κ‐channel connectivity in cognitive radio networks for bounded tree‐width graphs

Channel connectivity problem in cognitive radio network (CCP in CRN) is to find a channel assignment for secondary users (SUs) such that underlying graph induced by SUs (potential graph) is connected. Channel connectivity problem in CRNs has been proved to be NP‐complete for general graph and remains NP‐complete even if the underlying potential graph is the tree. Fixed parameter tractability of CCP in CRN has been of research interest because of its practicability. In this work, we have proposed novel problem of fixed parameter tractability for κ ‐CCP of CRN (κ ‐CCP in CRN), ie, whether a given CRN remains connected when any of κ −1 channels are reclaimed by primary users, called κ ‐CCP. This is very crucial to check and design an effective channel assignment algorithm that provides connectivity to SUs on channels reclamation by primary users. To our knowledge, fixed parameter tractability of κ ‐CCP in CRNs has not been studied and becoming useful because of development of 5G if the underlying potential graph has bounded tree‐width and number of channels is parameterized. We address κ ‐CCP in CRN and propose an O (α )^{O (α )}n ^{O (1)} time algorithm if the underlying potential graph is bounded by tree‐width and generates a feasible channel assignment under which given CRN is κ ‐channel connected, where α is the number of channels and n is the number of SUs in CRN. We show that the κ ‐CCP is fixed parameter tractable, when underlying potential graph has bounded tree‐width and number of channels is parameterized. To count the different possible potential solution of κ ‐CCP, we propose a polynomial time algorithm for the corresponding enumeration problem (the number of different feasible channel assignments) E n u m ‐κ ‐CCP on the potential graph with bounded tree‐width when the number of channels is bounded by a constant. Through simulation, we have observed that the feasibility of κ ‐CCP highly depends on the available channels at each SU and number of radio present at each SU.     

Closed‐form expressions for the average channel capacity of the α– μ fading model under different adaptive transmission protocols

In this paper,we consider a small‐scale multipath fading channel following the α– μ generalized fading model distribution.We first derive an expression for the amount of fading () for this channel model to show the generalization attribute of this fading model recently reported in the literature. Then, we derive closed‐form expressions for the average channel capacity considering this channel distribution under different adaptive transmission protocols, namely the simultaneous power and rate adaptation protocol, the optimal rate adaptation with fixed power protocol, and the channel inversion with fixed‐rate protocol. All the obtained expressions are in closed‐form and general expressions that can reduce to other channel capacity expressions that are well‐known and to some others that are not known for Rayleigh, Nakagami‐m, and Weibull, as special cases. The derived expressions in this paper are new and have not been previously reported in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

High‐Mobility Air‐Stable Naphthalene Diimide‐Based Copolymer Containing Extended π‐Conjugation for n‐Channel Organic Field Effect Transistors

A high‐performance naphthalene diimide (NDI)‐based conjugated polymer for use as the active layer of n‐channel organic field‐effect transistors (OFETs) is reported. The solution‐processable n‐channel polymer is systematically designed and synthesized with an alternating structure of long alkyl substituted‐NDI and thienylene–vinylene–thienylene units (PNDI‐TVT). The material has a well‐controlled molecular structure with an extended π‐conjugated backbone, with no increase in the LUMO level, achieving a high mobility and highly ambient stable n‐type OFET. The top‐gate, bottom‐contact device shows remarkably high electron charge‐carrier mobility of up to 1.8 cm² V^?1 s^?1 (I_on/I_off = 10⁶) with the commonly used polymer dielectric, poly(methyl methacrylate) (PMMA). Moreover, PNDI‐TVT OFETs exhibit excellent air and operation stability. Such high device performance is attributed to improved π–π intermolecular interactions owing to the extended π‐conjugation, apart from the improved crystallinity and highly interdigitated lamellar structure caused by the extended π–π backbone and long alkyl groups.     

