Leveraging the phononic sensitivity and scalability of nano‐biointerfaces has accelerated the gro... more Leveraging the phononic sensitivity and scalability of nano‐biointerfaces has accelerated the growth of unique and versatile biosensors. Graphene has the properties of a near‐ideal signal transducer, due to the strong coupling between its interfacial and phononic properties. This enables sensitive yet quick detection of surface interactions on graphene via Raman spectral analysis. The Raman‐active vibrational bands of graphene are demonstrated to be sensitive to structural, electrical, and interfacial modifications. This sensitivity is attributed to graphene's electron–phonon coupling and high quantum capacitance. The fundamental understanding of graphene phonons is crucial for developing reliable platforms for disease and infectious agent detection. This review provides a mechanistic explanation of these phenomena at the interface between graphene and various biosystems (including cancerous, bacterial, viral, and biophysical specimens) to set the foundation for next‐generation ...
Abstract The realization of unique scientific phenomena in two-dimensional nanomaterials (2DNMs) ... more Abstract The realization of unique scientific phenomena in two-dimensional nanomaterials (2DNMs) has led to their applications in several electronic fields; making it imperative to understand the conduction mechanism of charge carriers in such systems. Though several studies have been conducted on 2DNMs with pristine crystallinity, the inevitable presence of defects in the crystals requires careful consideration of their effect on 2DNMs’ electrical behavior. Here, we outline the effects of chemical, structural, substrate-induced defects and disorder on the conduction mechanism within 2DNMs, particularly graphene derivatives and MoS2. The conduction mechanisms discussed in this work are thermally activated conduction, nearest neighbor hopping, Efros-Shklovskii variable range hopping, and Mott variable range hopping. This review will be beneficial to the various material scientists studying the electronic properties of two-dimensional nanomaterials.
2D layered nanomaterials have attracted considerable attention for their potential for highly eff... more 2D layered nanomaterials have attracted considerable attention for their potential for highly efficient separations, among other applications. Here, a 2D lamellar membrane synthesized using hexagonal boron nitride nanoflakes (h‐BNF) for highly efficient ion separation is reported. The ion‐rejection performance and the water permeance of the membrane as a function of the ionic radius, ion valance, and solution pH are investigated. The nonfunctionalized h‐BNF membranes show excellent ion rejection for small sized salt ions as well as for anionic dyes (>97%) while maintaining a high water permeability, ≈1.0 × 10−3 L m m−2 h−1 bar−1). Experiments show that the ion‐rejection performance of the membrane can be tuned by changing the solution pH. The results also suggest that the rejection is influenced by the ionic size and the electrostatic repulsion between fixed negative charges on the BN surface and the mobile ions, and is consistent with the Donnan equilibrium model. These simple‐t...
In the last decades, the chemical engineering field has expanded and now encompasses other divers... more In the last decades, the chemical engineering field has expanded and now encompasses other diverse fields such as pharmaceutical, renewable energy, nanoparticles, food products, and safety. However, the chemical engineering curriculum has not evolved at the same pace. Thus, the gap between industry needs and competencies developed in chemical engineering (CHE) programs has grown. To adequately address this problem, the authors' goal is to synergize industry-student-academia and to enculturate classrooms with industry. Implementation of this model is particularly essential in the early years of the curriculum. As the first step, the authors aim to design and incorporate up-to-date industry problems into "Materials and Energy Balance" as a course assignment. The authors of this paper have been working with industry mentors from various areas of the chemical engineering field to design up-to-date application-based problems/projects for the selected CHE class. Five industr...
Ultrathin two dimensional (2D) metal dichalogenide (MoS 2, WS2, so forth) exhibits confinement of... more Ultrathin two dimensional (2D) metal dichalogenide (MoS 2, WS2, so forth) exhibits confinement of carriers, evolution of band structure, high on/off rectification, and high thermal absorption. However their incorporation into systems requires controlled functionalization and/or interaction with other nanoscale entities. Here, we enhance the stable sulfur/noble metal functionalization via both diffusion limited aggregation and instantaneous reaction arresting (using microwaves). These gold nanoparticles are incorporated selectively on MoS 2 crystallographic edges (with 60 0
... Authors: Kabeer Jasuja (Kansas State University). Vikas Berry (Kansas State University). In r... more ... Authors: Kabeer Jasuja (Kansas State University). Vikas Berry (Kansas State University). In recent years there has been a great interest in the architecture of 2-D sheets of graphene which have been shown to display remarkable electronic, physical and chemical properties. ...
