A new series of strongly greenish-blue to blue emitting Cu(NN)(POP) + (POP = bis[2-(dipenylphosphino)phenyl]ether) complexes containing N-linked 2-pyridyl pyrazolate diimine ligands [Cu(pypz)(POP)]BF 4 (1), [Cu(pympz)(POP)]BF 4 (2), and [Cu(pytfmpz)-(POP)]BF 4 (3) (pypz = 1-(2-pyridyl)pyrazole, pympz = 3-methyl-1-(2-pyridyl)pyrazole, and pytfmpz = 3-trifluoromethyl-1-(2-pyridyl)pyrazole) have been designed and synthesized. Their structural, electrochemical, and photophysical properties have been characterized. The complexes 1−3 exhibit high photoluminescence quantum yields (PLQYs) at room temperature both in nitrogen-saturated CH 2 Cl 2 (up to 45%) and in neat solid (up to 87%), which are comparable to the reported highest values for the cuprous complexes. The temperature dependence of spectroscopic properties and emission decay behaviors reveal the presence of two thermally equilibrated emitting states. At temperatures below 150 K, the lowest triplet state (T 1 ) is the predominant emitting state resulting in the typical phosphorescence with the emission decay times in the order of hundreds of microseconds. However, at ambient temperature, the lowest singlet state (S 1 ), which lies only about 0.17−0.18 eV above the T 1 state, is populated thermally and in turn generates efficient thermally activated delayed fluorescence (TADF), and the emission decay times are reduced dramatically to, e.g., 12.2 μs for 2. Solution-processed OLEDs containing 1−3 in the emissive layer demonstrated excellent device performances by taking advantage of the singlet harvesting mechanism, among which the electroluminescent device using 3 shows a peak external quantum efficiency (EQE) of 8.47%, a peak current efficiency (CE) of 23.68 cd/A, and a maximum brightness of 2033 cd/m 2 .

Vibration sensor is very necessary for monitoring the structural health of constructions. However, it is still a major challenge to meet simultaneously real-time monitoring, continuous assessment, and early incident warning in a simple device without a complicated power and analysis system. Here, we report a selfpowered vibration sensor system to achieve real-time and continuous detection of the vibration characteristics from a dual-mode triboelectric nanogenerator (AC/DC-TENG), which can produce either alternating current (AC) or direct current (DC) within different operation zones. Within the vibration-safe region, the AC/DC-TENG with AC output not only can continuously assess the vibration characteristics but also can power the signal transmission. More importantly, once the vibration amplitude crosses the danger threshold, the AC converts immediately to DC, meanwhile triggering the alarm system directly to accurately predict the danger of construction. Our self-powered vibration sensor system can serve as a facile tool for accurately monitoring the structural health of constructions.

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