Growth of 1‐eV GaNAsSb‐based photovoltaic cell on silicon substrate at different As/Ga beam equivalent pressure ratios

We report the performance of 1‐eV GaNAsSb‐based photovoltaic samples grown on a Si substrate using molecular beam epitaxy at different As/Ga beam equivalent pressure (BEP) ratios. The light current–voltage curve and spectral response of the samples were measured. The sample grown at an As/Ga BEP ratio of 10 showed the highest energy conversion efficiency with an open circuit voltage (V_OC) of 0.529 V and a short circuit current density of 17.0 mA/cm². This measured V_OC is the highest ever reported value in GaNAsSb 1‐eV photovoltaic cell, resulting in the lowest ever reported E_g/q‐V_OC of 0.50 eV. The increase in the As/Ga BEP ratio also resulted in an increase in the bandgap‐voltage offset value (E_g/q‐V_OC) and a decrease in quantum efficiency up to As/Ga BEP ratio of 18. Copyright © 2015 John Wiley & Sons, Ltd.     

Impact of co‐channel interference on performance of dual‐hop wireless ad hoc networks over α−μ fading channels

In this work, we investigate the performance of a dual‐hop cooperative network over α?μ fading channels with the presence of co‐channel interference (CCI) at both the relay and destination nodes. Amplify‐and‐forward (AF) relaying is considered in the relay node. The upper bound of the signal‐to‐interference‐plus‐noise ratio (SINR) of the dual‐hop relay link is used to determine the system performance. The probability density function (PDF) and the cumulative distribution function (CDF) of the upper bound of the SINR are analyzed. The system performance is determined in terms of the outage and error probabilities. Numerical results are used to present the performance analysis of the system.     

Self‐Assembling Nanotubes Consisting of Rigid Cyclic γ‐Peptides

Self‐assembling cyclic peptide nanotubes (SPNs) have been extensively studied due to their potential applications in biology and material sciences. Cyclic γ‐peptides, which have a larger conformational space, have received less attention than the cyclic α‐ and β‐peptides. The self‐assembly of cyclic homo‐γ‐tetrapeptide based on cis‐3‐aminocyclohexanecarboxylic acid (γ‐Ach) residues, which can be easily synthesized by a one‐pot process is investigated. Fourier transform infrared (FTIR) and NMR analysis along with density functional theory (DFT) calculations indicate that the cyclic homo‐γ‐tetrapeptide, with a non‐planar conformation, can self‐assemble into nanotubes through hydrogen‐bond‐mediated parallel stacking. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) experiments reveal the formation of bundles of nanotubes in CH₂Cl₂/hexane, but individual nanotubes and bundles of only two nanotubes are obtained in water. The integration of TEG (triethylene glycol) monomethyl ether chains and cyclopeptide backbones may allow the control of width of single nanotubes.     

On the analysis of achievable rate for NOMA networks with cooperative users over κ‐μ shadowed fading channels

Cooperative nonorthogonal multiple access (NOMA) system is an effective solution for the fifth generation (5G) wireless mobile communications systems. In this work, the achievable rate analysis of a NOMA communication network with decode‐and‐forward (DF) relaying under κ‐μ shadowed fading conditions is investigated. First, we develop an analytical framework for cumulative distribution function (CDF) of the considered system model. Then, the average achievable rate expressions for two different information bits namely s₁ and s₂ are derived based on the derived CDF for NOMA with DF relaying over κ‐μ shadowed fading channels. Furthermore, we also propose simplified average achievable rate expressions for the special cases of κ‐μ shadowed fading channels in order to facilitate the evaluation of the derived expressions. Some numerical examples on the achievable rate of the considered system are shown for different scenarios. Moreover, our derived analytical average achievable rate expressions are confirmed by the simulations results.     

Novel Ω‐Shaped Core–Shell Photodetector with High Ultraviolet Selectivity and Enhanced Responsivity

The design of nanostructure plays an important role in performance enhancement of low‐dimensional optoelectronic devices. Herein, a novel photodetector (PD) based on electrospun SnO₂ nanofibers with Ω‐shaped ZnO shell (SnO₂@ZnO) is fabricated. With 87.4% transmittance at 550 nm, SnO₂@ZnO PD exhibits a high photo‐to‐dark current ratio up to 10⁴ at around 280 nm. Owing to the additional Ω‐shaped ZnO shell, SnO₂@ZnO PD possesses a responsivity of nearly 100 A W^?1 under 5 V bias and the illumination of 250 nm light, which is 30‐time enhancement of pristine SnO₂ PD. The enhancement is mainly attributed to type‐II energy band structure. Furthermore, by changing the direction of incident light, SnO₂@ZnO PD has a high UV selectivity with an UV–vis rejection ratio (R _{250 nm}/R _{400 nm}) as much as 2.0 × 10³ at 5 V bias under back illumination, which is fourfold higher than that under face illumination. The UV selectivity improvement may be attributed to light confinement in the Ω‐shaped structure. With both theoretical simulations and experimental comparisons, it is demonstrated that the unique compact Ω‐shaped nanostructure does contribute to photon trapping and gaining process, especially in back‐illumination configuration. The approach can be easily extended to other materials, preparing novel building blocks for optoelectronic devices.     

