Novel Au/Cu2NiSnS4 Nano-Heterostructure: Synthesis, Structure, Heterojunction Band Offset and Alignment, and Interfacial Charge Transfer Dynamics.

Considering the importance of physics and chemistry at material interfaces, we have explored the coupling of multinary chalcogenide semiconductor Cu2NiSnS4 nanoparticles (CNTS NPs) for the first time with the noble metal (Au) to form Au-CNTS nano-heterostructures (NHSs). The Au-CNTS NHSs is synthesized by a simple facile hot injection method. Synergistic experimental and theoretical approaches are employed to characterize the structural, optical, and electrical properties of the Au-CNTS NHSs. The absorption spectra demonstrate enhanced and broadened optical absorption in the ultraviolet-visible-near-infrared (UV-Vis-NIR) region, which is corroborated by cyclic voltammetry (CV) readings. CV measurements show type II staggered band alignment, with a conduction band offset (CBO) of 0.21 and 0.23 eV at the Au-CNTS/CdS and CNTS/CdS interface, respectively. Complementary first-principles density functional theory (DFT) calculations predict the formation of a stable Au-CNTS NHSs, with the Au nanoparticle transferring its electrons to the CNTS. Moreover, our interface analysis using ultrafast transient absorption experiments demonstrate that the Au-CNTS NHSs facilitates efficient transport and separation of photoexcited charge carriers when compared to pristine CNTS. The transient measurements further reveal a plasmonic electronic transfer from the Au nanoparticle to CNTS. Our advanced analysis and findings will prompt investigations into new functional materials and their photo/electrocatalysis and optoelectronic device applications in the future.

Fabrication of ZnO Scaffolded CdS Nanostructured Photoanodes with Enhanced Photoelectrochemical Water Splitting Activity under Visible Light.

CdS, characterized by its comparatively narrow energy band gap (∼2.4 eV), is an appropriate material for prospective use as a photoanode in photoelectrochemical water splitting. Regrettably, it encounters several obstacles for practical and large-scale applications, including issues such as bulk carrier recombination and diminished conductivity. Here, we have tried to address these challenges by fabricating a novel photoelectrode (ZnO/CdS) composed of one-dimensional ZnO nanorods (NRs) decorated with two-dimensional CdS nanosheets (NSs). A facile two-step chemical method comprising electrodeposition along with chemical bath deposition is employed to synthesize the ZnO NRs, CdS NSs, and ZnO/CdS nanostructures. The prepared nanostructures have been investigated by UV-visible absorption spectroscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy. The fabricated ZnO/CdS nanostructures have shown enhanced photoelectrochemical properties due to the improvement of the semiconductor junction surface area and thereby enhanced visible light absorption. The incorporation of CdS NSs has been further found to promote the rate of the charge separation and transfer process. Subsequently, the fabricated ZnO/CdS photoelectrodes achieved a photocurrent conversion efficiency 3 times higher than that of a planar ZnO NR photoanode and showed excellent performance under visible light irradiation. The highest applied bias photon-to-current conversion efficiency (% ABPE) of about ∼0.63% has been obtained for the sample with thicker CdS NSs on ZnO NRs with a photocurrent density of ∼1.87 mA/cm2 under AM 1.5 G illumination. The newly synthesized nanostructures further demonstrate that the full photovoltaic capacity of nanomaterials is yet to be exhausted.

Unraveling Interface-Driven and Loss Mechanism-Centric Phenomena in 3D/2D Halide Perovskites: Prospects for Optoelectronic Applications.

In recent years, organic-inorganic metal halide perovskite solar cells (PSCs) have attracted considerable interest due to their remarkable and rapidly advancing efficiencies. Over the past decade, PSC efficiencies have significantly approached those of state-of-the-art silicon-based photovoltaics, making them a promising material. Currently, the scientific community widely recognizes the performance of 3D-PSCs and 2D-PSCs individually. However, when both are combined to form a heterostructure, the lattice and charge dynamics at the interface undergo a multitude of mechanisms that affect their performance. The interface between heterostructures facilitates the degradation of PSCs. The degradation pathways can be attributed to lattice distortions, inhomogeneous energy landscapes, interlayer ion migration, nonradiative recombination, and charge accumulation. This Review is dedicated to examining the phenomena that arise at the interface of 3D/2D halide perovskites and their related photophysical properties and loss mechanism processes. We mainly focus on the impact of lattice mismatch, energy level alignment, anomalous carrier dynamics, and loss mechanisms. We propose a "cause-impact-identify-rectify" approach to gain a comprehensive understanding of the ultrafast processes occurring within the material. Finally, we highlight the importance of advanced spectroscopic and imaging techniques in unraveling these intricate mechanisms. This discussion delves into the future possibilities of fabricating 3D/2D heterostructure-based optoelectronic devices, pushing the boundaries of performance across diverse fields. It envisions the creation of devices with unparalleled capabilities, exceeding the limitations of current technologies.

