A colloidal quantum dot photoelectrochemical cell based on a Cu-doped AgIn5S8-photoanode exhibits... more A colloidal quantum dot photoelectrochemical cell based on a Cu-doped AgIn5S8-photoanode exhibits promising photoelectrochemical activity for high-efficiency hydrogen production due to the Cu-doping effect.
The AgInS 2 colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide... more The AgInS 2 colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide band gap for photoelectrochemical (PEC) solar-driven hydrogen (H 2 ) evolution. However, the unsuitable energy band structure still forms undesired energy barriers and leads to serious charge carrier recombination with low solar to hydrogen conversion efficiency. Here, we propose to use the ZnS shell for defect passivation and Cu ion doping for band structure engineering to design and synthesize a series of Cu x Ag 1-x InS 2 /ZnS CQDs. ZnS shell-assisted defect passivation suppresses charge carrier recombination because of the formation of the core/shell heterojunction interface, enhancing the performance of PEC devices with better charge separation and stability. More importantly, the tunable Cu doping concentration in AgInS 2 CQDs leads to the shift of the quantum dot band alignment, which greatly promotes the interfacial charge separation and transfer. As a result, Cu x Ag 1-x InS 2 /ZnS CQD photoanodes for PEC cells exhibit an enhanced photocurrent of 5.8 mA cm -2 at 0.8 V versus the RHE, showing excellent photoelectrocatalytic activity for H 2 production with greater chemical-/photostability.
Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graph... more Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C_3N_4, nitrogenated holey grahpene C_2N, polyaniline C_3N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C_9N_4 stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C_9N_4 is found to be a 2D nodal-line semimetal (NLSM). The nodal line in C_9N_4 forms a closed ring centered at Γ point, which originates from the pz orbitals of both C and N. The linear crossing happens right at Fermi level contributed by two sets of dispersive Kagome and Dirac bands, which is robust due to negligible spin-orbital-coupling (SOC) in C and N. Besides, it is revealed that the formation of nodal ring is of accidental band degeneracy in n...
In this paper, a framework of w_1, w_2, R classification for constructing the graphene nanomesh (... more In this paper, a framework of w_1, w_2, R classification for constructing the graphene nanomesh (GNM) of zigzag-edged hexagonal nanohole is systematically built. The three integer indexes w_1, w_2, and R indicate the distances between two neighboring sides of nanoholes in two directions and the nanohole size respectively, which leading to a straightforward gap opening criteria, i.e., w_1+w_2-R=3n+1,n is integer, steered via DFT band structure calculations.The guiding rule indicates that the semimetallic and semiconducting variation is consistent with a peculiar sequence "010" and "100" ("0"/"1" represent gap closure/opening) with a period of 3 for odd and even w_1 respectively. The periodic nanoperforation induced gap sizes agreewith a linear fitting with a smaller sqrt(N_rem )/N_tot ratio, while deviates from that when (w_1+w_2)<R+1. Particularly, the p, 1, p and 1, q, q structures demonstrate each unique scaling rule pertaining to the nan...
Strain analysis has significance both for tailoring material properties and designing nanoscale d... more Strain analysis has significance both for tailoring material properties and designing nanoscale devices. In particular, strain plays a vital role in engineering the growth thermodynamics and kinetics and is applicable for designing optoelectronic devices. In this paper, we present a methodology for establishing the relationship between elastic bond constants and measurable parameters, i.e., Poisson’s ratio ν and systematic elastic constant K. At the atomistic level, this approach is within the framework of linear elastic theory and encompasses the neighbor interactions when an atom is introduced to stress. Departing from the force equilibrium equations, the relationships between ν, K, and spring constants are successfully established. Both the two-dimensional (2D) square lattice and common three-dimensional (3D) structures are taken into account in the procedure for facilitating, bridging the gap between structural complexity and numerical experiments. A new direction for understand...