Molecular gating (via electric field from molecule's dipole-moment) is an effective route to ... more Molecular gating (via electric field from molecule's dipole-moment) is an effective route to dope two dimensional (2D) nanomaterials for specific electronic applications. Here, we show that molybdenum disulphide (MoS2) interfaced with a microfiber of hygroscopic polyelectrolyte can be reversibly doped with water molecules by changing the local humidity. In this work, the p-doping water absorbed by the polymer microfiber reduces the electron density in the n-type MoS2 quantum dots. This change in the carrier concentration (5.24 x 10 11 cm -2 ) is confirmed by electrical measurements. Further, Raman spectra have been analyzed to understand the bonding of molecular groups on MoS2 quantum dots and their self-assembly on the microfiber. The work provides an avenue to explore interfacing 2D quantum dots interfaced with other polymers for specific sensing applications.
Abstract Boron nitride's (BN) large band gap does not permit carrier transport at ambient con... more Abstract Boron nitride's (BN) large band gap does not permit carrier transport at ambient conditions. We show that BN sheets can be exfoliated by functionalization with oxy-groups to introduce additional acceptor and donor energy levels appropriate for energy storage devices. Further, the incorporation of heteroatoms into transition metal sulfides enhances capacitance via Faradic redox reactions and their cyclic stability. The functionalized boron nitride (mK-BN) and Carbon Nanotubes (CNTs) are intertwined with a Zn-doped Cadmium-Sulfide (Zn–CdS) nanostructure to increase the surface area-charge storage. In a supercapacitor application, Zn–CdS/mK-BN/CNT exhibits a 787 F/g specific capacitance (SC) in an aqueous (aq.) electrolyte. Further, the Zn–CdS/mK-BN/CNT was deployed as a cathode material in an asymmetric supercapacitor device (ASC) coupled with an ionic electrolyte (IE), (NHEt3)+(NO3)−, offered a SC of 173 F/g with an approximate 99% stability due to the enhanced charge mobility. The reported functionalization of BN induces additional energy levels making the material ideal for energy storage devices and will directly impact the next-generation of advanced supercapacitor electrode materials.
Abstract Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alt... more Abstract Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alternatives to enhance photoabsorption, electron excitation/injection, but voltage loss remains a challenge. Here, we focus on understanding the cascading of energy levels in perovskite semiconductor cosensitized naturally-sensitized photoanodes to leverage forward charge transport addressing the voltage loss arising from ITO/TiO2 heterojunction's built-in potential. The β -carotene-sensitized TiO2 photoanode modified with methylammonium lead iodide (MAPbI3) co-sensitizer causes an upward shifting in TiO2 Fermi level (EF). This phenomenon is predominantly attributed to increased initially injected electrons due to low MAPbI3 bandgap and high visible-light absorption. Enhanced charge separation and injection mechanisms at the TiO2/MAPbI3 interface increase the effective density-of-states (DOS >2.46 × 1021 cm−3) in the TiO2 conduction band (CB) and hence decrease its work function to 4.82 eV. The decrease in TiO2 work function suppressed CB bending at ITO/TiO2 heterojunction, which minimized the photoinduced electrostatic potential barrier up to 13.1%. The reduced Schottky barrier ( φ S B H β -carotene-sensitized solar cell.
Interfacing two-dimensional graphene oxide (2D GO) platelets with one-dimensional zinc oxide nano... more Interfacing two-dimensional graphene oxide (2D GO) platelets with one-dimensional zinc oxide nanorods (1D ZnO) would create mixed-dimensional heterostructures suitable for modern optoelectronic devices. However, there remains a lack in understanding of interfacial chemistry and wettability in GO-coated-ZnO nanorod heterostructures. Here, we propose a hydroxyl-based dissociation-exchange mechanism to understand interfacial interactions responsible for GO adsorption onto ZnO nanorod hydrophobic substrates. The proposed mechanism initiated from mixing GO suspension with various organics would allow us to overcome the poor wettability (θ ~ 140.5°) of the super-hydrophobic ZnO nanorods to the drop-casted GO. The addition of different classes of organics into the relatively high pH GO suspension with a volumetric ratio of 1:3 (organic-to-GO) is believed to introduce free radicals (-OH and -COOH), which consequently result in enhancing adhesion (chemisorption) between ZnO nanorods and GO platelets. The wettability study shows as high as 75% reduction in contact angle (θ = 35.5°) when the GO suspension is mixed with alcohols (e.g. ethanol) prior to interfacing with ZnO nanorods. The interfacial chemistry developed here brings forth a scalable tool for designing graphene-coated-ZnO heterojunctions for photovoltaics, photocatalysis, biosensors, and UV detectors.
