Yousheng Wang - Academia.edu (original) (raw)

Papers by Yousheng Wang

Research paper thumbnail of Hole-Transport Management Enables 23%-Efficient and Stable Inverted Perovskite Solar Cells with 84% Fill Factor

Nano-Micro Letters

NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost,... more NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs prese...

Research paper thumbnail of Best Poster Award--12th International Conference on Ceramic Materials and Components for Energy and Environmental Applications (CMCEE 2018) in Singapore

Research paper thumbnail of Highly Efficient Non-Enzymatic Glucose Sensor Based on CuO Modified Vertically-Grown ZnO Nanorods on Electrode

Scientific reports, Jan 18, 2017

There is a major challenge to attach nanostructures on to the electrode surface while retaining t... more There is a major challenge to attach nanostructures on to the electrode surface while retaining their engineered morphology, high surface area, physiochemical features for promising sensing applications. In this study, we have grown vertically-aligned ZnO nanorods (NRs) on fluorine doped tin oxide (FTO) electrodes and decorated with CuO to achieve high-performance non-enzymatic glucose sensor. This unique CuO-ZnO NRs hybrid provides large surface area and an easy substrate penetrable structure facilitating enhanced electrochemical features towards glucose oxidation. As a result, fabricated electrodes exhibit high sensitivity (2961.7 μA mM(-1) cm(-2)), linear range up to 8.45 mM, low limit of detection (0.40 μM), and short response time (<2 s), along with excellent reproducibility, repeatability, stability, selectivity, and applicability for glucose detection in human serum samples. Circumventing, the outstanding performance originating from CuO modified ZnO NRs acts as an efficie...

Research paper thumbnail of Recent progress in perovskite solar cells: material science

Research paper thumbnail of Sno2/Basno3 Electron Transport Materials for Stable and Efficient Perovskite Solar Cells

Research paper thumbnail of Green Antisolvent-Mediators Stabilize Perovskites for Efficient Niox-Based Inverted Solar Cells with Voc Approaching 1.2 V

Research paper thumbnail of Multifunctional Two-Dimensional Benzodifuran-Based Polymer for Eco-Friendly Perovskite Solar Cells Featuring High Stability

ACS Applied Materials & Interfaces

Research paper thumbnail of Interfacial engineering with carbon–graphite–CuδNi1−δO for ambient-air stable composite-based hole-conductor-free perovskite solar cells

Nanoscale Advances, 2020

Fully-ambient-air processed HCF-PSCs based on carbon–graphite–CuδNi1−δO composites show not only ... more Fully-ambient-air processed HCF-PSCs based on carbon–graphite–CuδNi1−δO composites show not only efficient performance but also remarkably improved photo-, thermal-stability and long-term air stability.

Research paper thumbnail of Natural methionine-passivated MAPbI3 perovskite films for efficient and stable solar devices

Advanced Composites and Hybrid Materials, 2021

Defects located at the surfaces and grain boundaries of solution-processed perovskite films serve... more Defects located at the surfaces and grain boundaries of solution-processed perovskite films serve as nonradiative recombination centers and are detrimental for the photovoltaic performance of solar devices. Herein, a natural amino acid molecule methionine (Met) is selected as an effective passivation agent to enhance the optoelectronic properties of methylammonium lead iodide (MAPbI3) films. The incorporation of a small amount of Met significantly reduces the trap-state density, contributing to longer carrier lifetime of the perovskite films. As a result, solar cells made of Met-mediated perovskite films deliver a high photovoltage of 1.145 V, which is up to 100 mV higher than the control device. In addition, the Met-mediated device exhibits enhanced stability due to the reduced trap states and the improved hydrophobic property of the modified perovskite film, which retains ~ 85% of their initial efficiency after 480-h storage. The effective methionine passivation is reported, which significantly reduces the trap-state density and leads to longer carrier lifetime of the perovskite films. Methionine-mediated device produces a champion efficiency of 20.13%, with enhanced moisture stability.