Journal of Electronic Science and Technology, 2021
By using physical vapor deposition (PVD) to grow metallic nanorods, the characteristic length is ... more By using physical vapor deposition (PVD) to grow metallic nanorods, the characteristic length is controllable, which can be identified by two different growth modes: Mode I and Mode II. In Mode I, the growth of metallic nanorods is dominated by the monolayer surface steps. Whereas in Mode II, the growth mechanism is mainly determined by the multilayer surface steps. In this work, we focused on the analysis of the physical process of Mode I, in which the adatoms diffuse on the monolayer surface at beginning, then diffuse down to the next monolayer surface, and finally result in the metallic nanorods growth. Based on the physical process, both the variations of the characteristic length and the numerical solutions were theoretically proposed. In addition, the two-dimensional (2D) lattice kinetic Monte Carlo simulations were employed to verify the theoretical derivation of the metallic nanorods growth. Our results pay a new way for modifying the performance of metallic nanorods-based a...
Two-dimensional hexagonal boron nitride (h-BN) single crystals with various shapes have been synt... more Two-dimensional hexagonal boron nitride (h-BN) single crystals with various shapes have been synthesized by chemical vapor deposition over the past several years. Here we report the formation of three-leaf dart (3LD)-shaped single crystals of h-BN on Cu foil by atmospheric-pressure chemical vapor deposition. The leaves of the 3LD-shaped h-BN are as long as 18 {\mu}m and their edges are smooth armchair on one side and stepped armchair on the other. Careful analysis revealed that surface oxygen plays an important role in the formation of the 3LD shape. Oxygen suppressed h-BN nucleation by passivating Cu surface active sites and lowered the edge attachment energy, which caused the growth kinetics to change to a diffusion-controlled mode.
In a market-based financial system, banking and capital market developments are inseparable, and ... more In a market-based financial system, banking and capital market developments are inseparable, and funding conditions are closely tied to fluctuations in the leverage of market-based financial intermediaries. Offering a window on liquidity, the balance sheet growth of broker-dealers provides a sense of the availability of credit. Contractions of broker-dealer balance sheets have tended to precede declines in real economic growth, even before the current turmoil. For this reason, balance sheet quantities of market-based financial intermediaries are important macroeconomic state variables for the conduct of monetary policy.
Correction for ‘Chlorine-doped SnO2 hydrophobic surfaces for large grain perovskite solar cells’ ... more Correction for ‘Chlorine-doped SnO2 hydrophobic surfaces for large grain perovskite solar cells’ by Wenxiao Gong et al., J. Mater. Chem. C, 2020, DOI: 10.1039/d0tc00515k.
Both wetting and non-wetting tin oxide SnO2 were spin-coated and the non-wetting electron transpo... more Both wetting and non-wetting tin oxide SnO2 were spin-coated and the non-wetting electron transport layer demonstrated a larger perovskite and higher power conversion efficiency.
HIGHLIGHTS • The tunable mechanisms of lateral heterostructures on both homogeneous junctions and... more HIGHLIGHTS • The tunable mechanisms of lateral heterostructures on both homogeneous junctions and heterogeneous junctions are summarized. • Electronic and photoelectronic devices with lateral heterostructures have been discussed. • Different types of contacts of 2D lateral heterostructures are classified. • Recent developments in synthesis and nanofabrication technologies of 2D lateral heterostructures are reviewed. ABSTRACT Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from twodimensional (2D) materials. A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials. These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences. Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures; the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties. In this review, we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction, where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials. Afterward, we discuss the applications and experimental synthesis of lateral 2D heterostructures. Moreover, a perspective on lateral 2D heterostructures is given at the end.
Massive efforts have been devoted to enhancing performances of Li-S batteries to meet the require... more Massive efforts have been devoted to enhancing performances of Li-S batteries to meet the requirements of practical applications. However, problems remain in enhancing the energy density and improving the cycle life. We present a free-standing structure of walnut-shaped VS 4 nanosites combine with carbon nanotubes (NTs) as cathodes. In this framework, NT arrays provide high surface area and conductivity for high sulfur loadings, and VS 4 nanosites facilitate trapping and catalytic conversions of lithium polysulfides. The synergistic effects of free-standing NT arrays and VS 4 nanosites have enabled high rate capability up to 6 C and longterm cycling with a low decay rate of 0.037% up to 1200 cycles at 2 C. Moreover, the designed cathode can achieve high areal capacities up to ∼13 mAh•cm -2 and estimated gravimetric energy density of 243.4 Wh• kg -1 at a system level, demonstrating great potential in practical applications of Li-S batteries.
