the evaluation of how well the simulator presents different severities of a specified disease. Experienced clinicians were requested to rate the simulated symptoms in terms of severity, and the consistency of their ratings was used as a performance measure. The other measure involves the evaluation of how well the simulator presents different types of symptoms. In this case, the clinicians were requested to classify the simulated resistances in terms of symptom type, and the average ratios of their answers were used as performance measures. For both types of assessment measures, a higher index implied higher agreement among the experienced clinicians that subjectively assessed the symptoms based on typical symptom features. We applied these two assessment methods to a patient knee robot and achieved positive appraisals. The assessment measures have potential for use in comparing several patient simulators for training physical therapists, rather than as absolute indices for developing a standard.

Metal halides doping of perovskite nanocrystals (NCs) has been shown to precisely control nonradiative pathways and to improve photoluminescence quantum yield (PLQY). Here, we report a trivalent lanthanide halide neodymium (III) chloride (NdCl3)-doped perovskite NCs prepared with a post-synthetic room temperature treatment for efficient blue light-emitting devices (LEDs). The Nd 3d and Cl 2p core peaks were observed in the NdCl3-doped NCs, which allowed for simultaneous doping of Nd3+ and Cl– into the pristine CsPbBr3 NCs. The NdCl3-doped NCs exhibited blue emission at a peak wavelength of 478 nm with a high PLQY of 97% in solution. We found that the Nd3+ cation incorporated into the NCs more effectively suppressed nonradiative recombination compared with common halide anion exchange from temperature dependence of optical properties. Blue LEDs based on NdCl3-doped NCs had an external quantum efficiency of 2.7%, which represents a considerable performance improvement compared with LEDs based on organic chloride salt-doped NCs.

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