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Aphids use their visual systems to detect information about the external environment, and visual genes are likely to have a role in host plant searching and environmental adaptation. Yet, there is little understanding of the presence and expression of visual opsin genes in aphids. In this study, we cloned and identified four vision-related genes ( LW- OPN, UV- OPN1, UV- OPN2, and rhodopsin) from a cosmopolitan serious cereal pest, Rhopalosiphum padi (L.) ( Hemiptera: Aphididae), and evaluated their expression patterns. Transcription of the four genes was detected at all developmental stages. The inducing conditions (short photoperiod and low temperature) significantly affected the expression of the UV- OPN1 and rhodopsin genes. The highest levels of transcription of all genes were observed in males, and the lowest in oviparae. The expression levels in wingless virginoparae were markedly lower than those in gynoparae and winged virginoparae. The starvation treatments resulted in a decline in the survivorship of adults. The mortality rates increased with increasing duration of starvation. The four genes tended to be upregulated following starvation for 24 h, and their expression levels were considerably decreased after subsequent feeding. These results are of importance for further understanding the evolution and function of visual opsins in aphids. [ABSTRACT FROM AUTHOR]

The different life cycles of aphid species make these organisms good models for studying the short-term consequences of sex. The bird cherry-oat aphid Rhopalosiphum padi has a wide geographic distribution and correspondingly different life cycles. In this study, the life cycles of R. padi collected from six different regions in China were characterized experimentally by comparing the responses of holocyclic and anholocyclic populations to low-temperature and short-photoperiod induction. Clones collected from Chuzhou, Taian, and Taigu consistently reproduced via obligate parthenogenesis, whereas clones from Hami and Baicheng were holocyclic in their response, and those from Lanzhou were both holocyclic and anholocyclic. Prolonged exposure to low temperature and a short photoperiod ( LS) had negative effects on the offspring of anholocyclic aphids with regard to adult lifespan, total longevity, and fecundity compared with aphids maintained at a normal temperature and a long photoperiod ( NL). Holocyclic LS R. padi had longer developmental times at all nymph stages, a shorter adult lifespan, shorter total longevity, and a lower fecundity than NL counterparts. The adult prereproduction period of gynoparae was significantly longer than that of virginoparae, and the total longevity of gynoparae was significantly shorter than that of virginoparae. Moreover, the net reproductive and gross reproduction rates, as well as the total fecundity, were roughly fivefold higher in virginoparae than in gynoparae, indicating that there is the short-term cost of sex. When maintained on their secondary host ( Triticum aestivum), gynoparae, males, and oviparae produced by holocyclic populations could survive, and gynoparae produced oviparae. However, under NL conditions, oviparae could not produce overwintering eggs on the secondary host, whereas a few overwintering eggs were generated by oviparae under LS conditions. Taken together, these results illuminate the complexity of insect responses and contribute to a complete understanding of the aphid life cycle and its evolution. [ABSTRACT FROM AUTHOR]

Highly efficient charge carrier injection from electrodes is basically required for high-performance organic light-emitting diodes (OLEDs). However, the mismatch of metal work function and energy level of charge carrier transport layers inevitably introduces the injection barrier and also greatly restricts the choice of the electrode metals. Here, a planar organic heterojunction (OHJ) C70/pentacene is used as charge generator to realize the highly efficient injection of charge carriers in OLEDs, not only achieving the high efficiency but also significantly improving the stability. More importantly, the resulting devices show an electrode work function-independent efficiency property, greatly broadening the selectivity of electrode metals. Detailed studies are presented on the transport properties of electrons and holes in single-carrier devices based on C70/pentacene OHJ by current density-voltage ( J-V) measurements at various temperatures. It can be seen that Fowler-Nordheim (F-N) tunnel model can be used to well demonstrate the J-V properties, indicating that the charge injection based on OHJ is a tunnel process. The impedance measurements found that the lower lowest unoccupied molecular orbit energy level and higher electron mobility properties are very necessary for the used electron-transport materials to reduce the space charge region width, thus realizing highly efficient electron injection. [ABSTRACT FROM AUTHOR]