Abstract Developing novel low-cost and efficient electron transport layer (ETL) materials for hig... more Abstract Developing novel low-cost and efficient electron transport layer (ETL) materials for high-efficiency planar heterojunction perovskite solar cells (PSCs) still remains challenges. Herein, we report a low-temperature colloid-synthesized and solution-deposited strontium stannate SrSnO3 (SSO) perovskite oxide nanoparticle can be an effective alternative ETL. More importantly, the introduction of yttrium dopant results in a significant improvement in the optoelectronic properties of yttrium-doped SrSnO3 (YSSO), exhibiting higher electron conductivity and faster electron transfer, as well as better band alignment at ETL/perovskite interface compare to undoped SSO, which is also supported by theory calculation. Consequently, these factors boost all photovoltaic performance parameters, leading to an improvement in the efficiency of planar PSCs. The resulting YSSO-based PSCs exhibit an average efficiency of 17.8% and a maximum power conversion efficiency of 19.0% with the significant reduction of J–V hysteresis, and those devices show high long-term stability as well. Our findings provide the full potential of the perovskite oxide toward future photovoltaic applications, especially for cost-efficient planar PSCs.
Organic–inorganic CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbCl3 perovskites possess outstanding microwa... more Organic–inorganic CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbCl3 perovskites possess outstanding microwave absorbability with high reflectance loss values.
Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graph... more Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C 3 N 4 , nitrogenated holey grahpene C 2 N, polyaniline C 3 N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C 9 N 4 stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C 9 N 4 is found to be a 2D nodal-line semimetal (NLSM). The nodal line in C 9 N 4 forms a closed ring centered at point, which originates from the p z orbitals of both C and N. The linear crossing happens right at Fermi level contributed by two sets of dispersive Kagome 2 and Dirac bands, which is robust due to negligible spin-orbital-coupling (SOC) in C and N. Besides, it is revealed that the formation of nodal ring is of accidental band degeneracy in nature induced by the chemical potential difference of C and N, as validated by a single orbital tight-binding model, rather than protected by crystal in-plane mirror symmetry or band topology. Interestingly, a new structure of nodal line, i.e., nodal-cylinder, is found in momentum space for AA-stacking C 9 N 4. Our results imply possible functionalization for a novel metal-free C-N covalent network with interesting semimetallic properties.
We report a simple solution route for preparing a sGO-PEDOT composite HTL by combining solution-p... more We report a simple solution route for preparing a sGO-PEDOT composite HTL by combining solution-processable sGO with commercialized PEDOT:PSS solution. The PSCs based on these sGO-PEDOT composite HTLs were systematically investigated.
Both TiO2 and SnO2 as electron transport layers (ETLs) are the most successful at producing high-... more Both TiO2 and SnO2 as electron transport layers (ETLs) are the most successful at producing high-efficiency perovskite solar cells (PSCs). Unfortunately, these layers usually require multiple treatments to improve device performance, especially for TiO2-based planar PSCs. Here, a simple, one-step, solution-based method is introduced for fabricating a TiO2/SnO2 nanocomposite ETL. Compared to a pristine TiO2 layer, partial incorporation of SnO2 nanoparticles in a thin compact TiO2 layer contributes to high electrical conductivity and suitable band-level alignment at the ETL/perovskite interface. Using the optimized TiO2/SnO2 nanocomposite ETL, methylammonium lead halide perovskite CH3NH3PbI3-based PSCs exhibit the champion efficiency of 16.8% (area, 0.13 cm2) with less current density–voltage (J–V) hysteresis, which is significantly superior to that of TiO2-based PSCs. Our work highlights that the successful use of TiO2/SnO2 nanocomposite ETL can offer an efficient method for further improvement of the perf...