Carbonyl‐β‐Cyclodextrin as a Novel Binder for Sulfur Composite Cathodes in Rechargeable Lithium Batteries

As one of the essential components in electrodes, the binder affects the performance of a rechargeable battery. By modifying β‐cyclodextrin (β‐CD), an appropriate binder for sulfur composite cathodes is identified. Through a partial oxidation reaction in H₂O₂ solution, β‐CD is successfully modified to carbonyl‐β‐cyclodextrin (C‐β‐CD), which exhibits a water solubility ca. 100 times that of β‐CD at room temperature. C‐β‐CD possesses the typical properties of an aqueous binder: strong bonding strength, high solubility in water, moderate viscosity, and wide electrochemical windows. Sulfur composite cathodes with C‐β‐CD as the binder demonstrate a high reversible capacity of 694.2 mA h g_(composite)^?1 and 1542.7 mA h g_(sulfur)^?1, with a sulfur utilization approaching 92.2%. The discharge capacity remains at 1456 mA h g_(sulfur)^?1 after 50 cycles, which is much higher than that of the cathode with unmodified β‐CD as binder. Combined with its low cost and environmental benignity, C‐β‐CD is a promising binder for sulfur cathodes in rechargeable lithium batteries with high electrochemical performance.     

Non‐Lithographic Fabrication of All‐2D α‐MoTe2 Dual Gate Transistors

As one of the emerging new transition‐metal dichalcogenides materials, molybdenum ditelluride (α‐MoTe₂) is attracting much attention due to its optical and electrical properties. This study fabricates all‐2D MoTe₂‐based field effect transistors (FETs) on glass, using thin hexagonal boron nitride and thin graphene in consideration of good dielectric/channel interface and source/drain contacts, respectively. Distinguished from previous works, in this study, all 2D FETs with α‐MoTe₂ nanoflakes are dual‐gated for driving higher current. Moreover, for the present 2D dual gate FET fabrications on glass, all thermal annealing and lithography processes are intentionally exempted for fully non‐lithographic method using only van der Waal's forces. The dual‐gate MoTe₂ FET displays quite a high hole and electron mobility over ≈20 cm² V^?1 s^?1 along with ON/OFF ratio of ≈10⁵ in maximum as an ambipolar FET and also demonstrates high drain current of a few tens‐to‐hundred μA at a low operation voltage. It appears promising enough to drive organic light emitting diode pixels and NOR logic functions on glass.     

Functional and Well‐Defined β‐Sheet‐Assembled Porous Spherical Shells by Surface‐Guided Peptide Formation

Polypeptides have attracted widespread attention as building blocks for complex materials due to their ability to form higher‐ordered structures such as β‐sheets. However, the ability to precisely control the formation of well‐defined β‐sheet‐assembled materials remains challenging as β‐sheet formation tends to lead to ill‐defined and unprocessable aggregates. This work reports a simple, rapid, and robust strategy to form well‐defined peptide β‐sheet‐assembled shells (i.e., hollow spheres) by employing surface‐initiated N‐carboxyanhydride ring‐opening polymerization under a highly efficient surface‐driven approach. The concept is demonstrated by the preparation of enzyme‐degradable rigid shell architectures composed of H‐bonded poly(L‐valine) (PVal) grafts with porous and sponge‐like surface morphology. The porous PVal‐shells exhibit a remarkable and unprecedented ability to non‐covalently entrap metal nanoparticles, proteins, drug molecules, and biorelevant polymers, which could potentially lead to a diverse range of biodegradable and functional platforms for applications ranging from therapeutic delivery to organic catalysis.     