The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), is an important pest insect of wheat, Triticum aestivum (L.), in China. The susceptibility and resistance of wheat cultivars to different populations of R. padi have been rarely reported. In the current study, eight R. padi populations were collected from different provinces of China, the resistance or susceptibility of six wheat cultivars (Emai 596, Emai 18, Emai 251, Zhengmai 98, Xanthus and 35A9B) to these eight populations was tested by the ratio of aphid abundance according the standard method previously reported. The results showed that R. padi populations from Lanzhou of Gansu Province and Taian of Shandong Province showed similar pattern of aphid-host reactions among the six wheat cultivars. Populations from Nanyang of Henan Province and Baicheng of Jilin Province shared a different pattern of reaction. The respective populations from Xianyang of Shaaxi Privince, Beibei of Chongqing Province, Hongtong of Shanxi Province and Baoding of Hebei Province showed unique resistance/susceptible patterns of aphid-host reactions from other populations. The variability in the response to wheat cultivars to R. padi indicated the existence of biotypic variation in populations. The weight of adult aphid survivors of different populations varied on six wheat cultivars, but did not correspond well to the susceptibility and resistance of wheat cultivars. Our findings are important for the sustainable control of R. padi in different wheat growing regions of China . [ABSTRACT FROM AUTHOR]

Polycyclic heteroaromatics (PHAs) are a highly versatile class of functional materials, especially applicable as efficient luminophores in organic light‐emitting diodes (OLEDs). Those constructed by tethered phenyl surrounding the main group center attract extensive attention due to their excellent OLED device performance. However, the development of such a class of emitters is often limited to boron, nitrogen‐doped π‐conjugated heterocycles. Herein, we proposed a novel kind of blue emitter by constructing a donor‐acceptor molecular configuration, utilizing a dual sulfone‐bridged triphenylamine (BTPO) core and mono/di‐diphenylamine (DPA) substituents. The twisted D−A molecular structures and appropriate donor strength facilitate the effective separation of natural transition orbitals, endowing the emitters with charge‐transfer dominant hybridized local and charge‐transfer characteristics for the excited states. Both BTPO‐DPA and BTPO‐2DPA own small S1–T1 splitting energy, thus demonstrating blue thermally activated delayed fluorescence. The more symmetrical structure and enhanced CT features brought by additional DPA moiety confer BTPO‐2DPA with a shorter delayed fluorescence lifetime, a higher fluorescence quantum yield and narrower emission. Therefore, BTPO‐2DPA based OLED devices exhibit superior blue electroluminescence performance, with external quantum efficiencies reaching 12.31 %. [ABSTRACT FROM AUTHOR]

Emitters with a hot exciton mechanism are regarded as one of the most promising candidates for organic light‐emitting diodes (OLEDs). In this study, a deep‐blue emitter with the hot exciton mechanism is reported, namely 2An‐PCz, by integrating a pair of carbazole groups with a 9,9′‐bi‐anthracene nucleus. Owing to the symmetric molecular architecture and intrinsic local excited state character, multiple high‐lying reverse intersystem cross (hRISC) channels and large overlaps of frontier molecular orbits (FMOs) can be formed, facilitating rapid hRISC processes as well as enhancement of radiative transition rates simultaneously. Combined with the strong luminescence properties brought by the unique X‐packing mode, a high photoluminescence quantum yield of 60.5% is achieved in the non‐doped state. Strikingly, non‐doped deep‐blue OLEDs exhibited a maximum external quantum efficiency (EQE) of 10.50% with minimal efficient roll‐off, which is one of the highest values for deep‐blue organic light‐emitting devices based on hot exciton emitters thus far. The magneto‐electroluminescence (MEL) experiment and transient electroluminescence measurements corroborated that both the high EQE and suppressed efficiency roll‐off are attributable to the rapid "hot exciton" channels. [ABSTRACT FROM AUTHOR]