Abstract Organo-lead perovskite materials as light harvesters have represented a hot field of res... more Abstract Organo-lead perovskite materials as light harvesters have represented a hot field of research on high-efficiency perovskite solar cells. In such cells, the quality of organo-lead perovskite films is most critial to device performance, essentially affected by varying halide composition. Meanwhile, the understanding of formation mechanisms and basic properties of these hybrid perovskites is still ongoing. Herein, we report a one-step solution-processing strategy to investigate the role of precursor in the context of hybrid perovskites, in which the molar ratio of the methylammonium compound and lead salts is closely correlated to the characteristics of the hybrid perovskite films. We investigate the molar ratio dependence of the mixed-halides incorporation of three organolead trihalide perovskite absorbers, CH 3 NH 3 PbI 3−a Br a , CH 3 NH 3 PbI 3−a Cl a and CH 3 NH 3 PbBr 3−a Cl a , and compare them with three pure (CH 3 NH 3 PbI 3 , CH 3 NH 3 PbBr 3 , and CH 3 NH 3 PbCl 3 ) perovskites. We find the versatility of the hybrid perovskites affected by excess organic compounds. Specifically, the synergistic effect of the mixed-halides in tuning perovskite composition demonstrated that the different perovskite compositions deserved more in-depth understanding from with the varying of the crystal transformation, morphological framework, thermal decomposition and optical performance of the hybrid perovskites. Moreover, this work provides visual evidence for the design of the mixed halide perovskites based on these hybrids, which paves a way for improvements with selective properties in lead halide perovskite-based devices.
In this paper, a framework of {w 1 , w 2 , R} classification for constructing the graphene nanome... more In this paper, a framework of {w 1 , w 2 , R} classification for constructing the graphene nanomesh (GNM) of zigzag-edged hexagonal nanohole is systematically built. The three integer indexes w 1 , w 2 , and R indicate the distances between two neighboring sides of nanoholes in two directions and the nanohole size respectively, which leading to a straightforward gap opening criteria, i.e., 1 2 3 1, w w R n n + − = + ∈ , steered via DFT band structure calculations. The guiding rule indicates that the semimetallic and semiconducting variation is consistent with a peculiar sequence "010" and "100" ("0"/"1" represent gap closure/opening) with a period of 3 for odd and even w 1 respectively. The periodic nanoperforation induced gap sizes agreewith a linear fitting with a smaller � � ratio, while deviates from that when 1 2 () 1 w w R + < +. Particularly, the {p, 1, p} and {1, q, q} structures demonstrate each unique scaling rule pertaining to the nanohole size only when n is set to zero. Furthermore, the coexistence of Dirac and flat bands is observed for {1, q, q} and {1, 1, m} structures, which is sensitive to the atomic patters.
A thickness dependent band gap is commonly found in layered two-dimensional (2D) materials. Here,... more A thickness dependent band gap is commonly found in layered two-dimensional (2D) materials. Here, using a C3N bilayer as a prototypical model, we systematically investigated the evolution of a band gap from a single layer to a bilayer using first principles calculations and tight binding modeling. We show that in addition to the widely known effect of interlayer hopping, de-charge transfer also plays an important role in tuning the band gap. The de-charge transfer is defined with reference to the charge states of atoms in the single layer without stacking, which shifts the energy level and modifies the band gap. Together with band edge splitting induced by the interlayer hopping, the energy level shifting caused by the de-charge transfer determines the size of the band gap in bilayer C3N. Our finding, applicable to other 2D semiconductors, provides an alternative approach for realizing band gap engineering in 2D materials.
A colloidal quantum dot photoelectrochemical cell based on a Cu-doped AgIn5S8-photoanode exhibits... more A colloidal quantum dot photoelectrochemical cell based on a Cu-doped AgIn5S8-photoanode exhibits promising photoelectrochemical activity for high-efficiency hydrogen production due to the Cu-doping effect.
