Improved Design of Slope-Shaped Hole-Blocking Layer and Electron-Blocking Layer in AlGaN-Based Near-Ultraviolet Laser Diodes.

The injection and leakage of charge carriers have a significant impact on the optoelectronic performance of GaN-based lasers. In order to improve the limitation of the laser on charge carriers, a slope-shape hole-barrier layer (HBL) and electron-barrier layer (EBL) structure are proposed for near-UV (NUV) GaN-based lasers. We used Crosslight LASTIP for the simulation and theoretical analysis of the energy bands of HBL and EBL. Our simulations suggest that the energy bands of slope-shape HBL and EBL structures are modulated, which could effectively suppress carrier leakage, improve carrier injection efficiency, increase stimulated radiation recombination rate in quantum wells, reduce the threshold current, improve optical field distribution, and, ultimately, improve laser output power. Therefore, using slope-shape HBL and EBL structures can achieve the superior electrical and optical performance of lasers.

The CuSCN layer between BiVO4 and NiFeOx for facilitating photogenerated carrier transfer and water oxidation kinetics.

Modification of oxygen evolution co-catalyst (OEC) on the surface of bismuth vanadate (BiVO4) can effectively improve the kinetics of water oxidation, but it is still limited by the small hole extraction driving force at the BiVO4/OEC interface. Modulating the BiVO4/OEC interface with a hole transfer layer (HTL) is expected to facilitate hole transport from BiVO4 to the OEC surface. Herein, a copper(I) thiocyanate (CuSCN) HTL is inserted between BiVO4 and NiFeOx OEC to create BiVO4/CuSCN/NiFeOx photoanode, resulting in a significant enhancement of photoelectrochemical (PEC) water splitting performance. From electrochemical analyses and density functional theory (DFT) simulations, the markedly enhanced PEC performance is attributed to the insertion of CuSCN as an HTL, which promotes the extraction of holes from BiVO4 surface and boosts the water oxidation kinetics. The optimal photoanode achieves a photocurrent density of 5.6 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (vs. RHE) and an impressive charge separation efficiency of 96.2 %. This work offers valuable insights into the development of advanced photoanodes for solar energy conversion and emphasizes the importance of selecting an appropriate HTL to mitigate recombination at the BiVO4/OEC interface.

SiC@NiO Core-Shell Nanowire Networks-Based Optoelectronic Synapses for Neuromorphic Computing and Visual Systems at High Temperature.

1D nanowire networks, sharing similarities of structure, information transfer, and computation with biological neural networks, have emerged as a promising platform for neuromorphic systems. Based on brain-like structures of 1D nanowire networks, neuromorphic synaptic devices can overcome the von Neumann bottleneck, achieving intelligent high-efficient sensing and computing function with high information processing rates and low power consumption. Here, high-temperature neuromorphic synaptic devices based on SiC@NiO core-shell nanowire networks optoelectronic memristors (NNOMs) are developed. Experimental results demonstrate that NNOMs attain synaptic short/long-term plasticity and modulation plasticity under both electrical and optical stimulation, and exhibit advanced functions such as short/long-term memory and "learning-forgetting-relearning" under optical stimulation at both room temperature and 200 °C. Based on the advanced functions under light stimulus, the constructed 5 × 3 optoelectronic synaptic array devices exhibit a stable visual memory function up to 200 °C, which can be utilized to develop artificial visual systems. Additionally, when exposed to multiple electronic or optical stimuli, the NNOMs effectively replicate the principles of Pavlovian classical conditioning, achieving visual heterologous synaptic functionality and refining neural networks. Overall, with abundant synaptic characteristics and high-temperature thermal stability, these neuromorphic synaptic devices offer a promising route for advancing neuromorphic computing and visual systems.

Revelation of adhesive proteins affecting cellular contractility through reference-free traction force microscopy.

Over the past few decades, the critical role played by cellular contractility associated mechanotransduction in the regulation of cell functions has been revealed. In this case, numerous biomaterials have been chemically or structurally designed to manipulate cell behaviors through the regulation of cellular contractility. In particular, adhesive proteins including fibronectin, poly-L-lysine and collagen type I have been widely applied in various biomaterials to improve cell adhesion. Therefore, clarifying the effects of adhesive proteins on cellular contractility has been valuable for the development of biomaterial design. In this study, reference-free traction force microscopy with a well-organized microdot array was designed and prepared to investigate the relationship between adhesive proteins, cellular contractility, and mechanotransduction. The results showed that fibronectin and collagen type I were able to promote the assembly of focal adhesions and further enhance cellular contraction and YAP activity. In contrast, although poly-L-lysine supported cell spreading and elongation, it was inefficient at inducing cell contractility and activating YAP. Additionally, compared with cellular morphogenesis, cellular contraction was essential for YAP activation.

