Organic mechanoluminochromic materials are mechano/piezo-responsive and promising for applications in sensors, displays, and data storage devices. However, their switching range of emission is seriously impeded by only one kind of emission (either a fluorescent or phosphorescent peak) in the spectrum of single organic compounds. This study presents a design strategy for pure organic compounds with excellent room-temperature fluorescent-phosphorescent dual-emission (rFPDE) properties, which combines the effective factors of dipenylsulfone group, crystalline state, and heavy atom effect. Following the principle of color mixing, myriad emission colors with a wide range from orange to purple and across white zone in a straight line in the chromaticity diagram of the Commission Internationale de l'Eclairage (CIE) can be obtained by simply mechanical grinding the compound. The unique properties could be concentrated on a pure organic compound through this design strategy, which provides a new efficient channel for the discovery of efficient mechano-responsive organic materials.
3268www.MaterialsViews.com wileyonlinelibrary.com reached 90 lm W −1 at 1000 cd m −2 , [ 2 ] which is readily above the effi ciency of a general fl uorescent tube. However, there is still a big room for improvement compared to the theoretical limit of 248 lm W −1 . [ 3 ] Among the three primary colors, effi cient blue light emission is the bottleneck for effi cient full-color OLED display and white OLEDs. [ 4 ] In the past few years, many studies have focused on improving external quantum effi ciency ( h ext ) of blue OLEDs by utilizing a common blue phosphorescent emitter of iridium(III) bis [(4,6-h ext values over 20% have been achieved by developing new materials, such as bipolar host materials and electron-transport materials (ETMs) with high triplet energy level, due to effi cient harvesting of both electro-generated singlet and triplet excitons for phosphorescent emission from OLEDs. [ 1c , 5 ] Most recently, h ext values were further improved to ≈30% by Lee et al. by using a pyrido [2,3-b ] indole derivative as the host material and a 50-nm-ITO-coated glass as the substrate due to the improved carrier balance and light outcoupling. [ 6 ] Aside from the external quantum effi ciency, reducing operating voltage is also crucially important for high power conversion effi ciency. As the most recent report, although h ext value of ≈30% has been achieved, the power effi ciency was compromised by the relatively high driving voltage, giving the maximum power effi ciency ( h P ) of only 50.6 lm W −1 . [ 6b ] Nevertheless, unlike the most intensively investigated EQE, reducing operating voltage without compromising external quantum effi ciency seems to be ignored or underestimated. The limit of operating voltage is generally believed to be equal to the energy band gap ( E g ) of the emitter molecule or the photon energy ( hv ) of the emission light divided by the electron charge ( e ), which is corresponding to the energy difference between the highest occupied molecular orbital (HOMO) and the unoccupied molecular orbital (LUMO). Although a few exceptions were reported, where the devices could even be operated at half of the voltage of E g / e , [ 7 ] the electroluminescence was achieved with an Augerassisted mechanism, and multiple electrons should be used for one photon emission to give a very low h ext of 0.4%.
This study utilized independent component analysis to explore the abnormal functional connectivity (FC) in male participants with Internet gaming disorder (IGD). Functional magnetic resonance imaging and behavioral data were collected from 21 healthy controls (HC) and 18 IGD patients when they were performing a delay discounting task. Behavioral results revealed that the IGD patients showed higher delay discounting rates than HC. Two networks were found to be associated with IGD: (1) the executive control network containing the anterior cingulate cortex and the medial and superior frontal gyrus, and (2) the basal ganglia network containing the lentiform nucleus. Comparing to HC, IGD exhibited stronger FC when selecting small and now options. In addition, the delay discounting rates were positively correlated with the modulation of the two networks and the reaction time. The results suggested that the IGD patients have enhanced sensitivity to reward and decreased ability to control their impulsivity effectively, which leads to myopic decision making.
Although Internet games have been proven to be addictive, only a few game players develop online gaming addiction. A large number of players play online games recreationally without being addicted to it. These individuals are defined as recreational Internet gaming users (RGU). So far, no research has investigated decision-making and impulse control in RGU. In the current study, we used delay discounting (DD) task and probabilistic discounting (PD) task to examine decision-making and impulse control in 20 healthy controls, 20 subjects with Internet gaming disorder (IGD) and 23 RGU during fMRI scanning. At the behavioral level, RGU showed lower DD rate and higher PD rate than subjects with IGD and there was no significant difference between RGU and healthy controls on the DD and PD rates. At the neural level, RGU showed increased neural response in the parahippocampal gyrus, the anterior cingulate cortex, the medial frontal gyrus and the inferior frontal gyrus as compared with subjects with IGD. These brain regions may play an important role in preventing RGU from developing addiction. The results suggest that the RGU are capable of inhibiting impulse due to additional cognitive endeavor and the subjects with IGD have deficit in decision-making and impulsive control, which are associated with brain dysfunction.
A series of blue emitters incorporating spiro[fluorene-9,9′-thioxanthene] or spiro[fluorene-9,9′-thioxanthene-S,S-dioxide] as the core and phenylcarbazole or triphenylamine as the arms were designed and synthesized. Their spiro conformation is beneficial for their thermal stability and for reducing the trend of aggregation quenching. By tuning the valence of the sulfur atom, highly efficient local excited (LE) state deep blue emitters and charge-transfer (CT) state blue emitters are obtained. The devices based on the LE emitters TPA-S and CzB-S as the nondoped emissive layer exhibit high external quantum efficiency of 1.76% and 2.03% and Commission Internationale de l’Eclairage (CIE) coordinates of (0.158, 0.039) and (0.160, 0.054), respectively, and their CIE y values are among the smallest ever reported for the deep blue OLEDs and are readily very close to that of the inorganic light-emitting diode [CIE (0.16, 0.02)]. The nondoped device based on the CT emitter TPA-SO2 as the emissive layer also exhibits a high current efficiency of 5.46 cd A–1 and CIE coordinates of (0.154, 0.168). To fully utilize the 25% singlet and 75% triplet excitons, fluorescent/phosphorescent hybrid white organic light-emitting diodes in a single-emissive-layer architecture were also fabricated with TPA-SO2 as the blue emitter as well as the host of orange phosphorescent emitter to give forward-viewing power efficiency of 47.9 lm W–1, which is the highest value ever reported for the devices in a similar architecture without using any out-coupling technology.
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