The AgInS 2 colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide... more The AgInS 2 colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide band gap for photoelectrochemical (PEC) solar-driven hydrogen (H 2 ) evolution. However, the unsuitable energy band structure still forms undesired energy barriers and leads to serious charge carrier recombination with low solar to hydrogen conversion efficiency. Here, we propose to use the ZnS shell for defect passivation and Cu ion doping for band structure engineering to design and synthesize a series of Cu x Ag 1-x InS 2 /ZnS CQDs. ZnS shell-assisted defect passivation suppresses charge carrier recombination because of the formation of the core/shell heterojunction interface, enhancing the performance of PEC devices with better charge separation and stability. More importantly, the tunable Cu doping concentration in AgInS 2 CQDs leads to the shift of the quantum dot band alignment, which greatly promotes the interfacial charge separation and transfer. As a result, Cu x Ag 1-x InS 2 /ZnS CQD photoanodes for PEC cells exhibit an enhanced photocurrent of 5.8 mA cm -2 at 0.8 V versus the RHE, showing excellent photoelectrocatalytic activity for H 2 production with greater chemical-/photostability.
Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graph... more Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C_3N_4, nitrogenated holey grahpene C_2N, polyaniline C_3N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C_9N_4 stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C_9N_4 is found to be a 2D nodal-line semimetal (NLSM). The nodal line in C_9N_4 forms a closed ring centered at Γ point, which originates from the pz orbitals of both C and N. The linear crossing happens right at Fermi level contributed by two sets of dispersive Kagome and Dirac bands, which is robust due to negligible spin-orbital-coupling (SOC) in C and N. Besides, it is revealed that the formation of nodal ring is of accidental band degeneracy in n...
In this paper, a framework of w_1, w_2, R classification for constructing the graphene nanomesh (... more In this paper, a framework of w_1, w_2, R classification for constructing the graphene nanomesh (GNM) of zigzag-edged hexagonal nanohole is systematically built. The three integer indexes w_1, w_2, and R indicate the distances between two neighboring sides of nanoholes in two directions and the nanohole size respectively, which leading to a straightforward gap opening criteria, i.e., w_1+w_2-R=3n+1,n is integer, steered via DFT band structure calculations.The guiding rule indicates that the semimetallic and semiconducting variation is consistent with a peculiar sequence "010" and "100" ("0"/"1" represent gap closure/opening) with a period of 3 for odd and even w_1 respectively. The periodic nanoperforation induced gap sizes agreewith a linear fitting with a smaller sqrt(N_rem )/N_tot ratio, while deviates from that when (w_1+w_2)<R+1. Particularly, the p, 1, p and 1, q, q structures demonstrate each unique scaling rule pertaining to the nan...
Strain analysis has significance both for tailoring material properties and designing nanoscale d... more Strain analysis has significance both for tailoring material properties and designing nanoscale devices. In particular, strain plays a vital role in engineering the growth thermodynamics and kinetics and is applicable for designing optoelectronic devices. In this paper, we present a methodology for establishing the relationship between elastic bond constants and measurable parameters, i.e., Poisson’s ratio ν and systematic elastic constant K. At the atomistic level, this approach is within the framework of linear elastic theory and encompasses the neighbor interactions when an atom is introduced to stress. Departing from the force equilibrium equations, the relationships between ν, K, and spring constants are successfully established. Both the two-dimensional (2D) square lattice and common three-dimensional (3D) structures are taken into account in the procedure for facilitating, bridging the gap between structural complexity and numerical experiments. A new direction for understand...
Journal of Electronic Science and Technology, 2021
By using physical vapor deposition (PVD) to grow metallic nanorods, the characteristic length is ... more By using physical vapor deposition (PVD) to grow metallic nanorods, the characteristic length is controllable, which can be identified by two different growth modes: Mode I and Mode II. In Mode I, the growth of metallic nanorods is dominated by the monolayer surface steps. Whereas in Mode II, the growth mechanism is mainly determined by the multilayer surface steps. In this work, we focused on the analysis of the physical process of Mode I, in which the adatoms diffuse on the monolayer surface at beginning, then diffuse down to the next monolayer surface, and finally result in the metallic nanorods growth. Based on the physical process, both the variations of the characteristic length and the numerical solutions were theoretically proposed. In addition, the two-dimensional (2D) lattice kinetic Monte Carlo simulations were employed to verify the theoretical derivation of the metallic nanorods growth. Our results pay a new way for modifying the performance of metallic nanorods-based a...
