White organic light‐emitting diode (WOLED) technology has attracted considerable attention because of its potential use as a next‐generation solid‐state lighting source. However, most of the reported WOLEDs that employ the combination of multi‐emissive materials to generate white emission may suffer from color instability, high material cost, and a complex fabrication procedure which can be diminished by the single‐emitter‐based WOLED. Herein, a color‐tunable material, tris(4‐(phenylethynyl)phenyl)amine (TPEPA), is reported, whose photoluminescence (PL) spectrum is altered by adjusting the thermal annealing temperature nearly encompassing the entire visible spectra. Density functional theory calculations and transmission electron microscopy results offer mechanistic understanding of the PL redshift resulting from thermally activated rotation of benzene rings and rotation of 4‐(phenylethynyl) phenyl)amine connected to the central nitrogen atom that lead to formation of ordered molecular packing which improves the π–π stacking degree and increases electronic coupling. Further, by precisely controlling the annealing time and temperature, a white‐light OLED is fabricated with the maximum external quantum efficiency of 3.4% with TPEPA as the only emissive molecule. As far as it is known, thus far, this is the best performance achieved for single small organic molecule based WOLED devices.

Strain compensation in a Zn doped MAPbBr3 single crystal under light illumination gives rise to improved photostability in terms of temperature and time to the benefit of photodetector.

We investigated the water H-bond network and its dynamics in Ni2Cl2BTDD, a prototypical MOF for atmospheric water harvesting, using linear and ultrafast IR spectroscopy. Utilizing isotopic labeling and infrared spectroscopy, we found that water forms an extensive H-bonding network in Ni2Cl2BTDD. Further investigation with ultrafast spectroscopy revealed that water can reorient in a confined cone up to ∼50° within 1.3 ps. This large angle reorientation indicates H-bond rearrangement, similar to bulk water. Thus, although the water H-bond network is confined in Ni2Cl2BTDD, different from other confined systems, H-bond rearrangement is not hindered. The picosecond H-bond rearrangement in Ni2Cl2BTDD corroborates its reversibility with minimal hysteresis in water sorption.

All‐inorganic perovskite nanocrystals (NCs) have received extensive attention for next‐generation thin film devices due to their excellent optical properties, such as strong light absorption, high carrier mobility, and defect tolerance. However, significant challenges remain to obtain high‐quality perovskite thin films. Herein, a simple but effective post‐treatment by laser irradiation for CsPbBr3 NCs thin films is reported. Laser‐induced secondary crystallization is observed in CsPbBr3 NCs thin films after treatment. In addition, amplified spontaneous emission (ASE) with a low threshold (5.6 µJ cm−2) and a high gain value (743 cm–1) is achieved. Based on optical measurements, it is attributed to the low defect density, reduced Auger recombination, and weak exciton–phonon interactions, which greatly suppress the nonradiative recombination channels. The ASE from the film after treatment has a high characteristic temperature (134 K), showing a stable optical gain performance that maintains its intensity for 35 h at room temperature (and 12 h at 40 °C). Finally, the proof‐of‐concept demonstration of graphic coding is shown. This study deepens the understanding of the optical gain mechanism of CsPbBr3 perovskite films and provides a simple and convenient laser treatment that enables the fabrication of high‐quality CsPbBr3 perovskite thin films.

A highly selective colorimetric and ratiometric “two-stage”/“off-on” type fluorescent probe with the ability to exclude other heavy and transition metal ions has been designed and synthesized. Low concentration of Fe3+...