Heavy‐metal‐free pure organic room temperature phosphorescence (ORTP) holds great potential in the field of organic optoelectronic devices owing to low economic cost, simple preparation techniques, and high exciton utilization. However, it is still filled with challenges in realizing high efficiency organic light‐emitting diodes (OLEDs) and exploring the internal physical mechanism based on these ORTP molecules. Here, a high‐performance OLED induced by an unexpected interfacial spin‐mixing process between the ORTP molecule and interlayers is demonstrated, and the high efficiency electroluminescence (EL) mechanism is studied through magneto–electroluminescence (MEL) and magneto–photoluminescence (MPL) measurements. The steady‐state and transient PL properties imply that the interfacial effect is related to a high‐lying singlet fission (HLSF) process in the ORTP molecule itself. Further, the HLSF process and the corresponding energy level position are confirmed by the incident wavelength‐ and temperature‐dependent PL spectra and the magnetic‐field‐dependent transient PL. Finally, by optimizing the interfacial material adjacent to the emissive layer to utilize this interfacial spin mixing effect, a high‐efficiency non‐doped ORTP‐OLED with external quantum efficiency of 16% and CIE coordinates of (0.27, 0.49) is developed. The proposed mechanism during the EL process will give insight to produce more efficient OLEDs based on ORTP materials in the future. [ABSTRACT FROM AUTHOR]

Currently, much research effort has been devoted to improving the exciton utilization efficiency and narrowing the emission spectra of ultraviolet (UV) fluorophores for organic light‐emitting diode (OLED) applications, while almost no attention has been paid to optimizing their light out‐coupling efficiency. Here, we developed a linear donor‐acceptor‐donor (D–A–D) triad, namely CDFDB, which possesses high‐lying reverse intersystem crossing (hRISC) property. Thanks to its integrated narrowband UV photoluminescence (PL) (λPL: 397 nm; FWHM: 48 nm), moderate PL quantum yield (ϕPL: 72 %, Tol), good triplet hot exciton (HE) conversion capability, and large horizontal dipole ratio (Θ//: 92 %), the OLEDs based on CDFDB not only can emit UV electroluminescence with relatively good color purity (λEL: 398 nm; CIEx,y: 0.161, 0.040), but also show a record maximum external quantum efficiency (EQEmax) of 12.0 %. This study highlights the important role of horizontal dipole orientation engineering in the molecular design of HE UV‐OLED fluorophores. [ABSTRACT FROM AUTHOR]

In the advancement of organic photovoltaics (OPV) toward scale‐up production, how to mitigate the batch instability of electron‐donating polymers originated from varied molecular weights remains a great challenge. By taking into consideration the relationship between the molecular weight of electron‐donating polymers and the relevant critical concentration (c*) of the solution, herein it is demonstrated that the aggregation behavior of the electron‐donating polymers can be tailored through manipulating c* of the polymer solution. It is interesting to note that the excessive aggregation in low‐molecular‐weight fractions can be circumvented while the favorable mixing ratio can be identified. By preparing the binary bulk heterojunction film under c*‐defined conditions for mixed‐molecular‐weight polymers, a notable power conversion efficiency of 19.1% for binary devices is achieved. Of particular importance is that a linear interrelation can be established between the c* for the maximum PCE and c* for the low‐molecular‐weight fraction aggregation, validating those straightforward spectra measurements can accurately and rationally guide the molecular weight mixing of photovoltaic donor polymers, thereby fully harnessing the potent driving force and affinity inherent to the low‐molecular‐weight fractions. These findings offer a straightforward and logical framework for addressing batch variability in the large‐scale production of high‐performance OPV devices. [ABSTRACT FROM AUTHOR]

