Cracked tooth syndrome (CTS) is an incomplete fracture of a human tooth that commonly arises from chewing hard foods. Although it is a very common syndrome, CTS is often difficult to diagnose owing to the common small size of tooth cracks. Conventional techniques for the detection of cracks, such as transillumination and radiographic methods, are inaccurate and have poor imaging resolution. In this study, we devise a novel method for the in vivo detection of tooth microcracks by exploiting the mechanoluminescence (ML) phenomenon. ZrO2:Ti4+ (ZRT) phosphor particles are pasted onto suspected regions of tooth cracks and emit cyan-colored light as a result of masticatory forces. Then, a stretchable and self-healable photodetector (PD) array laminated on top of the phosphor particles converts the emitted photons into a photocurrent, which facilitates the two-dimensional mapping of the tooth cracks. Because of the high photosensitivity of the PD, intense ML and small size of ZRT phosphor particles, it is possible to image submicron- to micron-sized cracks with high resolution. Furthermore, the uniqueness of this technique over the conventional techniques stems from the application of a simple optical phenomenon, i.e., ML, for obtaining precise information regarding the locations, depth, and length of tooth cracks.

Inorganic halide perovskite (CsPbX3, X = Cl, Br, and I) nanocrystals (PNCs) have been highly sought-after materials in recent years owing to their numerous applications in optoelectronic devices. One such application is white light generation for displays and low-cost light sources. Nevertheless, the poor structural and chemical stabilities of these NCs under environmental factors, such as moisture and oxygen, hinder the fabrication of white light-emitting devices. The improved stability of halide PNCs has been mainly achieved by encapsulating them in robust matrices such as oxide materials, inorganic glass, and metal–organic frameworks. This review summarizes how various encapsulating strategies improve the structural stability of halide PNCs and preserve their bright luminescence characteristics, which aids in the fabrication of high-power white light-emitting diodes. Considering that the NCs are characterized by an inorganic perovskite core and an organic surface layer, we discuss their various structural and surface aspects in this review.

Quantum dot light-emitting diodes (QLEDs) are promising devices for display applications. Polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) is a common hole injection layer (HIL) material in optoelectronic devices because of its high conductivity and high work function. Nevertheless, PEDOT:PSS-based QLEDs have a high energy barrier for hole injection, which results in low device efficiency. Therefore, a new strategy is needed to improve the device efficiency. Herein, we have demonstrated a bilayer-HIL using VO2 and a PEDOT:PSS-based QLED that exhibits an 18% external quantum efficiency (EQE), 78 cd/A current efficiency (CE), and 25,771 cd/m2 maximum luminance. In contrast, the PEDOT:PSS-based QLED exhibits an EQE of 13%, CE of 54 cd/A, and maximum luminance of 14,817 cd/m2. An increase in EQE was attributed to a reduction in the energy barrier between indium tin oxide (ITO) and PEDOT:PSS, caused by the insertion of a VO2 HIL. Therefore, our results could demonstrate that using a bilayer-HIL is effective in increasing the EQE in QLEDs.