Long‐Circulating Drug‐Dye‐Based Micelles with Ultrahigh pH‐Sensitivity for Deep Tumor Penetration and Superior Chemo‐Photothermal Therapy

Nanocarriers for chemo‐photothermal therapy suffer from insufficient retention at the tumor site and poor penetration into tumor parenchyma. A smart drug‐dye‐based micelle is designed by making the best of the structural features of small‐molecule drugs. P‐DOX is synthesized by conjugating doxorubicin (DOX) with poly(4‐formylphenyl methacrylate‐co‐2‐(diethylamino) ethyl methacrylate)‐b‐polyoligoethyleneglycol methacrylate (P(FPMA‐co‐DEA)‐b‐POEGMA) via imine linkage. Through the π–π stacking interaction, IR780, a near‐infrared fluorescence dye as well as a photothermal agent, is integrated into the micelles (IR780‐PDMs) with the P‐DOX. The IR780‐PDMs show remarkably long blood circulation (t_1/2β = 22.6 h). As a result, a progressive tumor accumulation and retention are presented, which is significant to the sequential drug release. Moreover, when entering into a moderate acidic tumor microenvironment, IR780‐PDMs can dissociate into small‐size conjugates and IR780, which obviously increases the penetration depth of drugs, and then improves the lethality to deep‐seated tumor cells. Owing to the high delivery efficiency and superior chemo‐photothermal therapeutic efficacy of IR780‐PDMs, 97.6% tumor growth in the A549 tumor‐bearing mice is suppressed with a low dose of intravenous injection (DOX, 1.5 mg kg^?1; IR780, 0.8 mg kg^?1). This work presents a brand‐new strategy for long‐acting intensive cancer therapy.     

Controlled Polarizability of One‐Nanometer‐Thick Oxide Nanosheets for Tailored,High‐κ Nanodielectrics

An important challenge in current microelectronics research is the development of techniques for making smaller, higher‐performance electronic components. In this context, the fabrication and integration of ultrathin high‐κ dielectrics with good insulating properties is an important issue. Here, we report on a rational approach to produce high‐performance nanodielectrics using one‐nanometer‐thick oxide nanosheets as a building block. In titano niobate nanosheets (TiNbO₅, Ti₂NbO₇, Ti₅NbO₁₄), the octahedral distortion inherent to site‐engineering by Nb incorporation results in a giant molecular polarizability, and their multilayer nanofilms exhibit a high dielectric constant (160–320), the largest value seen so far in high‐κ nanofilms with thickness down to 10 nm. Furthermore, these superior high‐κ properties are fairly temperature‐independent with low leakage‐current density (<10^?7 A cm^?2). This work may provide a new recipe for designing nanodielectrics desirable for practical high‐κ devices.     

Mg3+δSbxBi2−x Family: A Promising Substitute for the State‐of‐the‐Art n‐Type Thermoelectric Materials near Room Temperature

The Bi₂Te_3?xSe_x family has constituted n‐type state‐of‐the‐art thermoelectric materials near room temperature (RT) for more than half a century, which dominates the active cooling and novel heat harvesting application near RT. However, the drawbacks of a brittle nature and Te‐content restricts the possibility for exploring potential applications. Here, it is shown that the Mg_3+δSb_xBi_2?x family ((ZT)_avg = 1.05) could be a promising substitute for the Bi₂Te_3?xSe_x family ((ZT)_avg = 0.9–1.0) in the temperature range of 50–250 °C based on the comparable thermoelectric performance through a synergistic effect from the tunable bandgap using the alloy effect and the suppressible Mg‐vacancy formation using an interstitial Mn dopant. The former is to shift the optimal thermoelectric performance to near RT, and the latter is helpful to partially decouple the electrical transport and thermal transport in order to get an optimal RT power factor. The positive temperature dependence of the bandgap suggests this family is also a superior medium‐temperature thermoelectric material for the significantly suppressed bipolar effect. Furthermore, a two times higher mechanical toughness, compared with the Bi₂Te_3?xSe_x family, allows for a promising substitute for state‐of‐the‐art n‐type thermoelectric materials near RT.     