A synergistic, nanoscale electrical-interface with the membranes of exoelectrogenic microbes will... more A synergistic, nanoscale electrical-interface with the membranes of exoelectrogenic microbes will have transformative impact on biological cell based electronic-devices. In this presentation, we will report a conformal graphenic interface on biocatalytic Geobacter sulfurreducens membrane that results in quantum-capacitance induced n-doping in graphene. This further enhances electron shuttling from the membrane to improve electron harvesting from the electrogenic membrane. The quantum coupling of reduced graphene oxide (rGO) with the connected protein-membrane channels leads to an additional electron density of 3.44 x 1012 cm-2 and an increase in the in-plane phonon vibration energies (G) of rGO by 5 cm-1. This n-doping enhances the electron transfer-rate from the cell membrane into the rGO improving the power density of a simplistic microbial fuel cell (MFC) by ~ 2 folds. The synergistic electron-harvesting and conformal membrane-interfacing of flexible 2D nanomaterials can lead to ...
Designing 3D printed micro-architectures using electronic materials with well-understood electron... more Designing 3D printed micro-architectures using electronic materials with well-understood electronic transport within such structures will potentially lead to accessible device fabrication for ‘on-demand’ applications. Here we show controlled nozzle-extrusion based 3D printing of a commercially available nano-composite of graphene/polylactic acid, enabling the fabrication of a tensile gauge functioning via the readjustment of the electron-tunneling barrier width between conductive graphene-centers. The electronic transport in the graphene/polymer 3D printed structure exhibited the Fowler Nordheim mechanism with a tunneling width of 0.79–0.95 nm and graphene centers having a carrier concentration of 2.66 × 1012/cm2. Furthermore, a mechanical strain that increases the electron-tunneling width between graphene nanostructures (~ 38 nm) by only 0.19 Ǻ reduces the electron flux by 1e/s/nm2 (from 18.51 to 19.51 e/s/nm2) through the polylactic acid junctions in the 3D-printed heterostructure...
Graphene-on-semiconductor heterojunction solar cell is an emerging class of photovoltaics with po... more Graphene-on-semiconductor heterojunction solar cell is an emerging class of photovoltaics with potential for efficient and reliable energy conversion systems. The interfaces between graphene and lightly-doped semiconductor play a key role in charge-carrier separation and recombination dynamics. Owing to the low Schottky barrier height-induced interfacial charge carrier recombination, the graphene-on-silicon (Si) heterojunction solar cells suffer from instability in power conversion efficiency over time. Therefore, it is critical to engineer the interface to enhance the barrier height by interfacing a chemically-stable, insulating, and atomically-thin layer. Further, the temperature dependent photovoltaic characteristics of such stacked architectures are unknown, and temperature dependent behavior is critical to understand the MIS junction behavior and photovoltaic phenomenon. Here, we have introduced hexagonal boron nitride (h-BN) as a tunneling interlayer in graphene-on-Si heterojunction solar cells, which enables the passivation of the chemical dangling bonds on the Si surface. The effect of temperature on the performance of graphene/h-BN/Si PV cell is examined. Thin films of h-BN are directly synthesized on lightly-doped Si surface via a bottom-up chemical-surface-adsorption strategy followed by the transfer of a graphene monolayer. The 2D layer-on-2D layer-on-3D bulk semiconductor nanoarchitecture of graphene/h-BN/Si forms a metal-insulator-semiconductor (MIS)-type junction, where the h-BN acts as an electron-blocking layer to avoid interfacial charge carrier recombination. A 4-fold increase in open-circuit voltage (VOC) is found for graphene/h-BN/Si heterojunction cell (0.52 V) in contrast to the graphene/Si cell (0.13 V), which is due to the increase in the Schottky barrier height and hence built-in electric potential. Interestingly, the VOC linearly decreases by only ~4% with every 10 K increase in temperature. This work will lead to an evolution of new 2D/2D/3D nanoarchitectures for mechanically-robust, high performance, and durable optoelectronic functionalities.