Copious Dislocations Defect in Amorphous/Crystalline/Amorphous Sandwiched Structure P-NiMoO4 Electrocatalyst toward Enhanced Hydrogen Evolution Reaction.

The design and synthesis of efficient, inexpensive, and long-term stable heterostructured electrocatalysts with high-density dislocations for hydrogen evolution reaction in alkaline media and seawater are still a great challenge. An amorphous/crystalline/amorphous sandwiched structure with abundant dislocations were synthesized through thermal phosphidation strategies. The dislocations play an important role in the hydrogen evolution reactions. Copious dislocation defects, combined with cracks, and the synergistic interfacial effect between crystalline phase and amorphous phase regulate the electronic structure of electrocatalyst, provide more active sites, and thus endow the electrocatalysts with excellent catalytic activity under alkaline water and seawater. The overpotentials of P-NiMoO4 at 10 mA/cm2 in 1 M KOH aqueous solution and seawater are 45 and 75 mV, respectively. Additionally, the P-NiMoO4 electrocatalyst exhibits long-term stability over 100 h. This study provides a simple approach for synthesizing amorphous/crystalline/amorphous sandwiched non-noble-metal electrocatalysts with abundant dislocations for hydrogen evolution reaction.

Artificial Optoelectronic Synapse Based on Violet Phosphorus Microfiber Arrays.

Memristor-based artificial synapses are regarded as the most promising candidate to develop brain-like neuromorphic network computers and overcome the bottleneck of Von-Neumann architecture. Violet phosphorus (VP) as a new allotrope of available phosphorus with outstanding electro-optical properties and stability has attracted more and more attention in the past several years. In this study, large-scale, high-yield VP microfiber vertical arrays have been successfully developed on a Sn-coated graphite paper and are used as the memristor functional layers to build reliable, low-power artificial synaptic devices. The VP devices can well mimic the major synaptic functions such as short-term memory (STM), long-term memory (LTM), paired-pulse facilitation (PPF), spike timing-dependent plasticity (STDP), and spike rate-dependent plasticity (SRDP) under both electrical and light stimulation conditions, even the dendritic synapse functions and simple logical operations. By virtue of the excellent performance, the VP artificial synapse devices can be conductive to building high-performance optic-neural synaptic devices simulating the human-like optic nerve system. On this basis, Pavlov's associative memory can be successfully implemented optically. This study provides a promising approach for the design and manufacture of VP-based artificial synaptic devices and outlines a direction with multifunctional neural devices.

Porous N-Doped Carbon Decorated with Atomically Dispersed Independent Dual Metal Sites from Energetic Zeolite Imidazolate Frameworks as Bidirectional Catalysts for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have ultrahigh theoretical specific capacity and energy density, which are considered to be very promising energy storage devices. However, the slow redox kinetics of polysulfides are the main reason for the rapid capacity decay of Li-S batteries. A reasonable electrocatalyst for the Li-S battery should reduce the reaction barrier and accelerate the reaction kinetics of the bidirectional catalytic conversion of lithium polysulfides (LiPSs), thereby reducing the cumulative concentration of LiPSs in the electrolyte. In this report, porous N-doped carbon nanofibers decorated with independent dual metal sites as catalysts for Li-S batteries were fabricated in one step using a fusion-foaming method. Experimental and theoretical analyses demonstrate that the synergistic effect of independent dual metal sites provides strong LiPS affinity, improved electronic conductivity, and enhanced redox kinetics of polysulfides. Therefore, the assembled Li-S battery exhibits high rate performance (discharge specific capacity of 771 mA h g-1 at 2C) and excellent cycle stability (capacity decay rate of 0.51% after 1000 cycles at 1C).

Effects of Thermal-Strain-Induced Atomic Intermixing on the Interfacial and Photoluminescence Properties of InGaAs/AlGaAs Multiple Quantum Wells.