Organic semiconductors with optoelectronic properties have attracted intensive interests in the fields of organic light-emitting diodes, organic photovoltaics and organic photodetectors. In these functional devices, exciton evolution is the key process. Generally, linear process is dominant that one photon is created from each injected electron-hole pair, vice versa. This linear process restricts the internal quantum efficiency to be 100% in optoelectronic devices. Alternatively, nonlinear optoelectronic processes, like triplet-triplet annihilation (TTA) and singlet fission (SF), can theoretically break the limitation stated in linear optoelectronic processes. TTA and SF are two dynamic reversible processes, which link one high-lying energy singlet with two low-lying energy triplet excitons on two neighboring chromophores. These nonlinear processes bring the possibility of novel functions and application scenarios, and hence have attracted more and more attentions recently. This review will systematically and comparatively summarize the basic properties of TTA and SF processes, and their applications in optoelectronic devices in the view of device physics. It starts with a concise introduction of basic knowledge of TTA and SF. Then, the characteristics used to identify these processes are described. Subsequently, implementing them in OLEDs are summarized, followed by the application examples in OPVs. Emphasis is laid on the triplet quenching mechanisms in working devices, since both TTA and SF processes highly rely on triplet excitons. These discussions on the recent important progresses aim to gain some insight into the device physics for device engineering. Finally, a perspective is presented. [ABSTRACT FROM AUTHOR]

It is well known that one of the major challenges facing white organic light‐emitting diodes (WOLEDs) has been to achieve high efficiency, low efficiency roll‐off, and high color rendering index (CRI) simultaneously. A simple charge‐ and exciton‐confining emitting layer structure formed by employing a blue emitting p/n heterojunction, and combined with red, yellow, and green phosphorescent ultrathin layers, is presented, thus realizing the stable utilization of 100% excitons. The resulting hybrid WOLEDs exhibit the maximum forward‐viewing external quantum efficiency and power efficiency of 23.4% and 50.4 lm W−1, and keep them at 20.3% and 31.2 lm W−1 at 1000 cd m−2, showing high efficiency and low efficiency roll‐off. Furthermore, the device also shows extremely stable electroluminescent spectra in the whole luminance range with a high CRI of 93 and the Commission Internationale de L'Eclairage coordinates of (0.49, 0.43) at 1000 cd m−2, which is perfect warm white for indoor lighting. The achievement of the excellent comprehensive performances is the best result reported to date among the conventional blue fluorescence‐based hybrid WOLEDs possessing such high CRI, which may be a new starting point for further research on high‐performance hybrid WOLEDs. [ABSTRACT FROM AUTHOR]

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Herein, a high‐mobility polymer (Si25) pairing a nonfullerene acceptor (O‐IDTBR) is introduced to construct active layers of organic solar cells (OSCs). The OSCs based on Si25 and O‐IDTBR with comparable bandgaps of 1.61 eV show high open‐circuit voltage (Voc) of 1.03 V. Suitable energy level offsets between the donor and acceptor as well as sufficient photon absorbance by a 400 nm thick active layer afford a notable short‐circuit current (Jsc) of 21.11 mA cm−2, indicating a significantly suppressed trade‐off between Jsc and Voc among OSCs. In addition, notable high power conversion efficiency (PCE) between 10.2% and 11.54% can be achieved with thick blend films from 210 to 560 nm, a thickness range beneficial to pin‐hole free printing. The maximum PCE of 11.54% corresponds to a 400 nm thick blend film, which is a rare thickness for high‐efficiency nonfullerene‐based OSCs. The corresponding fill factors (FFs) are between 51.59% and 53.33%. The inferior FF is due to a very low electron–hole mobility ratio, offering space for future FF elevation. The results highlight the high Voc and Jsc potentials for thick‐film nonfullerene OSCs based on a high hole mobility donor as well as looking forward to a high electron mobility nonfullerene acceptor. [ABSTRACT FROM AUTHOR]

The emerging thermally activated delayed fluorescence materials have great potential for efficiencies in organic light-emitting diodes by optimizing molecular structures of the emitter system. However, it is still challenging in the device structural design to achieve high efficiency and stable device operation in white organic light-emitting diodes. Here we propose a universal design strategy for thermally activated delayed fluorescence emitter-based fluorescent white organic light-emitting diodes, establishing an advanced system of "orange thermally activated delayed fluorescence emitter sensitized by blue thermally activated delayed fluorescence host" combined with an effective exciton-confined emissive layer. Compared to reference single-layer and double-layer emissive devices, the external quantum efficiency improves by 31 and 45%, respectively, and device operational stability also shows nearly fivefold increase. Additionally, a detailed optical simulation for the present structure is made, indicating the validity of the design strategy in the fluorescent white organic light-emitting diodes. Demonstrating white organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) emitters with high performance and operational stability remains a challenge. Here, the authors show efficient and stable white OLEDs based on a double-dopant TADF system. [ABSTRACT FROM AUTHOR]

