Exciplex system exhibiting thermally activated delayed fluorescence (TADF) holds a considerable potential to improve organic light‐emitting diode (OLED) performances. However, the operational lifetime of current exciplex‐based devices, unfortunately, falls far behind the requirement for commercialization. Herein, rationally choosing a TADF‐type electron acceptor molecule is reported as a new strategy to enhance OLEDs' operating lifetime. A comprehensive study of the exciplex system containing 9,9′,9′′‐triphenyl‐9H,9′H,9′′H‐3,3′:6′,3′′‐tercarbazole (Tris‐PCz) and triazine (TRZ) derivatives clarifies the relationship between unwanted carrier recombination on acceptor molecules, TADF property of acceptors, and the device degradation event. By employing a proposed “exciton recycling” strategy, a threefold increased operational lifetime can be achieved while still maintaining high‐performance OLED properties. In particular, a stable blue OLED that employs this strategy is successfully demonstrated. This research provides an important step for exciplex‐based devices toward the significant improvement of operational stability.

For elucidating the potential of light amplification properties of thermally activated delayed fluorescence materials (TADF), the distributed feedback (DFB) laser devices using DABNA derivatives having a multiple-resonance effect were fabricated....

We studied the photophysical and electroluminescent (EL) characteristics of a series of azaborine derivatives having a pair of boron and nitrogen aimed at the multi-resonance (MR) effect. The computational study with the STEOM-DLPNO-CCSD method clarified that the combination of a BN ring-fusion and a terminal carbazole enhanced the MR effect and spin-orbit coupling matrix element (SOCME), simultaneously. Also, we clarified that the second triplet excited state (T2) plays an important role in efficient MR-based thermally activated delayed fluorescence (TADF). Furthermore, we obtained a blue–violet OLED with an external EL quantum efficiency (EQE) of 9.1%, implying the presence of a pronounced nonradiative decay path from the lowest triplet excited state (T1).

collide, alongside the formation of singlets and quintets, highly reactive "hot" triplets (>5 eV) would unwarrantedly be formed, leading to the rapid degradation of OLEDs. [5] Therefore, the control of overcrowded high-energy triplets has been the most critical issue for OLED research over the last 20 years. [4,[6][7][8] An alternative triplet-excitonic pathway in blue OLEDs is a triplet-triplet upconversion (TTU), which is a well-established solution for practical applications. [9,10] Anthracene derivatives that are a wellknown TTU material for blue OLEDs have the lowest-excited triplet energy level (T 1 ) of around 1.6 eV that is close to half of the singlet excited energy. The collision of the two low-energy triplets produces just enough energy for a singlet generation rather than the formation of a hot triplet that partially decays nonradiatively via a dissociation potential curve. For this reason, blue TTU-OLEDs provide a practical solution. Although the IQE in TTU-OLEDs falls short of 100%, TTU-OLEDs can theoretically gain the high singlet exciton production yield up to 62.5%.Despite the practical use of pure-blue TTU-OLEDs, TTU's underlying mechanism still remains debated with varied viewpoints. First, from the aspect of the exciton formation process, Monkman's group proposed a family of anthracene derivatives featuring high triplet levels (T n ) exceedingly twice the T 1 levels, leading to nearly 62.5% of IQE in OLEDs in 2013. [11,12] Recently, our group has proposed that spin-orbit coupling induced by intramolecular charge-transfer (CT) interaction in anthracene derivatives could facilitate TTU events. [13] Second, from the aspect of device engineering, in 2015, Xiang et al. revealed that the carrier recombination zone in a blue TTU-OLED exists in the emitter layer (EML) close to the interface between the EML and the hole-transport layer (HTL), [14] indicating the benefit from a dense triplet accumulation at the interface. Alternatively, an origin of the sub-bandgap EL in rubrene-based OLEDs was explained as the CT-sensitized TTU generating at the rubrene/ fullerene interface. [14,15] Further, B.-Y. Lin et al. proposed the CT-sensitized blue TTU-OLEDs to reduce a driving voltage. [16] Although the IQE from these CT-sensitized TTU-OLEDs was far from the theoretical limit, it has been suggested that the CT interface can facilitate TTU events at the interface according to the dense triplet accumulation. [14,[16][17][18][19] However, the interfacial CT formation has been claimed as the main reason for Two low-energy triplets can generate one singlet via triplet-triplet upconversion (TTU), and result in an exciton production yield exceeding 25% in conventional fluorescence-based organic light-emitting diodes (OLEDs). In most cases, since such low-energy triplets induce no serious OLED degradation, TTU-OLEDs are the only commercialized blue OLEDs so far. Herein, it is clarified that the charge-transfer (CT) interaction at a hole-transport/ emitter-layer interface is an overlooked pathway to enhance TTU yield s...

The emerging market is currently witnessing the active development of online shopping. This study was conducted to analyze the key factors affecting the intention of customers to purchase in Vietnam. This study is conducted by two methods, including "secondary research method" and "quantitative method" for research. Firstly, the author uses the "secondary research method" to refer to previous academic sources for this research. Secondly, the author collected a sample of 349 volunteers in Vietnam who have an understanding and interest in e-commerce. Perceived Usefulness, Perceived Ease of Use, Perceived Transaction Security are reported to have a positive relationship with online purchase intention. They are significant factors affecting the purchase intention of Vietnamese online customers. Other demographic factors can affect online shopping intention, such as age and income, so research cannot represent all customers. Businesses can use the findings to further understand about emerging markets. This trend is the basis for business managers to develop customer attraction strategies and improve the quality of online shopping services. The potential for online shopping is becoming more attractive, especially in emerging markets. This study is in line with the trend of the online shopping industry. The results of this study can help marketers understand more about customers' intentions, thereby building long-term relationships between businesses and customers.

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Installing a grid-connected rooftop solar system for a household is an important issue; therefore, there are many factors that need to be considered before the installation is decided. The main factors to be noted are the total cost of the installation, the amount of electricity generated as well as the government's support policies for the development of solar energy. This article presents the design, simulation and economic analysis of an 8.36kWp grid-connected rooftop solar power project for a household in Thu Dau Mot City, Vietnam. The study calculates the generated electricity, the efficiency of the Photovoltaic (PV) power system, the ability to reduce the amount of CO2 emitted into the environment and the economic indicators of the project. This research is useful for stakeholders investing in residential rooftop solar PV systems and Vietnam's energy policymakers as well.

In the process of triplet−triplet upconversion (TTU), a bright excited singlet can be generated because of the collision of two dark excited triplets. In particular, the efficiency of TTU is crucial for achieving a high exciton production yield in blue fluorescence organic light-emitting diodes (OLEDs) beyond the theoretical limit. While the theoretical upper limit of TTU contribution yield is expected to be 60%, blue OLEDs with the maximum TTU contribution are still scarce. Herein, we present a proof of concept for realizing the maximum TTU contribution yield in blue OLEDs, achieved through the doping of thermally activated delayed fluorescence (TADF) molecules in the carrier recombination zone. The bipolar carrier transport ability of TADF materials enables direct carrier recombination on the molecules, resulting in the expansion of the recombination zone. Although the external electroluminescence quantum efficiency of OLEDs is slightly lower than that of conventional TTU-OLEDs due to the low photoluminescence quantum yield of the doped layer, the TTU efficiency approaches the upper limit. Furthermore, the operational device lifetime of OLEDs employing TADF molecules increased by five times compared to the conventional ones, highlighting the expansion of the recombination zone as a crucial factor for enhancing overall OLED performance in TTU-OLEDs.