Quantum-well intermixing (QWI) technology is commonly considered as an effective methodology to tune the post-growth bandgap energy of semiconductor composites for electronic applications in diode lasers and photonic integrated devices. However, the specific influencing mechanism of the interfacial strain introduced by the dielectric-layer-modulated multiple quantum well (MQW) structures on the photoluminescence (PL) property and interfacial quality still remains unclear. Therefore, in the present study, different thicknesses of SiO2-layer samples were coated and then annealed under high temperature to introduce interfacial strain and enhance atomic interdiffusion at the barrier-well interfaces. Based on the optical and microstructural experimental test results, it was found that the SiO2 capping thickness played a positive role in driving the blueshift of the PL peak, leading to a widely tunable PL emission for post-growth MQWs. After annealing, the blueshift in the InGaAs/AlGaAs MQW structures was found to increase with increased thickness of the SiO2 layer, and the largest blueshift of 30 eV was obtained in the sample covered with a 600 nm thick SiO2 layer that was annealed at 850 °C for 180 s. Additionally, significant well-width fluctuations were observed at the MQW interface after intermixing, due to the interfacial strain introduced by the thermal mismatch between SiO2 and GaAs, which enhanced the inhomogeneous diffusion rate of interfacial atoms. Thus, it can be demonstrated that the introduction of appropriate interfacial strain in the QWI process is of great significance for the regulation of MQW band structure as well as the control of interfacial quality.

Electronic Asymmetry Engineering of Fe-N-C Electrocatalyst via Adjacent Carbon Vacancy for Boosting Oxygen Reduction Reaction.

Single-atomic transition metal-nitrogen-carbon (M-N-C) structures are promising alternatives toward noble-metal-based catalysts for oxygen reduction reaction (ORR) catalysis involved in sustainable energy devices. The symmetrical electronic density distribution of the M─N4 moieties, however, leads to unfavorable intermediate adsorption and sluggish kinetics. Herein, a Fe-N-C catalyst with electronic asymmetry induced by one nearest carbon vacancy adjacent to Fe─N4 is conceptually produced, which induces an optimized d-band center, lowered free energy barrier, and thus superior ORR activity with a half-wave potential (E1/2 ) of 0.934 V in a challenging acidic solution and 0.901 V in an alkaline solution. When assembled as the cathode of a Zinc-air battery (ZAB), a peak power density of 218 mW cm-2 and long-term durability up to 200 h are recorded, 1.5 times higher than the noble metal-based Pt/C+RuO2 catalyst. This work provides a new strategy on developing efficient M-N-C catalysts and offers an opportunity for the real-world application of fuel cells and metal-air batteries.

Three-dimensional carbon network-supported black phosphorus-cobalt heterojunctions: An efficient electrocatalyst for high-rate oxygen evolution.

Black phosphorus (BP), as a burgeoning two-dimensional material, has shown good electrocatalytic activity due to its unique electronic structure and abundant active sites.However, the presence of lone pair electrons in black phosphorus leads to its poor stability and rapid degradation in an oxygen/water environment, which greatly limits its practical application. Herein, BP-Co heterojunctions were synthesized on carbon nanotube@nitrogen-doped carbon (BP-Co/CNT@NC) by the pyrolysis of ZnCo-zeolitic imidazolate frameworks and subsequent solvothermal treatment. The BP-Co Schottky junction improved the electrocatalytic stability of BP, modulated its electronic structure, improved its conductivity and electron transfer during the electrocatalytic reaction. Density functional theory calculation was used to confirm the electron transfer and redistribution at the interface between BP and Co, which constructed an oppositely charged region and formed a strong built-in field. Energy band configuration analysis revealed a narrowed band gap because of the formation of BP-Co Schottky junction. Consequently, the optimized BP-Co/CNT@NC exhibited a superior oxygen evolution reaction (OER) performance, a low overpotential of 370 mV@100 mA/cm2, with a small Tafel slope of 40 mV/dec and good long-term stability. Particularly, the catalyst has an excellent OER performance at the high current density of 100-400 mA/cm2. This strategy improves the stability of BP electrocatalysts and strengthens their utilization in electrocatalytic applications.

Stabilizing Solid-state Lithium Metal Batteries through In Situ Generated Janus-heterarchical LiF-rich SEI in Ionic Liquid Confined 3D MOF/Polymer Membranes.