Triplet‐triplet fusion (TTF) can effectively transfer triplet excitons to singlet energy level and exhibit good stability, making it widely used in blue fluorescence organic light emitting diodes (OLEDs) for practical application. However, the efficiency of the resulting blue fluorescence OLEDs is still fundamentally limited. Herein, this work introduces a hot exciton efficiency enhancement layer (EEL) between TTF emissive layer and electron‐transporting layer for the first time. It can be found that the triplet excitons are greatly utilized by the efficient hot exciton EEL. As a result, a high efficiency blue fluorescence OLED is successfully developed, exhibiting a maximum external quantum efficiency of 15.2% at the luminance of 4068.0 cd m−2, achieving a breakthrough in the efficiency of blue TTF‐OLEDs. Transient electroluminescence (TrEL) measurements and detailed theoretical calculations confirm the key role of the effective hot exciton process from the high‐lying triplet energy level (Tn, n ≥ 2) to S1 via a reverse intersystem crossing (hRISC). Furthermore, the device lifetime is also greatly improved owing to the fast and efficient hRISC in the introduced hot exciton EEL. This work has important guiding significance for constructing high efficiency blue fluorescence OLEDs by introducing hot exciton molecules. [ABSTRACT FROM AUTHOR]

Due to the hydrophobic organic cations, quasi‐two‐dimensional (quasi‐2D) lead halide perovskite materials have shown better moisture resistance. However, the inappropriate multiphase structure in the quasi‐2D perovskite films seriously affects the efficient transport of energy from low‐n domains to high‐n domains, especially when prepared in air. Herein, the study develops efficient quasi‐2D perovskite films in 30% ± 10% humidity and studies their amplified spontaneous emission (ASE) properties. It can be seen that the phase disproportionation of the quasi‐2D perovskite films prepared in air is greatly suppressed by manipulating the crystallization kinetics of the multiphase structure via using the organic additive benzimidazole (BI), thereby enabling a narrowed phase distribution. Due to the improvement in energy transfer efficiency, surface roughness, and humidity stability, the ASE with a low threshold of 13.4 µJ cm−2 is realized under the quasi‐continuous pumping condition, which is significantly <28.8 µJ cm−2 of the pristine film. Furthermore, the introduction of BI organic additive enhanced the number of peak intensity half‐decay pulses to as high as 5.6 × 107, indicating a good operating stability of the BI‐treated films. This work suggests that the BI‐treated quasi‐2D perovskite films provide the possibility for preparing high‐performance lasers in air. [ABSTRACT FROM AUTHOR]

It is still challenging to achieve blue OLEDs with sufficient color purity, lifetime and efficiency for applications. Thermally activated delayed fluorescence (TADF) materials become the most promising. However, the internal mechanism of the efficiency roll-off and long-term stability degradation still needs deep research. In this work, the energy transfer and exciton quenching processes in TADF-based blue OLEDs were analyzed under steady-state conditions and their relative contributions to efficiency roll-off were quantified. Furthermore, the degradation mechanism in the TADF-based blue OLEDs was investigated both theoretically and experimentally by a comprehensive exciton quenching model. It was demonstrated that suppressing the triplet–polaron annihilation processes and reducing the accumulation of triplet excitons through reasonable energy transfer can decrease the effect of exciton quenching, thereby significantly reduce the efficiency roll-off and improve device lifetime. It can be seen that the external quantum efficiency (EQE) of the resulting blue OLEDs was enhanced to 30.3 % with CIE coordinates of (0.16, 0.25) and kept 20.9 % at the luminance of 1000 cd/m2. More importantly, the device lifetime was also significantly enhanced, which is over three times longer than that of the unoptimized devices due to the suppress of triplet-polaron annihilation and triplet accumulation. Reducing the accumulation of triplet excitons through reasonable energy transfer can suppress the triplet–polaron annihilation processes, and significantly reduce the efficiency roll-off and improve device lifetime. [Display omitted] • The energy transfer, exciton quenching processes and degradation mechanism in TADF-based blue OLEDs were analyzed. • The degradation mechanism in the TADF-based blue OLEDs was investigated both theoretically and experimentally by a comprehensive exciton quenching model. • The EQE of the OLEDs was enhanced to 30.3 %. • The lifetime of the OLEDs was enhanced due to the suppress of triplet-polaron annihilation. [ABSTRACT FROM AUTHOR]