Leveraging the phononic sensitivity and scalability of nano‐biointerfaces has accelerated the gro... more Leveraging the phononic sensitivity and scalability of nano‐biointerfaces has accelerated the growth of unique and versatile biosensors. Graphene has the properties of a near‐ideal signal transducer, due to the strong coupling between its interfacial and phononic properties. This enables sensitive yet quick detection of surface interactions on graphene via Raman spectral analysis. The Raman‐active vibrational bands of graphene are demonstrated to be sensitive to structural, electrical, and interfacial modifications. This sensitivity is attributed to graphene's electron–phonon coupling and high quantum capacitance. The fundamental understanding of graphene phonons is crucial for developing reliable platforms for disease and infectious agent detection. This review provides a mechanistic explanation of these phenomena at the interface between graphene and various biosystems (including cancerous, bacterial, viral, and biophysical specimens) to set the foundation for next‐generation ...
Abstract The realization of unique scientific phenomena in two-dimensional nanomaterials (2DNMs) ... more Abstract The realization of unique scientific phenomena in two-dimensional nanomaterials (2DNMs) has led to their applications in several electronic fields; making it imperative to understand the conduction mechanism of charge carriers in such systems. Though several studies have been conducted on 2DNMs with pristine crystallinity, the inevitable presence of defects in the crystals requires careful consideration of their effect on 2DNMs’ electrical behavior. Here, we outline the effects of chemical, structural, substrate-induced defects and disorder on the conduction mechanism within 2DNMs, particularly graphene derivatives and MoS2. The conduction mechanisms discussed in this work are thermally activated conduction, nearest neighbor hopping, Efros-Shklovskii variable range hopping, and Mott variable range hopping. This review will be beneficial to the various material scientists studying the electronic properties of two-dimensional nanomaterials.
2D layered nanomaterials have attracted considerable attention for their potential for highly eff... more 2D layered nanomaterials have attracted considerable attention for their potential for highly efficient separations, among other applications. Here, a 2D lamellar membrane synthesized using hexagonal boron nitride nanoflakes (h‐BNF) for highly efficient ion separation is reported. The ion‐rejection performance and the water permeance of the membrane as a function of the ionic radius, ion valance, and solution pH are investigated. The nonfunctionalized h‐BNF membranes show excellent ion rejection for small sized salt ions as well as for anionic dyes (>97%) while maintaining a high water permeability, ≈1.0 × 10−3 L m m−2 h−1 bar−1). Experiments show that the ion‐rejection performance of the membrane can be tuned by changing the solution pH. The results also suggest that the rejection is influenced by the ionic size and the electrostatic repulsion between fixed negative charges on the BN surface and the mobile ions, and is consistent with the Donnan equilibrium model. These simple‐t...
In the last decades, the chemical engineering field has expanded and now encompasses other divers... more In the last decades, the chemical engineering field has expanded and now encompasses other diverse fields such as pharmaceutical, renewable energy, nanoparticles, food products, and safety. However, the chemical engineering curriculum has not evolved at the same pace. Thus, the gap between industry needs and competencies developed in chemical engineering (CHE) programs has grown. To adequately address this problem, the authors' goal is to synergize industry-student-academia and to enculturate classrooms with industry. Implementation of this model is particularly essential in the early years of the curriculum. As the first step, the authors aim to design and incorporate up-to-date industry problems into "Materials and Energy Balance" as a course assignment. The authors of this paper have been working with industry mentors from various areas of the chemical engineering field to design up-to-date application-based problems/projects for the selected CHE class. Five industr...
Ultrathin two dimensional (2D) metal dichalogenide (MoS 2, WS2, so forth) exhibits confinement of... more Ultrathin two dimensional (2D) metal dichalogenide (MoS 2, WS2, so forth) exhibits confinement of carriers, evolution of band structure, high on/off rectification, and high thermal absorption. However their incorporation into systems requires controlled functionalization and/or interaction with other nanoscale entities. Here, we enhance the stable sulfur/noble metal functionalization via both diffusion limited aggregation and instantaneous reaction arresting (using microwaves). These gold nanoparticles are incorporated selectively on MoS 2 crystallographic edges (with 60 0
... Authors: Kabeer Jasuja (Kansas State University). Vikas Berry (Kansas State University). In r... more ... Authors: Kabeer Jasuja (Kansas State University). Vikas Berry (Kansas State University). In recent years there has been a great interest in the architecture of 2-D sheets of graphene which have been shown to display remarkable electronic, physical and chemical properties. ...