Interfacial band offset engineering with barium-doping towards enhanced performance of all inorganic CsPbI2Br perovskite solar cells.

This study investigates the incorporation of Ba2+ at a low concentration into CsPbI2Br, resulting in the formation of mixed CsPb1-xBaxI2Br perovskite films. Photovoltaic devices utilizing these Ba-doped CsPbI2Br (Ba-CsPbI2Br) perovskite films achieved a higher stabilized power conversion efficiency of 14.07% compared to 11.60% for pure CsPbI2Br films. First-principles density functional theory calculations indicate that the improved device performance can be attributed to the efficient transport of conduction electrons across the interface between Ba-CsPbI2Br and the TiO2 electron transporting layer (ETL). The Ba-CsPbI2Br/TiO2 interface exhibits a type-II staggered band alignment with a smaller conduction band offset (CBO) of 0.25 eV, in contrast to the CsPbI2Br/TiO2 interface with a CBO of 0.48 eV. The reduced CBO at the Ba-CsPbI2Br/TiO2 interface diminishes the barrier for conduction electrons to transfer from the Ba-CsPbI2Br layer to the TiO2 layer, facilitating efficient charge transport.

Regulated electrochemical performance of manganese oxide cathode for potassium-ion batteries: A combined experimental and first-principles density functional theory (DFT) investigation.

Potassium-ion batteries (KIBs) are promising energy storage devices owing to their low cost, environmental-friendly, and excellent K+ diffusion properties as a consequence of the small Stoke's radius. The evaluation of cathode materials for KIBs, which are perhaps the most favorable substitutes to lithium-ion batteries, is of exceptional importance. Manganese dioxide (α-MnO2) is distinguished by its tunnel structures and plenty of electroactive sites, which can host cations without causing fundamental structural breakdown. As a result of the satisfactory redox kinetics and diffusion pathways of K+ in the structure, α-MnO2 nanorods cathode prepared through hydrothermal method, reversibly stores K+ at a fast rate with a high capacity and stability. It has a first discharge capacity of 142 mAh/g at C/20, excellent rate execution up to 5C, and a long cycling performance with a demonstration of moderate capacity retention up to 100 cycles. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) simulations confirm that the K+ intercalation/deintercalation occurs through 0.46 K movement between MnIV/MnIII redox pairs. First-principles density functional theory (DFT) calculations predict a diffusion barrier of 0.31 eV for K+ through the 1D tunnel of α-MnO2 electrode, which is low enough to promote faster electrochemical kinetics. The nanorod structure of α-MnO2 facilitates electron conductive connection and provides a strong electrode-electrolyte interface for the cathode, resulting in a very consistent and prevalent execution cathode material for KIBs.

Improved photocatalytic activity of TiO2 nanoparticles through nitrogen and phosphorus co-doped carbon quantum dots: an experimental and theoretical study.

In this work, we develop a photocatalyst wherein nitrogen and phosphorus co-doped carbon quantum dots are scaffolded onto TiO2 nanoparticles (NPCQD/TiO2), denoted as NPCT hereafter. The developed NPCT photocatalyst exhibits an enhanced visible light photocatalytic hydrogen production of 533 µmol h-1 g-1 compared to nitrogen doped CQD/TiO2 (478 µmol h-1 g-1), phosphorus doped CQD/TiO2 (451 µmol h-1 g-1) and pure CQD/TiO2 (427 µmol h-1 g-1) photocatalysts. The enhanced photocatalytic activity of the NPCT photocatalyst is attributed to the excellent synergy between NPCQDs and TiO2 nanoparticles, which results in the creation of virtual energy levels, a decrease in work function and suppressed recombination rates, thereby increasing the lifetime of photogenerated electrons. A detailed mechanism is proposed for the enhancement in visible light hydrogen production by the NPCT photocatalyst from the experimental results, Mott-Schottky plots and ultraviolet photoelectron spectroscopy results. Further, first-principles density functional theory (DFT) simulations are carried out which predict the decrease in the work function and band gap, and the increase in the density of states of NPCT as the factors responsible for the observed enhancement in visible light photocatalytic hydrogen production.