The development of lasing materials with weak pile‐up effect from triplet excitons, low lasing threshold, and long operational lifetime is much significant for truly continuous wave operation and electrically pumping organic lasers. However, most of organic gain media has been verified to have extreme quenching effect from triplet excitons due to its wide‐band distribution of triplet absorption spectrum. Here, it is found that the phenanthroimidazole derivatives as gain media have congenital advantages on handling triplet's issues. A very low amplified spontaneous emission (ASE) threshold of 0.56 µJ cm−2 and a long operational lifetime of 5.77 × 105 pump pulses in air atmosphere are well obtained. When increasing the pump repetition frequency from 20 Hz to 20 kHz, the operational lifetimes of the thin films have small reduction. Under a high pump repetition frequency of 200 kHz, which is quasi‐continuous wave operational regime, the PI2PhDPO thin film exhibits very low ASE threshold of 0.78 µJ cm−2 due to the tiny overlap between triplet absorption and ASE spectra. [ABSTRACT FROM AUTHOR]

Abstract High efficiency all fluorescent white organic light-emitting diodes (WOLEDs) based on yellow fluorescent guest doped blue exciplex host as the emitting layer (EML) are fabricated by inserting a thin hole-transporting layer (HTL) in EML. It is found that the thin HTL forms an additional interface exciplex in EML, as a result, the efficiency and efficiency roll-off at high luminance are greatly improved by the efficient exciton control via the interface exciplex. The resulting WOLEDs show the maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 32.6 cd/A, 35.9 lm/W and 10.1%, respectively, and 25.6 cd/A, 16.1 lm/W and 8.1% at 1000 cd/m2 luminance, indicating the effectiveness of this interface exciplex structure to achieve remarkable efficiency all fluorescent WOLEDs. Graphical abstract High efficiency all fluorescent WOLEDs based on yellow fluorescent guest doped in blue exciplex host are fabricated, and a thin hole-transporting layer is inserted in EML to form interface exciplex to realize efficient exciton control and energy transfer in the EML. Image 1 Highlights • High efficiency all fluorescent WOLEDs are successfully fabricated. • Interface exciplex forms in EML to realize energy transfer effectively. • Realized low efficiency roll-off through EML structure design. [ABSTRACT FROM AUTHOR]

Excellent stability is an essential premise for organic diradicals to be used in organic electronic and spintronic devices. We have attached two tris(2,4,6‐trichlorophenyl)methyl (TTM) radical building blocks to the two sides of perylene bisimide (PBI) bridges and obtained two regioisomeric diradicals (1,6‐TTM‐PBI and 1,7‐TTM‐PBI). Both of the isomers show super stability rather than the monomeric TTM under ambient conditions, due to the increased conjugation and the electron‐withdrawing effects of the PBI bridges. The diradicals show distinct and reversible multistep redox processes, and a spectro‐electrochemistry investigation revealed the generation of organic mixed‐valence (MV) species during reduction processes. The two diradicals have singlet ground states, very small singlet–triplet energy gaps (ΔES‐T) and a pure open‐shell character (with diradical character y0=0.966 for 1,6‐TTM‐PBI and 0.967 for 1,7‐TTM‐PBI). This work opens a window to developing very stable diradicals and offers the opportunity of their further application in optical, electronic and magnetic devices. [ABSTRACT FROM AUTHOR]