Pursuing high power density lithium metal battery with high safety is essential for developing next-generation energy-storage devices, but uncontrollable electrolyte degradation and the consequence formed unstable solid-electrolyte interface (SEI) make the task really challenging. Herein, an ionic liquid (IL) confined MOF/Polymer 3D-porous membrane was constructed for boosting in situ electrochemical transformations of Janus-heterarchical LiF/Li3 N-rich SEI films on the nanofibers. Such a 3D-Janus SEI-incorporated into the separator offers fast Li+ transport routes, showing superior room-temperature ionic conductivity of 8.17×10-4  S cm-1 and Li+ transfer number of 0.82. The cryo-TEM was employed to visually monitor the in situ formed LiF and Li3 N nanocrystals in SEI and the deposition of Li dendrites, which is greatly benefit to the theoretical simulation and kinetic analysis of the structural evolution during the battery charge and discharge process. In particular, this membrane with high thermal stability and mechanical strength used in solid-state Li||LiFePO4 and Li||NCM-811 full cells and even in pouch cells showed enhanced rate-performance and ultra-long life spans.

Atomic-scale insights into the interfacial charge transfer in a NiO/CeO2 heterostructure for electrocatalytic hydrogen evolution.

To understand the underlying mechanism of the interfacial charge transfer and local chemical state variation in the nonprecious-based hydrogen evolution reaction (HER) electrocatalysts, a model system of the NiO/CeO2 heterostructure was chosen for investigation using a combination of the advanced electron microscopic characterization and first-principles calculations. The results directly proved that interfacial charge transfer occurs from Ni to Ce, leading to reduction in the valence state of Ce and increased formation of VO. This would optimize ΔGH* and facilitate the hydrogen evolution process, resulting in outstanding HER performance in 1 M KOH with a low overpotential of 99 mV at the current density of 10 mA•cm-2 and a modest Tafel slope of 78.4 mV•dec-1 for the NiO/CeO2 heterostructure sample. Therefore, the improved HER performance could be attributed to the synergistic coupling interactions and electron redistribution at the interface of NiO and CeO2. These results concretely demonstrate the direct determination of the interfacial structure of the heterostructure and provide atomistic insights to unravel the underlying mechanism of interfacial charge transfer induced HER performance improvement.

One-Step Synthesis of White-Light-Emitting Carbon Dots for White LEDs with a High Color Rendering Index of 97.

White-light-emitting carbon dots (WCDs) show innate advantages as phosphors in white light-emitting diodes (WLEDs). For WLEDs, the color rendering index (CRI) is the most important metric to evaluate its performance. Herein, WCDs are prepared by a facile one-step solvothermal reaction of trimellitic acid and o-phenylenediamine. It consists of four CDs identified by column chromatography as blue, green, yellow, red, and thus white light is a superposition of these four types of light. The mixture of the four CDs undergoes Förster resonance energy transfer to induce the generation of white light. The photoluminescence of WCDs originates from the synergistic effect of carbon core and surface states. Thereinto, the carbon core states dominate in RCDs, and the increase of amide contents and degree of conjugation promote the redshift of the emission spectra, which is further confirmed by theoretical calculations. In addition, a high CRI of 97 is achieved when the WCDs are used as phosphors to fabricate WLEDs, which is almost the highest value up to now. The multicolor LEDs can also be fabricated by using the four multicolor CDs as phosphors, respectively. This work provides a novel approach to explore the rapid preparation of low-cost, high-performance WCDs and CDs-based WLEDs.

A Dual-Wavelength Phosphorescent Anti-Counterfeiting Copolymer Containing Eu(III) and Tb(III).