Terbium-Doped and Dual-Passivated γ-CsPb(I1- x Brx )3 Inorganic Perovskite Solar Cells with Improved Air Thermal Stability and High Efficiency.

Realizing photoactive and thermodynamically stable all-inorganic perovskite solar cells (PSCs) remains a challenging task within halide perovskite photovoltaic (PV) research. Here, a dual strategy for realizing efficient inorganic mixed halide perovskite PV devices based on a terbium-doped solar absorber, that is, CsPb1- x Tbx I2 Br, is reported, which undertakes a bulk and surface passivation treatment in the form of CsPb1- x Tbx I2 Br quantum dots, to maintain a photoactive γ-phase under ambient conditions and with significantly improved operational stability. Devices fabricated from these air-processed perovskite thin films exhibit an air-stable power conversion efficiency (PCE) that reaches 17.51% (small-area devices) with negligible hysteresis and maintains >90% of the initial efficiency when operating for 600 h under harsh environmental conditions, stemming from the combined effects of the dual-protection strategy. This approach is further examined within large-area PSC modules (19.8 cm2 active area) to realize 10.94% PCE and >30 days ambient stability, as well as within low-bandgap γ-CsPb0.95 Tb0.05 I2.5 Br0.5 (Eg  = 1.73 eV) materials, yielding 19.01% (18.43% certified) PCE.

Exploring the emerging applications of the advanced 2-dimensional material borophene with its unique properties.

Borophene, a crystalline allotrope of monolayer boron, with a combination of triangular lattice and hexagonal holes, has stimulated wide interest in 2-dimensional materials and their applications. Although their properties are theoretically confirmed, they are yet to be explored and confirmed experimentally. In this review article, we present advancements in research on borophene, its synthesis, and unique properties, including its advantages for various applications with theoretical predictions. The uniqueness of borophene over graphene and other 2-dimensional (2D) materials is also highlighted along with their various structural stabilities. The strategy for its theoretical simulations, leading to the experimental synthesis, could also be helpful for the exploration of many newer 2D materials.

Enhanced Charge Carrier Separation and Improved Biexciton Yield at the p-n Junction of SnSe/CdSe Heterostructures: A Detailed Electrochemical and Ultrafast Spectroscopic Investigation.

Tin chalcogenides (SnX, X = S, Se)-based heterostructures (HSs) are promising materials for the construction of low-cost optoelectronic devices. Here, we report the synthesis of a SnSe/CdSe HS using the controlled cation exchange reaction. The (400) plane of SnSe and the (111) plane of CdSe confirm the formation of an interface between SnSe and CdSe. The Type I band alignment is estimated for the SnSe/CdSe HS with a small conduction band offset (CBO) of 0.72 eV through cyclic voltammetry measurements. Transient absorption (TA) studies demonstrate a drastic enhancement of the CdSe biexciton signal that points toward the hot carrier transfer from SnSe to CdSe in a short time scale. The fast growth and recovery of CdSe bleach in the presence of SnSe indicate charge transfer back to SnSe. The observed delocalization of carriers in these two systems is crucial for an optoelectronic device. Our findings provide new insights into the fabrication of cost-effective photovoltaic devices based on SnSe-based heterostructures.

Ternary Cu2SnS3: Synthesis, Structure, Photoelectrochemical Activity, and Heterojunction Band Offset and Alignment.