High‐quality near‐ultraviolet/deep‐blue organic emitters are urgently needed but still rare. Here, three V‐shape donor‐acceptor‐donor (D‐A‐D) emitters based on pyrazine cores, namely, VDMP‐PhCz, VDMP‐36PhCz, and VDMP‐TPA, are designed and synthesized. Their doped devices using a high‐polar host show remarkable electroluminescence (EL) performances with maximum external quantum efficiency (EQE) values up to 7.37%, 7.55%, and 9.03%, and corresponding CIE coordinates of (0.160,0.040), (0.161,0.039), and (0.149,0.072), respectively. Supported by theoretical calculations and experimental results, the high EL performances of these emitters are achieved by their planarized intramolecular charge transfer (PLICT) features, high triplet‐excitons utilization from "hot exciton" channels, and high horizontal dipole orientations. Furthermore, these PLICT‐based emitters can also function as efficient hosts for green or yellow multi‐resonance (MR) narrowband emissive guests, providing high EQEs of over 32% with alleviated efficiency roll‐offs. [ABSTRACT FROM AUTHOR]

The pursuit for efficient deep blue material is an ever‐increasing issue in organic optoelectronics field. It is a long‐standing challenge to achieve high external quantum efficiency (EQE) exceed 10% at brightness of 1000 cd m−2 with a Commission International de L'Eclairage (CIEy) <0.08 in non‐doped organic light‐emitting diodes (OLEDs). Herein, this study reports a deep blue luminogen, PPITPh, by bonding phenanthro[9,10‐d]imidazole moiety with m‐terphenyl group via benzene bridge. The non‐doped OLED based on PPITPh exhibits an exceptionally high EQE of 11.83% with a CIE coordinate of (0.15, 0.07). The EQE still maintains 10.17% at the brightness of 1000 cd m−2, and even at a brightness as high as 10000 cd m−2, an EQE of 7.5% is still remained, representing the record‐high result among non‐doped deep‐blue OLEDs at 1000 cd m−2. The unprecedented device performance is attributed to the reversed intersystem crossing process through hot exciton mechanism. Besides, the maximum EQE of orange phosphorescent OLED with PPITPh as host is 32.02%, and remains 31.17% at the brightness of 1000 cd m−2. Such minimal efficiency roll‐off demonstrates that PPITPh is also an excellent phosphorescent host material. The result offers a new design strategy for the enrichment of high‐efficiency deep blue luminogen. [ABSTRACT FROM AUTHOR]

"Hot exciton" molecules that allow the transition of excitons from a high‐lying triplet state (Tn, n≥ 2) to singlet states (Sm, m≥1) by a reverse intersystem crossing (hRISC) process have become an effective strategy to achieve high efficiency fluorescence organic light emitting diodes (OLEDs). However, the understanding of the dynamic behavior of the "hot exciton" process is still very lacking. Herein, the exciton dynamics of an aggregation‐induced emission (AIE) molecule TPA‐An‐mPhCz with the "hot exciton" property are deeply investigated, and the proportion between hRISC and internal inversion (IC) of excitons on Tn is successfully quantified by in situ transient electroluminescent measurements and theoretical calculation. It is found that the IC process increases severe energy loss of Tn excitons. By introducing a triplet–triplet annihilation up‐conversion layer in the emissive layer to efficiently recapture the IC excitons and further doping a blue fluorescent emitter in the TPA‐An‐mPhCz layer to achieve high photoluminescence quantum yield (PLQY), the resulting OLED achieves a maximum external quantum efficiency of 12.5% with negligible efficiency roll‐off. More impressively, the operational lifetime LT75 (lifetime to 75% of the initial luminance) of the device with efficient triplets utilization performs a remarkable 116 h under 1000 cd m−2. This work provides the fundamentals for the design of hot exciton materials with efficient exciton utilization to develop efficient blue fluorescence OLEDs. [ABSTRACT FROM AUTHOR]