Two-dimensional hexagonal boron nitride (h-BN) single crystals with various shapes have been synt... more Two-dimensional hexagonal boron nitride (h-BN) single crystals with various shapes have been synthesized by chemical vapor deposition over the past several years. Here we report the formation of three-leaf dart (3LD)-shaped single crystals of h-BN on Cu foil by atmospheric-pressure chemical vapor deposition. The leaves of the 3LD-shaped h-BN are as long as 18 {\mu}m and their edges are smooth armchair on one side and stepped armchair on the other. Careful analysis revealed that surface oxygen plays an important role in the formation of the 3LD shape. Oxygen suppressed h-BN nucleation by passivating Cu surface active sites and lowered the edge attachment energy, which caused the growth kinetics to change to a diffusion-controlled mode.
In a market-based financial system, banking and capital market developments are inseparable, and ... more In a market-based financial system, banking and capital market developments are inseparable, and funding conditions are closely tied to fluctuations in the leverage of market-based financial intermediaries. Offering a window on liquidity, the balance sheet growth of broker-dealers provides a sense of the availability of credit. Contractions of broker-dealer balance sheets have tended to precede declines in real economic growth, even before the current turmoil. For this reason, balance sheet quantities of market-based financial intermediaries are important macroeconomic state variables for the conduct of monetary policy.
Correction for ‘Chlorine-doped SnO2 hydrophobic surfaces for large grain perovskite solar cells’ ... more Correction for ‘Chlorine-doped SnO2 hydrophobic surfaces for large grain perovskite solar cells’ by Wenxiao Gong et al., J. Mater. Chem. C, 2020, DOI: 10.1039/d0tc00515k.
Both wetting and non-wetting tin oxide SnO2 were spin-coated and the non-wetting electron transpo... more Both wetting and non-wetting tin oxide SnO2 were spin-coated and the non-wetting electron transport layer demonstrated a larger perovskite and higher power conversion efficiency.
HIGHLIGHTS • The tunable mechanisms of lateral heterostructures on both homogeneous junctions and... more HIGHLIGHTS • The tunable mechanisms of lateral heterostructures on both homogeneous junctions and heterogeneous junctions are summarized. • Electronic and photoelectronic devices with lateral heterostructures have been discussed. • Different types of contacts of 2D lateral heterostructures are classified. • Recent developments in synthesis and nanofabrication technologies of 2D lateral heterostructures are reviewed. ABSTRACT Recent developments in synthesis and nanofabrication technologies offer the tantalizing prospect of realizing various applications from twodimensional (2D) materials. A revolutionary development is to flexibly construct many different kinds of heterostructures with a diversity of 2D materials. These 2D heterostructures play an important role in semiconductor and condensed matter physics studies and are promising candidates for new device designs in the fields of integrated circuits and quantum sciences. Theoretical and experimental studies have focused on both vertical and lateral 2D heterostructures; the lateral heterostructures are considered to be easier for planner integration and exhibit unique electronic and photoelectronic properties. In this review, we give a summary of the properties of lateral heterostructures with homogeneous junction and heterogeneous junction, where the homogeneous junctions have the same host materials and the heterogeneous junctions are combined with different materials. Afterward, we discuss the applications and experimental synthesis of lateral 2D heterostructures. Moreover, a perspective on lateral 2D heterostructures is given at the end.
Massive efforts have been devoted to enhancing performances of Li-S batteries to meet the require... more Massive efforts have been devoted to enhancing performances of Li-S batteries to meet the requirements of practical applications. However, problems remain in enhancing the energy density and improving the cycle life. We present a free-standing structure of walnut-shaped VS 4 nanosites combine with carbon nanotubes (NTs) as cathodes. In this framework, NT arrays provide high surface area and conductivity for high sulfur loadings, and VS 4 nanosites facilitate trapping and catalytic conversions of lithium polysulfides. The synergistic effects of free-standing NT arrays and VS 4 nanosites have enabled high rate capability up to 6 C and longterm cycling with a low decay rate of 0.037% up to 1200 cycles at 2 C. Moreover, the designed cathode can achieve high areal capacities up to ∼13 mAh•cm -2 and estimated gravimetric energy density of 243.4 Wh• kg -1 at a system level, demonstrating great potential in practical applications of Li-S batteries.