Ternary Cu2SnS3 (CTS) is an attractive nontoxic and earth-abundant absorber material with suitable optoelectronic properties for cost-effective photoelectrochemical applications. Herein, we report the synthesis of high-quality CTS nanoparticles (NPs) using a low-cost facile hot injection route, which is a very simple and nontoxic synthesis method. The structural, morphological, optoelectronic, and photoelectrochemical (PEC) properties and heterojunction band alignment of the as-synthesized CTS NPs have been systematically characterized using various state-of-the-art experimental techniques and atomistic first-principles density functional theory (DFT) calculations. The phase-pure CTS NPs confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses have an optical band gap of 1.1 eV and exhibit a random distribution of uniform spherical particles with size of approximately 15-25 nm as determined from high-resolution transmission electron microscopy (HR-TEM) images. The CTS photocathode exhibits excellent photoelectrochemical properties with PCE of 0.55% (fill factor (FF) = 0.26 and open circuit voltage (Voc) = 0.54 V) and photocurrent density of -3.95 mA/cm2 under AM 1.5 illumination (100 mW/cm2). Additionally, the PEC activities of CdS and ZnS NPs are investigated as possible photoanodes to create a heterojunction with CTS to enhance the PEC activity. CdS is demonstrated to exhibit a higher current density than ZnS, indicating that it is a better photoanode material to form a heterojunction with CTS. Consistently, we predict a staggered type-II band alignment at the CTS/CdS interface with a small conduction band offset (CBO) of 0.08 eV compared to a straddling type-I band alignment at the CTS/ZnS interface with a CBO of 0.29 eV. The observed small CBO at the type-II band aligned CTS/CdS interface points to efficient charge carrier separation and transport across the interface, which are necessary to achieve enhanced PEC activity. The facile CTS synthesis, PEC measurements, and heterojunction band alignment results provide a promising approach for fabricating next-generation Cu-based light-absorbing materials for efficient photoelectrochemical applications.

Revealing the electronic structure, heterojunction band offset and alignment of Cu2ZnGeSe4: a combined experimental and computational study towards photovoltaic applications.

Cu2ZnGeSe4 (CZGSe) is a promising earth-abundant and non-toxic semiconductor material for large-scale thin-film solar cell applications. Herein, we have employed a joint computational and experimental approach to characterize and assess the structural, optoelectronic, and heterojunction band offset and alignment properties of a CZGSe solar absorber. The CZGSe films were successfully prepared using DC-sputtering and e-beam evaporation systems and confirmed by XRD and Raman spectroscopy analyses. The CZGSe films exhibit a bandgap of 1.35 eV, as estimated from electrochemical cyclic voltammetry (CV) measurements and validated by first-principles density functional theory (DFT) calculations, which predicts a bandgap of 1.38 eV. A fabricated device based on the CZGSe as a light absorber and CdS as a buffer layer yields power conversion efficiency (PCE) of 4.4% with VOC of 0.69 V, FF of 37.15, and Jsc of 17.12 mA cm-2. Therefore, we suggest that interface and band offset engineering represent promising approaches to improve the performance of CZGSe devices by predicting a type-II staggered band alignment with a small conduction band offset of 0.18 eV at the CZGSe/CdS interface.

Implementing Dopant-Free Hole-Transporting Layers and Metal-Incorporated CsPbI2Br for Stable All-Inorganic Perovskite Solar Cells.

Mixed-halide CsPbI2Br perovskite is promising for efficient and thermally stable all-inorganic solar cells; however, the use of conventional antisolvent methods and additives-based hole-transporting layers (HTLs) currently hampers progress. Here, we have employed hot-air-assisted perovskite deposition in ambient condition to obtain high-quality photoactive CsPbI2Br perovskite films and have extended stable device operation using metal cation doping and dopant-free hole-transporting materials. Density functional theory calculations are used to study the structural and optoelectronic properties of the CsPbI2Br perovskite when it is doped with metal cations Eu2+ and In3+. We experimentally incorporated Eu2+ and In3+ metal ions into CsPbI2Br films and applied dopant-free copper(I) thiocyanate (CuSCN) and poly(3-hexylthiophene) (P3HT)-based materials as low-cost hole transporting layers, leading to record-high power conversion efficiencies of 15.27% and 15.69%, respectively, and a retention of >95% of the initial efficiency over 1600 h at 85 °C thermal stress.

High Stability and Long Cycle Life of Rechargeable Sodium-Ion Battery Using Manganese Oxide Cathode: A Combined Density Functional Theory (DFT) and Experimental Study.

Sodium-ion batteries (SIBs) can develop cost-effective and safe energy storage technology for substantial energy storage demands. In this work, we have developed manganese oxide (α-MnO2) nanorods for SIB applications. The crystal structure, which is crucial for high-performance energy storage, is examined systematically for the metal oxide cathode. The intercalation of sodium into the α-MnO2 matrix was studied using the theoretical density functional theory (DFT) studies. The DFT studies predict Na ions' facile diffusion kinetics through the MnO2 lattice with an attractively low diffusion barrier (0.21 eV). When employed as a cathode material for SIBs, MnO2 showed a moderate capacity (109 mAh·g-1 at C/20 current rate) and superior life cyclability (58.6% after 800 cycles) in NaPF6/EC+DMC (5% FEC) electrolyte. It shows a much higher capacity of 181 mAh·g-1 (C/20 current rate) in NaClO4/PC (5% FEC) electrolyte, though it suffers fast capacity fading (11.5% after 800 cycles). Our findings show that high crystallinity and hierarchical nanorod morphology of the MnO2 are responsible for better cycling performance in conjunction with fast and sustained charge-discharge behaviors.