Utilizing exciplex as the host and fluorescence emitter with dopant materials has been proved successfully to fabricate highly-efficient organic light-emitting diodes. Exciton evolution and energy transfer in this exciplex host–guest system are complex. Gaining insight into the electroluminescence (EL) mechanisms in exciplex-based devices is key for further optimizing device configuration. Here, we have investigated exciton dynamics in devices with exciplex as host and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) as red fluorescence emitter. Two exciplexes, 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPY) doped 2,4,6-tris[3-(triphenylphosphine)phenyl]-1,3,5-triazine (POT2T), and 4,4′,4″-tris[3-methylphenyl(phenyl)amino]-triphenylamine (m-MTDATA) doped tris(8-hydroxyquinoline)aluminum(III) (Alq3), with different band energy are utilized as host materials. Combining the measurements of transient EL, transient photoluminescence and magnetic field effect (MFE), it is concluded that Dexter energy transfer, together with Förster resonance energy transfer, are confirmed in the pure fluorescence doped system. Meanwhile, it is found that DCJTB works with the hot excitons mechanism but not a traditional red fluorescence emitter as recognized previously. This work presents that the transient MFE is powerful for detecting excitonic dynamic processes in excipelx based host–guest EL systems. [ABSTRACT FROM AUTHOR]

Rhopalosiphun padi is a pest that seriously devastates wheat crops. The life cycle, genetic diversity, and genetic structure of R. padi populations throughout China remain unclear. In the current study, we collected 17 R. padi populations throughout the wheat-growing region of China. Classical standard methods were used to determine the life cycles of 369 clones from the sampled populations. Five polymorphic microsatellite loci were used to genotype individuals from each clone. The results revealed that two populations from spring wheat-growing regions showed cyclical parthenogenesis, whereas 15 populations from winter wheat-growing regions showed obligate parthenogenesis. There was a significant genetic difference between populations with obligate parthenogenesis and populations with cyclical parthenogenesis. Populations with cyclical parthenogenesis did not show significant departures from Hardy-Weinberg equilibrium, whereas all populations with obligate parthenogenesis exhibited significant departures from Hardy-Weinberg equilibrium. Significant genetic structures were found in the populations. Two R. padi populations with cyclical parthenogenesis showed similar genetic structures, two populations from a subtropical plateau had similar genetic structures, and the populations sampled in the large winter wheat-growing regions in northern and central China showed similar genetic structures. There was a significant isolation-by-distance effect present among different populations. To the best of our knowledge, this is the first documentation of the life cycle and population genetic of R. padi in China. Our results are important for the design and optimization of sustainable pest management strategies. [ABSTRACT FROM AUTHOR]

The operational lifetime of blue organic light‐emitting diodes (OLEDs) is still insufficient for practical applications in lighting and display. One type of blue organic emitting materials with hybridized local and charge‐transfer (HLCT) process are beneficial in achieving high‐efficiency OLEDs through "hot exciton" channel by harnessing high‐lying triplet (Tn) excitons. However, the operational lifetime of the resulting blue OLEDs is rarely studied and understood. In this article, the aging properties of blue fluorescent OLEDs based on an HLCT material (2‐(4‐(10‐(3‐(9H‐carbazol‐9‐yl)phenyl)anthracen‐9‐yl)phenyl)‐1‐phenyl‐1H‐phenanthro[9,10‐d]imidazole) (PAC) are systematically investigated by exciton dynamics calculation and transient EL experiments. It is experimentally and theoretically revealed that whether the reverse intersystem crossing (hRISC) process from high‐lying excited triplet to singlet in HLCT materials is completely effective determines the device degradation. A fluorescent emitter is doped into PAC host to accelerate the hRISC process, thus enhancing device operational lifetime to reach T75 = 110 ± 2 h (time to 75% of initial luminance) under 1000 cd m−2. This work provides inspirations to investigate the stability of blue fluorescent OLEDs based on HCLT materials and further enhance the operational lifetime. [ABSTRACT FROM AUTHOR]