Molecular gating (via electric field from molecule's dipole-moment) is an effective route to ... more Molecular gating (via electric field from molecule's dipole-moment) is an effective route to dope two dimensional (2D) nanomaterials for specific electronic applications. Here, we show that molybdenum disulphide (MoS2) interfaced with a microfiber of hygroscopic polyelectrolyte can be reversibly doped with water molecules by changing the local humidity. In this work, the p-doping water absorbed by the polymer microfiber reduces the electron density in the n-type MoS2 quantum dots. This change in the carrier concentration (5.24 x 10 11 cm -2 ) is confirmed by electrical measurements. Further, Raman spectra have been analyzed to understand the bonding of molecular groups on MoS2 quantum dots and their self-assembly on the microfiber. The work provides an avenue to explore interfacing 2D quantum dots interfaced with other polymers for specific sensing applications.
Abstract Boron nitride's (BN) large band gap does not permit carrier transport at ambient con... more Abstract Boron nitride's (BN) large band gap does not permit carrier transport at ambient conditions. We show that BN sheets can be exfoliated by functionalization with oxy-groups to introduce additional acceptor and donor energy levels appropriate for energy storage devices. Further, the incorporation of heteroatoms into transition metal sulfides enhances capacitance via Faradic redox reactions and their cyclic stability. The functionalized boron nitride (mK-BN) and Carbon Nanotubes (CNTs) are intertwined with a Zn-doped Cadmium-Sulfide (Zn–CdS) nanostructure to increase the surface area-charge storage. In a supercapacitor application, Zn–CdS/mK-BN/CNT exhibits a 787 F/g specific capacitance (SC) in an aqueous (aq.) electrolyte. Further, the Zn–CdS/mK-BN/CNT was deployed as a cathode material in an asymmetric supercapacitor device (ASC) coupled with an ionic electrolyte (IE), (NHEt3)+(NO3)−, offered a SC of 173 F/g with an approximate 99% stability due to the enhanced charge mobility. The reported functionalization of BN induces additional energy levels making the material ideal for energy storage devices and will directly impact the next-generation of advanced supercapacitor electrode materials.
Abstract Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alt... more Abstract Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alternatives to enhance photoabsorption, electron excitation/injection, but voltage loss remains a challenge. Here, we focus on understanding the cascading of energy levels in perovskite semiconductor cosensitized naturally-sensitized photoanodes to leverage forward charge transport addressing the voltage loss arising from ITO/TiO2 heterojunction's built-in potential. The β -carotene-sensitized TiO2 photoanode modified with methylammonium lead iodide (MAPbI3) co-sensitizer causes an upward shifting in TiO2 Fermi level (EF). This phenomenon is predominantly attributed to increased initially injected electrons due to low MAPbI3 bandgap and high visible-light absorption. Enhanced charge separation and injection mechanisms at the TiO2/MAPbI3 interface increase the effective density-of-states (DOS >2.46 × 1021 cm−3) in the TiO2 conduction band (CB) and hence decrease its work function to 4.82 eV. The decrease in TiO2 work function suppressed CB bending at ITO/TiO2 heterojunction, which minimized the photoinduced electrostatic potential barrier up to 13.1%. The reduced Schottky barrier ( φ S B H β -carotene-sensitized solar cell.
Interfacing two-dimensional graphene oxide (2D GO) platelets with one-dimensional zinc oxide nano... more Interfacing two-dimensional graphene oxide (2D GO) platelets with one-dimensional zinc oxide nanorods (1D ZnO) would create mixed-dimensional heterostructures suitable for modern optoelectronic devices. However, there remains a lack in understanding of interfacial chemistry and wettability in GO-coated-ZnO nanorod heterostructures. Here, we propose a hydroxyl-based dissociation-exchange mechanism to understand interfacial interactions responsible for GO adsorption onto ZnO nanorod hydrophobic substrates. The proposed mechanism initiated from mixing GO suspension with various organics would allow us to overcome the poor wettability (θ ~ 140.5°) of the super-hydrophobic ZnO nanorods to the drop-casted GO. The addition of different classes of organics into the relatively high pH GO suspension with a volumetric ratio of 1:3 (organic-to-GO) is believed to introduce free radicals (-OH and -COOH), which consequently result in enhancing adhesion (chemisorption) between ZnO nanorods and GO platelets. The wettability study shows as high as 75% reduction in contact angle (θ = 35.5°) when the GO suspension is mixed with alcohols (e.g. ethanol) prior to interfacing with ZnO nanorods. The interfacial chemistry developed here brings forth a scalable tool for designing graphene-coated-ZnO heterojunctions for photovoltaics, photocatalysis, biosensors, and UV detectors.