The anti-counterfeiting technology of banknotes, bills and negotiable securities is constantly copied, and it is urgent to upgrade its anti-counterfeiting technology. In view of the defect of easy replication of single-wavelength anti-counterfeiting technology, the bonded copolymer PMEuTb was synthesized, employing the technique of first coordination and then polymerization. The molecular structure of copolymer PMEuTb was confirmed by infrared spectrum and UV-vis absorption spectrum. The internal mechanism of negative correlation between initiator concentration and number-average molecular weight Mn of the copolymer was revealed, and the positive correlation between Mn and luminescent behavior of the copolymer was analyzed. The luminescent properties of copolymer PMEuTb with initiator amount of 0.1% were investigated, the copolymer PMEuTb exhibits dual-wavelength emission of green light and red light under the excitation of ultraviolet light at 254 nm and 365 nm. The copolymer has the lifetime of 1.083 ms at 5D4-7F5 transition and 0.665 ms at 5D0-7F2 transition, which belongs to phosphorescent emitting materials. The copolymer remains stable at 240 °C, and variable temperature photoluminescent spectra demonstrate the luminescent intensity remains 85% at 333 K, meeting the requirements of room temperature phosphorescent anti-counterfeiting materials. The luminescent patterns made by standard screen printing display the green and cuticolor logo at 254 nm and 365 nm, respectively, indicating that the bonded phosphors PMEuTb has potential application in phosphorescent anti-counterfeiting.

Covalent Bonding Enhanced Polypropylene Based T-ZIF-8 Masterbatch with Superior Photocatalytic and Antibacterial Performances.

In order to solve the problem of poor compatibility between modified-ZIF-8 nanoparticles and mask matrix polypropylene (PP) and melt-blown materials, in this work, PP based modified-ZIF-8 antibacterial masterbatch was prepared employing surface modification and torque blending method. IR, SEM, XRD, XPS, DSC results confirm that the antibacterial masterbatch maintains the chemical and crystal structure of modified-ZIF-8 and the thermal stability of PP. Photocatalytic performance indicates that the antibacterial masterbatch basically maintains the photoresponse range of modified-ZIF-8, has narrower band gap and the superior photocatalytic performance than that of modified-ZIF-8. The photocatalytic antibacterial mechanism of ·O2- and h+ as antibacterial active species is revealed according to the energy band structure and free radical capture experiment. The photocatalytic antibacterial activity of the antibacterial masterbatch against Staphylococcus aureus and Escherichia coli under different dosage holds that the relationship between antibacterial rate and antibacterial agent concentration conforms to Beta distribution, demonstrating second-order kinetic behavior. The antibacterial properties reach the maximum when the loading of modified-ZIF-8 is 2% of the total weight of PP and melt-blown materials. S. aureus and E. coli could be completely killed when the simulated sunlight is irradiated for 30 min. These results indicate that PP based modified-ZIF-8 antibacterial masterbatch has potential application in photocatalytic antibacterial masks.

In Situ Growth of Iron Sulfide on Fast Charge Transfer V2 C-MXene for Superior Sodium Storage Anodes.

Due to the upstream pressure of lithium resources, low-cost sodium-ion batteries (SIBs) have become the most potential candidates for energy storage systems in the new era. However, anode materials of SIBs have always been a major problem in their development. To address this, V2 C/Fe7 S8 @C composites with hierarchical structures prepared via an in situ synthesis method are proposed here. The 2D V2 C-MXene as the growth substrate for Fe7 S8  greatly improves the rate capability of SIBs, and the carbon layer on the surface provides a guarantee for charge-discharge stability. Unexpectedly, the V2 C/Fe7 S8 @C anode achieves satisfactory sodium storage capacity and exceptional rate performance (389.7 mAh g-1  at 5 A g-1 ). The sodium storage mechanism and origin of composites are thoroughly studied via ex situ characterization techniques and first-principles calculations. Furthermore, the constructed sodium-ion capacitor assembled with N-doped porous carbon delivers excellent energy density (135 Wh kg-1 ) and power density (11 kW kg-1 ), showing certain practical value. This work provides an advanced system of sodium storage anode materials and broadens the possibility of MXene-based materials in the energy storage.

Sulfur-deficient MoS2-carbon hollow nanospheres for synergistic trapping and electrocatalytic conversion of polysulfides.