Abstract Developing novel low-cost and efficient electron transport layer (ETL) materials for hig... more Abstract Developing novel low-cost and efficient electron transport layer (ETL) materials for high-efficiency planar heterojunction perovskite solar cells (PSCs) still remains challenges. Herein, we report a low-temperature colloid-synthesized and solution-deposited strontium stannate SrSnO3 (SSO) perovskite oxide nanoparticle can be an effective alternative ETL. More importantly, the introduction of yttrium dopant results in a significant improvement in the optoelectronic properties of yttrium-doped SrSnO3 (YSSO), exhibiting higher electron conductivity and faster electron transfer, as well as better band alignment at ETL/perovskite interface compare to undoped SSO, which is also supported by theory calculation. Consequently, these factors boost all photovoltaic performance parameters, leading to an improvement in the efficiency of planar PSCs. The resulting YSSO-based PSCs exhibit an average efficiency of 17.8% and a maximum power conversion efficiency of 19.0% with the significant reduction of J–V hysteresis, and those devices show high long-term stability as well. Our findings provide the full potential of the perovskite oxide toward future photovoltaic applications, especially for cost-efficient planar PSCs.
Organic–inorganic CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbCl3 perovskites possess outstanding microwa... more Organic–inorganic CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbCl3 perovskites possess outstanding microwave absorbability with high reflectance loss values.
Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graph... more Carbon nitride compounds have emerged recently as a prominent member of 2D materials beyond graphene. The experimental realizations of 2D graphitic carbon nitride g-C 3 N 4 , nitrogenated holey grahpene C 2 N, polyaniline C 3 N have shown their promising potential in energy and environmental applications. In this work, we predict a new type of carbon nitride network with a C 9 N 4 stoichiometry from first principle calculations. Unlike common C-N compounds and covalent organic frameworks (COFs), which are typically insulating, surprisingly C 9 N 4 is found to be a 2D nodal-line semimetal (NLSM). The nodal line in C 9 N 4 forms a closed ring centered at point, which originates from the p z orbitals of both C and N. The linear crossing happens right at Fermi level contributed by two sets of dispersive Kagome 2 and Dirac bands, which is robust due to negligible spin-orbital-coupling (SOC) in C and N. Besides, it is revealed that the formation of nodal ring is of accidental band degeneracy in nature induced by the chemical potential difference of C and N, as validated by a single orbital tight-binding model, rather than protected by crystal in-plane mirror symmetry or band topology. Interestingly, a new structure of nodal line, i.e., nodal-cylinder, is found in momentum space for AA-stacking C 9 N 4. Our results imply possible functionalization for a novel metal-free C-N covalent network with interesting semimetallic properties.
We report a simple solution route for preparing a sGO-PEDOT composite HTL by combining solution-p... more We report a simple solution route for preparing a sGO-PEDOT composite HTL by combining solution-processable sGO with commercialized PEDOT:PSS solution. The PSCs based on these sGO-PEDOT composite HTLs were systematically investigated.
Both TiO2 and SnO2 as electron transport layers (ETLs) are the most successful at producing high-... more Both TiO2 and SnO2 as electron transport layers (ETLs) are the most successful at producing high-efficiency perovskite solar cells (PSCs). Unfortunately, these layers usually require multiple treatments to improve device performance, especially for TiO2-based planar PSCs. Here, a simple, one-step, solution-based method is introduced for fabricating a TiO2/SnO2 nanocomposite ETL. Compared to a pristine TiO2 layer, partial incorporation of SnO2 nanoparticles in a thin compact TiO2 layer contributes to high electrical conductivity and suitable band-level alignment at the ETL/perovskite interface. Using the optimized TiO2/SnO2 nanocomposite ETL, methylammonium lead halide perovskite CH3NH3PbI3-based PSCs exhibit the champion efficiency of 16.8% (area, 0.13 cm2) with less current density–voltage (J–V) hysteresis, which is significantly superior to that of TiO2-based PSCs. Our work highlights that the successful use of TiO2/SnO2 nanocomposite ETL can offer an efficient method for further improvement of the perf...