Experimental and Theoretical Investigation of the Structural and Opto-electronic Properties of Fe-Doped Lead-Free Cs2 AgBiCl6 Double Perovskite.

Lead-free double perovskites have emerged as stable and non-toxic alternatives to Pb-halide perovskites. Herein, the synthesis of Fe-doped Cs2 AgBiCl6 lead-free double perovskites are reported that display blue emission using an antisolvent method. The crystal structure, morphology, optical properties, band structure, and stability of the Fe-doped double perovskites were investigated systematically. Formation of the Fe-doped Cs2 AgBiCl6 double perovskite is confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. XRD and thermo-gravimetric analysis (TGA) shows that the Cs2 AgBiCl6 double perovskite has high structural and thermal stability, respectively. Field emission scanning electron microscopy (FE-SEM) analysis revealed the formation of dipyramidal shape Cs2 AgBiCl6 crystals. Furthermore, energy-dispersive X-ray spectroscopy (EDS) mapping shows the overlapping of Cs, Bi, Ag, Fe, and Cl elements and homogenous incorporation of Fe in Cs2 AgBiCl6 double perovskite. The Fe-doped Cs2 AgBiCl6 double perovskite shows a strong absorption at 380 nm. It extends up to 700 nm, suggesting that sub-band gap states transition may originate from the surface defect of the doped perovskite material. The radiative kinetics of the crystals was studied using the time-correlated single-photon counting (TCSPC) technique. Lattice parameters and band gap value of the Fe-doped Cs2 AgBiCl6 double perovskites predicted by the density functional theory (DFT) calculations are confirmed by XRD and UV/Visible spectroscopy analysis. Time-dependent photo-response characteristics of the Fe-doped Cs2 AgBiCl6 double perovskite show fast response and recovery time of charge carriers. We believe that the successful incorporation of Fe in lead-free, environmentally friendly Cs2 AgBiCl6 double perovskite can open a new class of doped double perovskites with significant potential optoelectronics devices fabrication and photocatalytic applications.

Experimental and Theoretical Study into Interface Structure and Band Alignment of the Cu2Zn1-x Cd x SnS4 Heterointerface for Photovoltaic Applications.

To improve the constraints of kesterite Cu2ZnSnS4 (CZTS) solar cell, such as undesirable band alignment at p-n interfaces, bandgap tuning, and fast carrier recombination, cadmium (Cd) is introduced into CZTS nanocrystals forming Cu2Zn1-x Cd x SnS4 through cost-effective solution-based method without postannealing or sulfurization treatments. A synergetic experimental-theoretical approach was employed to characterize and assess the optoelectronic properties of Cu2Zn1-x Cd x SnS4 materials. Tunable direct band gap energy ranging from 1.51 to 1.03 eV with high absorption coefficient was demonstrated for the Cu2Zn1-x Cd x SnS4 nanocrystals with changing Zn/Cd ratio. Such bandgap engineering in Cu2Zn1-x Cd x SnS4 helps in effective carrier separation at interface. Ultrafast spectroscopy reveals a longer lifetime and efficient separation of photoexcited charge carriers in Cu2CdSnS4 (CCTS) nanocrystals compared to that of CZTS. We found that there exists a type-II staggered band alignment at the CZTS (CCTS)/CdS interface, from cyclic voltammetric (CV) measurements, corroborated by first-principles density functional theory (DFT) calculations, predicting smaller conduction band offset (CBO) at the CCTS/CdS interface as compared to the CZTS/CdS interface. These results point toward efficient separation of photoexcited carriers across the p-n junction in the ultrafast time scale and highlight a route to improve device performances.

ZnO/CuSCN Nano-Heterostructure as a Highly Efficient Field Emitter: a Combined Experimental and Theoretical Investigation.