A Novel Room‐Temperature Multiferroic System of Hexagonal Lu1−xInxFeO3

In the present work, h‐RFeO₃ multiferroic ceramics are designed and created by introducing chemical pressure (In‐substitution for Lu) in LuFeO₃. Lu_1?xIn_xFeO₃ (x = 0‐0.75) ceramics are prepared by the standard solid‐state reaction process. The crystal structure of the present ceramics is tuned from centrosymmetric Pbnm (x = 0) to non‐centrosymmetric P6₃cm (x = 0.4–0.6), and subsequently to centrosymmetric P6₃/mmc (x = 0.75), while the Pbnm and P6₃cm biphase structure is detected for x = 0.25. The Curie temperature for the polar P6₃cm (x = 0.4–0.6) phase decreases from >1000 to ≈550 K with increasing x. Cloverleaf ferroelectric domain structures are determined in polar Lu_0.5In_0.5FeO₃ samples, and the ferroelectric domain walls at atomic scale are evaluated by the aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy (HAADF STEM), where the spontaneous polarization of 1.73 µC cm^?2 is determined for x = 0.5. The spontaneous polarization is also confirmed by calculating the site displacement from the centrosymmetric phase based on the X‐ray diffraction (XRD) data. Meanwhile, two magnetic transitions are determined for all compositions, that is, paramagnetic to antiferromagnetic transition at Néel temperature T_N (≈350 K for x = 0.4–0.6), and antiferromagnetic to weak‐ferromagnetic transition at spin‐reorientation temperature T_SR. The co‐presence of ferroelectric and antiferromagnetic orders confirms the present ceramics as promising room‐temperature multiferroic materials.     

Quantification of Grafting Densities Achieved via Modular “Grafting‐to” Approaches onto Divinylbenzene Microspheres

The surface modification of divinylbenzene (DVB)‐based microspheres is performed via a combination of reversible addition fragmentation chain transfer (RAFT) polymerization and rapid hetero‐Diels–Alder (HDA) chemistry with the aim of quantifying the grafting densities achieved using this “grafting‐to” method. Two variants of the RAFT‐HDA concept are employed to achieve the functionalization of the microspheres. In the first approach, the microspheres are functionalized with a highly reactive diene, i.e., cyclopentadiene, and are subsequently reacted with polystyrene chains (number‐averaged molecular weight, M_n = 4200 g mol^?1; polydispersity index, PDI = 1.12.) that carry a thiocarbonyl moiety functioning as a dienophile. The functionalization of the microspheres is achieved rapidly under ambient conditions, without the aid of an external catalyst. The surface grafting densities obtained are close to 1.2 × 10²⁰ chains per gram of microspheres. In the second approach, the functionalization proceeds via the double bonds inherently available on the microspheres, which are reacted with poly(isobornyl acrylate) chains carrying a highly dienophilic thiocarbonyl functionality; two molecular weights (M_n = 6000 g mol^?1, PDI = 1.25; M_n = 26 000 g mol^?1, PDI = 1.26) are used. Due to the less reactive nature of the dienes in the second approach, functionalization is carried out at elevated temperatures (T = 60 °C) yet in the absence of a catalyst. In this case the surface grafting density is close to 7 chains nm^?2 for M_n = 6000 g mol^?1 and 4 chains nm^?2 for M_n = 26 000 g mol^?1, or 2.82 × 10¹⁹ and 1.38 × 10¹⁹ chains g^?1, respectively. The characterization of the microspheres at various functionalization stages is performed via elemental analysis for the quantification of the grafting densities and attenuated total reflectance (ATR) IR spectroscopy as well as confocal microscopy for the analysis of the surface chemistry.     

Versatile α,ω‐Disubstituted Tetrathienoacene Semiconductors for High Performance Organic Thin‐Film Transistors

Facile one‐pot [1 + 1 + 2] and [2 + 1 + 1] syntheses of thieno[3,2‐b]thieno[2′,3′:4,5]thieno[2,3‐d]thiophene (tetrathienoacene; TTA) semiconductors are described which enable the efficient realization of a new TTA‐based series for organic thin‐film transistors (OTFTs). For the perfluorophenyl end‐functionalized derivative DFP‐TTA , the molecular structure is determined by single‐crystal X‐ray diffraction. This material exhibits n‐channel transport with a mobility as high as 0.30 cm²V^?1s^?1 and a high on‐off ratio of 1.8 × 10⁷. Thus, DFP‐TTA has one of the highest electron mobilities of any fused thiophene semiconductor yet discovered. For the phenyl‐substituted analogue, DP‐TTA , p‐channel transport is observed with a mobility as high as 0.21 cm²V^?1s^?1. For the 2‐benzothiazolyl (BS‐) containing derivative, DBS‐TTA , p‐channel transport is still exhibited with a hole mobility close to 2 × 10^?3 cm²V^?1s^?1. Within this family, carrier mobility magnitudes are strongly dependent on the semiconductor growth conditions and the gate dielectric surface treatment.     