Lithium-sulfur battery is one of the most promising candidates for next-generation energy storage systems, but the serious shuttle effect and sluggish reaction kinetics of polysulfides impair its practical applications. Herein, sulfur-deficient MoS2/carbon hollow nanospheres (MoS2-CHNs) are firstly synthesized by a NaCl-template pyrolysis and employed as sulfur host for lithium-sulfur batteries. TEM analysis reveals that carbon hollow nanospheres existing in the composite are the backbones that help to immobilize the ultrathin MoS2 nanosheets and ensure their large specific surface area. The MoS2 nanosheets consist of 5-10 layers of MoS2 with rich sulfur vacancies. The first principle calculation demonstrates that sulfur vacancy led to an intensively enhanced binding energy (-4.70 eV) towards Li2S6 compared to the pristine MoS2 (-1.57 eV). It suppressed the shuttle effect efficiently. The catalytic experiments reveal that MoS2-CHNs have a superior ability for the nucleation of Li2S and bidirectional electrocatalytic capability for the conversion of polysulfide. The large storage space inside MoS2-CHNs can work as a reservoir for intermediate polysulfides to substantially reduce the concentration overpotential. Due to this advantageous structural design of MoS2-CHNs electrode, its reversible capacity remains 1139 mAh g-1 after 100 cycles at 0.2C, and 600 mAh g-1 after 500 cycles at 5C with a sulfur loading of 5 mg cm-2. Even though the sulfur loading increases to 10 mg cm-2, the Li-S battery delivers a stable capacity of 978 mAh g-1 after 50 cycles at 0.2C. So the MoS2-CHNs demonstrate a promising application for high-energy Li-S batteries.

Synthesis of Fibrous Phosphorus Micropillar Arrays with Pyro-Phototronic Effects.

The bottom-up preparation of two-dimensional material micro-nano structures at scale facilitates the realisation of integrated applications in optoelectronic devices. Fibrous Phosphorus (FP), an allotrope of black phosphorus (BP), is one of the most promising candidate materials in the field of optoelectronics with its unique crystal structure and properties.[1] However, to date, there are no bottom-up micro-nano structure preparation methods for crystalline phosphorus allotropes.[1c, 2] Herein, we present the bottom-up preparation of fibrous phosphorus micropillar (FP-MP) arrays via a low-pressure gas-phase transport (LP-CVT) method that controls the directional phase transition from amorphous red phosphorus (ARP) to FP. In addition, self-powered photodetectors (PD) of FP-MP arrays with pyro-phototronic effects achieved detection beyond the band gap limit. Our results provide a new approach for bottom-up preparation of other crystalline allotropes of phosphorus.

Mixed-Dimensional van der Waals Heterostructure for High-Performance and Air-Stable Perovskite Nanowire Photodetectors.

An organic-inorganic hybrid perovskite nanowire (NW), CH3NH3PbI3, shows great potential for high-performance photodetectors due to its excellent photoresponse. However, the inefficient carrier collection between the one-dimensional (1D) NWs and metallic electrodes, as well as degradation of the perovskite, limits the viability of the CH3NH3PbI3 NWs for commercial production. Here, we demonstrate a photodetector with a mixed-dimensional van der Waals heterostructure of hexagonal boron nitride (hBN)/graphene (Gr)/1D CH3NH3PbI3, which exhibits excellent responsivity and specific detectivity of up to 558 A/W and 2.3 × 1012 Jones, owing to the improved carrier extraction at the electrical contact between Gr and the NW. As for the atomic encapsulation of hBN, the device is extremely robust and maintains its outstanding performance for more than 2 months when exposed to air. Moreover, benefitting from the 1D geometry of the CH3NH3PbI3 NW, our device is highly sensitive to polarized light. The mixed-dimensional van der Waals heterostructure, hBN/Gr/1D CH3NH3PbI3, would provide a novel idea and protocol for fabricating high-performance and air-stable photoelectronic devices based on organic-inorganic hybrid perovskite NWs.

Atomic-Scale Insights into the Interfacial Polarization Effect in the InGaN/GaN Heterostructure for Solar Cells.

The model system of the InGaN/GaN quantum wells (QWs), based on the first principles calculation, was chosen to understand the underlying mechanism of interfacial polarization and its synergic effect with the built-in electric field (Bef) at the p-n junction in solar cells (SLs). The polarized electric field (Pef) was generated due to the redistribution of electrons and holes at the interface; moreover, the Pef of InGaN/GaN heterostructure on the semipolar (01-11) GaN surface was consistent with that of on the N-polar (000-1) surface, which is on the lines of the Bef and favors the electron-hole separation efficiency in SLs. Furthermore, the growth of high-quality InGaN/GaN QWs on the semipolar (01-11) GaN surface was achieved. Such an atomic-scale investigation provides a fundamental understanding of the polarization charge-induced Pef and its interaction coupling with Bef at the p-n junction, which could be generalized to polar material-based SLs.