We report the synthesis of two-dimensional porous ZnO nanosheets, CuSCN nanocoins, and ZnO/CuSCN nano-heterostructure thin films grown on fluorine-doped tin oxide substrates via two simple and low-cost solution chemical routes, i.e., chemical bath deposition and successive ionic layer adsorption and reaction methods. Detail characterizations regarding the structural, optoelectronic, and morphological properties have been carried out, which reveal high-quality and crystalline synthesized materials. Field emission (FE) investigations performed at room temperature with a base pressure of 1 × 10-8 mbar demonstrate superior FE performance of the ZnO/CuSCN nano-heterostructure compared to the isolated porous ZnO nanosheets and CuSCN nanocoins. For instance, the turn-on field required to draw a current density of 10 µA/cm2 is found to be 2.2, 1.1, and 0.7 V/µm for the ZnO, CuSCN, and ZnO/CuSCN nano-heterostructure, respectively. The observed significant improvement in the FE characteristics (ultralow turn-on field of 0.7 V/µm for an emission current density of 10 µA/cm2 and the achieved high current density of 2.2 mA/cm2 at a relatively low applied electric field of 1.8 V/µm) for the ZnO/CuSCN nano-heterostructure is superior to the isolated porous ZnO nanosheets, CuSCN nanocoins, and other reported semiconducting nano-heterostructures. Complementary first-principles density functional theory calculations predict a lower work function for the ZnO/CuSCN nano-heterostructure (4.58 eV), compared to the isolated ZnO (5.24 eV) and CuSCN (4.91 eV), validating the superior FE characteristics of the ZnO/CuSCN nano-heterostructure. The ZnO/CuSCN nanocomposite could provide a promising class of FE cathodes, flat panel displays, microwave tubes, and electron sources.

Enhanced Field Emission Properties of Au/SnSe Nano-heterostructure: A Combined Experimental and Theoretical Investigation.

We report the field emission properties of two-dimensional SnSe nanosheets (NSs) and Au/SnSe nano-heterostructure (NHS) prepared by a simple and economical route of one-pot colloidal and sputtering technique. Field Emission Scanning Electron Microscope (FESEM) analysis reveal surface protrusions and morphology modification of the SnSe NSs by Au deposition. By decorating the SnSe NSs with Au nanoparticles, significant improvement in field emission characteristics were observed. A significant reduction in the turn-on field from 2.25 V/µm for the SnSe NSs to 1.25 V/µm for the Au/SnSe NHS was observed. Emission current density of 300 µA/cm2 has been achieved at an applied field of 4.00 and 1.91 V/µm for SnSe NSs and Au/SnSe NHS, respectively. Analysis of the emission current as a function of time also demonstrated the robustness of the present Au/SnSe NHS. Consistent with the experimental data, our complementary first-principles DFT calculations predict lower work function for the Au/SnSe NHS compared to the SnSe NSs as the primary origin for improved field emission. The present study has evidently provided a rational heterostructure strategy for improving various field emission related applications via surface and electronic modifications of the nanostructures.

Uncovering the origin of enhanced field emission properties of rGO-MnO2 heterostructures: a synergistic experimental and computational investigation.

The unique structural merits of heterostructured nanomaterials including the electronic interaction, interfacial bonding and synergistic effects make them attractive for fabricating highly efficient optoelectronic devices. Herein, we report the synthesis of MnO2 nanorods and a rGO/MnO2 nano-heterostructure using low-cost hydrothermal and modified Hummers' methods, respectively. Detailed characterization and confirmation of the structural and morphological properties are done via X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Compared to the isolated MnO2 nanorods, the rGO/MnO2 nano-heterostructure exhibits impressive field emission (FE) performance in terms of the low turn-on field of 1.4 V µm-1 for an emission current density of 10 µA cm-2 and a high current density of 600 µA cm-2 at a relatively very low applied electric field of 3.1 V µm-1. The isolated MnO2 nanorods display a high turn-on field of 7.1 for an emission current density of 10 µA cm-2 and a low current density of 221 µA cm-2 at an applied field of 8.1 V µm-1. Besides the superior FE characteristics of the rGO/MnO2 nano-heterostructure, the emission current remains quite stable over the continuous 2 h period of measurement. The improvement of the FE characteristics of the rGO/MnO2 nano-heterostructure can be ascribed to the nanometric features and the lower work function (6.01 and 6.12 eV for the rGO with 8% and 16% oxygen content) compared to the isolated α-MnO2(100) surface (Φ = 7.22 eV) as predicted from complementary first-principles electronic structure calculations based on density functional theory (DFT) methods. These results suggest that an appropriate coupling of rGO with MnO2 nanorods would have a synergistic effect of lowering the electronic work function, resulting in a beneficial tuning of the FE characteristics.