Abstract Organo-lead perovskite materials as light harvesters have represented a hot field of res... more Abstract Organo-lead perovskite materials as light harvesters have represented a hot field of research on high-efficiency perovskite solar cells. In such cells, the quality of organo-lead perovskite films is most critial to device performance, essentially affected by varying halide composition. Meanwhile, the understanding of formation mechanisms and basic properties of these hybrid perovskites is still ongoing. Herein, we report a one-step solution-processing strategy to investigate the role of precursor in the context of hybrid perovskites, in which the molar ratio of the methylammonium compound and lead salts is closely correlated to the characteristics of the hybrid perovskite films. We investigate the molar ratio dependence of the mixed-halides incorporation of three organolead trihalide perovskite absorbers, CH 3 NH 3 PbI 3−a Br a , CH 3 NH 3 PbI 3−a Cl a and CH 3 NH 3 PbBr 3−a Cl a , and compare them with three pure (CH 3 NH 3 PbI 3 , CH 3 NH 3 PbBr 3 , and CH 3 NH 3 PbCl 3 ) perovskites. We find the versatility of the hybrid perovskites affected by excess organic compounds. Specifically, the synergistic effect of the mixed-halides in tuning perovskite composition demonstrated that the different perovskite compositions deserved more in-depth understanding from with the varying of the crystal transformation, morphological framework, thermal decomposition and optical performance of the hybrid perovskites. Moreover, this work provides visual evidence for the design of the mixed halide perovskites based on these hybrids, which paves a way for improvements with selective properties in lead halide perovskite-based devices.
In this paper, a framework of {w 1 , w 2 , R} classification for constructing the graphene nanome... more In this paper, a framework of {w 1 , w 2 , R} classification for constructing the graphene nanomesh (GNM) of zigzag-edged hexagonal nanohole is systematically built. The three integer indexes w 1 , w 2 , and R indicate the distances between two neighboring sides of nanoholes in two directions and the nanohole size respectively, which leading to a straightforward gap opening criteria, i.e., 1 2 3 1, w w R n n + − = + ∈ , steered via DFT band structure calculations. The guiding rule indicates that the semimetallic and semiconducting variation is consistent with a peculiar sequence "010" and "100" ("0"/"1" represent gap closure/opening) with a period of 3 for odd and even w 1 respectively. The periodic nanoperforation induced gap sizes agreewith a linear fitting with a smaller � � ratio, while deviates from that when 1 2 () 1 w w R + < +. Particularly, the {p, 1, p} and {1, q, q} structures demonstrate each unique scaling rule pertaining to the nanohole size only when n is set to zero. Furthermore, the coexistence of Dirac and flat bands is observed for {1, q, q} and {1, 1, m} structures, which is sensitive to the atomic patters.
A thickness dependent band gap is commonly found in layered two-dimensional (2D) materials. Here,... more A thickness dependent band gap is commonly found in layered two-dimensional (2D) materials. Here, using a C3N bilayer as a prototypical model, we systematically investigated the evolution of a band gap from a single layer to a bilayer using first principles calculations and tight binding modeling. We show that in addition to the widely known effect of interlayer hopping, de-charge transfer also plays an important role in tuning the band gap. The de-charge transfer is defined with reference to the charge states of atoms in the single layer without stacking, which shifts the energy level and modifies the band gap. Together with band edge splitting induced by the interlayer hopping, the energy level shifting caused by the de-charge transfer determines the size of the band gap in bilayer C3N. Our finding, applicable to other 2D semiconductors, provides an alternative approach for realizing band gap engineering in 2D materials.
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Papers by Haiyuan Chen