A synergistic, nanoscale electrical-interface with the membranes of exoelectrogenic microbes will... more A synergistic, nanoscale electrical-interface with the membranes of exoelectrogenic microbes will have transformative impact on biological cell based electronic-devices. In this presentation, we will report a conformal graphenic interface on biocatalytic Geobacter sulfurreducens membrane that results in quantum-capacitance induced n-doping in graphene. This further enhances electron shuttling from the membrane to improve electron harvesting from the electrogenic membrane. The quantum coupling of reduced graphene oxide (rGO) with the connected protein-membrane channels leads to an additional electron density of 3.44 x 1012 cm-2 and an increase in the in-plane phonon vibration energies (G) of rGO by 5 cm-1. This n-doping enhances the electron transfer-rate from the cell membrane into the rGO improving the power density of a simplistic microbial fuel cell (MFC) by ~ 2 folds. The synergistic electron-harvesting and conformal membrane-interfacing of flexible 2D nanomaterials can lead to ...
Designing 3D printed micro-architectures using electronic materials with well-understood electron... more Designing 3D printed micro-architectures using electronic materials with well-understood electronic transport within such structures will potentially lead to accessible device fabrication for ‘on-demand’ applications. Here we show controlled nozzle-extrusion based 3D printing of a commercially available nano-composite of graphene/polylactic acid, enabling the fabrication of a tensile gauge functioning via the readjustment of the electron-tunneling barrier width between conductive graphene-centers. The electronic transport in the graphene/polymer 3D printed structure exhibited the Fowler Nordheim mechanism with a tunneling width of 0.79–0.95 nm and graphene centers having a carrier concentration of 2.66 × 1012/cm2. Furthermore, a mechanical strain that increases the electron-tunneling width between graphene nanostructures (~ 38 nm) by only 0.19 Ǻ reduces the electron flux by 1e/s/nm2 (from 18.51 to 19.51 e/s/nm2) through the polylactic acid junctions in the 3D-printed heterostructure...
Graphene-on-semiconductor heterojunction solar cell is an emerging class of photovoltaics with po... more Graphene-on-semiconductor heterojunction solar cell is an emerging class of photovoltaics with potential for efficient and reliable energy conversion systems. The interfaces between graphene and lightly-doped semiconductor play a key role in charge-carrier separation and recombination dynamics. Owing to the low Schottky barrier height-induced interfacial charge carrier recombination, the graphene-on-silicon (Si) heterojunction solar cells suffer from instability in power conversion efficiency over time. Therefore, it is critical to engineer the interface to enhance the barrier height by interfacing a chemically-stable, insulating, and atomically-thin layer. Further, the temperature dependent photovoltaic characteristics of such stacked architectures are unknown, and temperature dependent behavior is critical to understand the MIS junction behavior and photovoltaic phenomenon. Here, we have introduced hexagonal boron nitride (h-BN) as a tunneling interlayer in graphene-on-Si heterojunction solar cells, which enables the passivation of the chemical dangling bonds on the Si surface. The effect of temperature on the performance of graphene/h-BN/Si PV cell is examined. Thin films of h-BN are directly synthesized on lightly-doped Si surface via a bottom-up chemical-surface-adsorption strategy followed by the transfer of a graphene monolayer. The 2D layer-on-2D layer-on-3D bulk semiconductor nanoarchitecture of graphene/h-BN/Si forms a metal-insulator-semiconductor (MIS)-type junction, where the h-BN acts as an electron-blocking layer to avoid interfacial charge carrier recombination. A 4-fold increase in open-circuit voltage (VOC) is found for graphene/h-BN/Si heterojunction cell (0.52 V) in contrast to the graphene/Si cell (0.13 V), which is due to the increase in the Schottky barrier height and hence built-in electric potential. Interestingly, the VOC linearly decreases by only ~4% with every 10 K increase in temperature. This work will lead to an evolution of new 2D/2D/3D nanoarchitectures for mechanically-robust, high performance, and durable optoelectronic functionalities.
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