Outage probability bound of decode and forward two‐way full‐duplex relay employing spatial modulation over cascaded α − μ channels

The system performance of mobile‐to‐mobile (D2D) cooperative communication has been improved by utilizing spatial modulation (SM) in this paper. The proposed system employs decode and forward (DF) relaying technique along with physical layer network coding (PLNC); hence, it has been named as SM‐based decode and forward two‐way relay (DFTWR). It enables full‐duplex communication thereby enhancing the system efficiency. Information bits are exchanged between the two bidirectional nodes. For two bits of information exchange, the antenna index is conveyed by the least significant bit (LSB) of the data symbol while the most significant bit (MSB) carries the message. The system performance has been investigated by analyzing certain performance metrics like lower and upper bounds of outage probability and average data rate for N‐α‐μ cascaded fading channels. The change in the system performance by varying certain parameters like relative geometrical gain, fading coefficients, and number of cascaded components has also been put forth in this paper.     

Red Phosphorescent Iridium Complex Containing Carbazole‐Functionalized β‐Diketonate for Highly Efficient Nondoped Organic Light‐Emitting Diodes

A novel red phosphorescent iridium complex containing a carbazole‐functionalized β‐diketonate, Ir(DBQ)₂(CBDK) (bis(dibenzo[f,h]quinoxalinato‐N,C²) iridium (1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate)) is designed, synthesized, and characterized. The electrophosphorescence properties of a nondoped device using the title complex as an emitter with a device configuration of indium tin oxide (ITO)/N,N′‐diphenyl‐N,N′‐bis(1‐naphthyl)‐1,1′‐diphenyl‐4,4′‐diamine (NPB; 20 nm)/iridium complex (20 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 5 nm)/tris(8‐hydroxyquinoline) (AlQ; 30 nm)/Mg_0.9Ag_0.1 (200 nm)/Ag (80 nm) are examined. The results show that the nondoped device achieves a maximum lumen efficiency as high as 3.49 lm W^–1. To understand this excellent result observed, two reference complexes Ir(DBQ)₂(acac), where acac is the acetyl acetonate anion, and Ir(DBQ)₂(FBDK), [bis(dibenzo[f,h]quinoxalinato‐N,C²) iridium (1‐(9‐methyl‐fluoren‐9‐yl)‐6,6‐dimethylheptane‐3,5‐diketonate)], have also been synthesized, and as emitters they were examined under the same device configuration. The maximum lumen efficiency of the former compound is found to be 0.26 lm W^–1 while that for the latter is 0.37 lm W^–1, suggesting that the excellent performance of Ir(DBQ)₂(CBDK) can be attributed mainly to an improved hole‐transporting property that benefits the exciton transport. In addition, a bulky diketonate group separates the emitter centers from each other, which is also important for organic light‐emitting diodes.     

Enhancing Ultralong Organic Phosphorescence by Effective π‐Type Halogen Bonding

Efficient ultralong organic phosphorescent materials have potential applications in some fields, such as bioimaging, anti‐counterfeiting, and sensors. Nevertheless, phosphorescence efficiencies of metal‐free organic materials are low due to weak spin–orbit coupling and vigorous nonradiative transitions under ambient conditions. Here a chemical strategy to improve phosphorescence efficiency with intermolecular π‐type halogen bonding construction via isomerism is presented. X‐ray single crystal analysis reveals that different halogen bonding is formed among p‐BrTCz, m‐BrTCz, and o‐BrTCz crystals. Phosphorescence efficiency of m‐BrTCz in solid can reach 13.0%, seven times of o‐BrTCz in solid owing to effective π‐type halogen bonding, which is further confirmed by theoretical calculations. However, ultralong phosphorescence lifetimes are little affected, 155, 120, and 156 ms for p‐BrTCz, m‐BrTCz, and o‐BrTCz in the solid state, respectively. Furthermore, a simple pattern for data encryption and decryption is first demonstrated under sunlight. This result will provide an approach for improving the phosphorescent efficiency of metal‐free organic phosphors with ultralong luminescence.