Research paper thumbnail of Cation-size mismatch and interface stabilization for efficient NiOx-based inverted perovskite solar cells with 21.9% efficiency

Nano Energy, 2021

Abstract Stabilization of perovskite phases and interfaces in stacked perovskite photovoltaics ar... more Abstract Stabilization of perovskite phases and interfaces in stacked perovskite photovoltaics are critical for their efficiency, operational stability and perovskite solar modules (PSMs). Herein, A-site cation-size mismatch processed perovskite-composition films with less crystal defects are formed by incorporating larger cations formamidinium and methylammonium with smaller cations, i.e., potassium and cesium. The interface stabilization can be achieved by inserting Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine], mesoporous alumina, phenethyammonium ligands and atomic-layer-deposition tin oxides at desired interfaces in inverted perovskite solar cells (PSCs). Thus, the interface defects, non-radiative recombination and ion migration can be remarkably suppressed, resulting in improvement of interface contacts and hole/electron transport. As a result, both cation-size mismatch and interface stabilization (CM-IS) strategies enable hysteresis-free, reproducible 21.9% and 16.9% efficient NiOx-based inverted PSCs and PSMs. Moreover, a high Voc of 1.16 V and 8.05 V can be obtained in large-area PSCs (1 cm2) and PSMs (11.2 cm2) with 7 subcells connected in series. Additionally, the measured T85 lifetime (the time as a function of PCEs decrease to 85% of its initial value) of unencapsulated PSCs under continuous AM 1.5G light illumination is approximately 1000 h.

Research paper thumbnail of Fully-ambient-air and antisolvent-free-processed stable perovskite solar cells with perovskite-based composites and interface engineering

Nano Energy, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of High response and low concentration hydrogen gas sensing properties using hollow ZnO particles transformed from polystyrene@ZnO core-shell structures

International Journal of Hydrogen Energy, 2019

High quality, closely packed nanorods (NRs) textured ZnO hollow particles were prepared via therm... more High quality, closely packed nanorods (NRs) textured ZnO hollow particles were prepared via thermal treatment of polystyrene@ZnO core-shell structures at 300 C. Polystyrene@ZnO core-shell structures were synthesized using a chemical route. These hollow ZnO particles were investigated for hydrogen gas sensing properties. Morphological properties were studied using field emission scanning electron microscope (FE-SEM). Structural parameters and molecular fingerprint confirmation were carried out by x-ray diffraction (XRD) and Raman analysis respectively. The elemental compositions and atomic species of sensor materials were studied using energy dispersive spectrometer (EDS) analysis and x-ray photoelectron spectroscopy (XPS) spectra respectively. The study of atomic planar arrangements and crystalline nature were examined by using a highresolution transmission electron microscope (HR-TEM) micrograph and selected area electron diffraction (SAED) pattern respectively. Hollow ZnO particles sensor was revealed remarkable selectivity towards hydrogen (H 2) gas. The lowest H 2 detection limit of ZnO sensor was at 2 ppm with the response of 7%, whereas 89% gas response was recorded for 100 ppm at optimized temperature 225 C with response time 139 s. Gas response as a function of operating temperatures as well as gas concentrations was tested along with good sensor stability. The transient gas response and selectivity studies were carried out and analyzed. ZnO growth and gas sensing mechanisms were elucidated.

Research paper thumbnail of Nozzle-Jet-Printed Silver/Graphene Composite-Based Field-Effect Transistor Sensor for Phosphate Ion Detection

ACS Omega, 2019

High concentration of dissolved phosphate ions is the main responsible factor for eutrophication ... more High concentration of dissolved phosphate ions is the main responsible factor for eutrophication of natural water bodies. Therefore, detection of phosphate ions is essential for evaluating water eutrophication. There is a need at large-scale production of real-time monitoring technology to detect phosphorus accurately. In this study, facile enzymeless phosphate ion detection is reported using a nozzle-jet-printed silver/reduced graphene oxide (Ag/rGO) composite-based field-effect transistor sensor on flexible and disposable polymer substrates. The sensor exhibits promising results in low concentration as well as real-time phosphate ion detection. The sensor shows excellent performance with a wide linear range of 0.005−6.00 mM, high sensitivity of 62.2 μA/ cm 2 /mM, and low detection limit of 0.2 μM. This facile combined technology readily facilitates the phosphate ion detection with high performance, long-term stability, excellent reproducibility, and good selectivity in the presence of other interfering anions. The sensor fabrication method and phosphate detection technique yield low-cost, user-friendly sensing devices with less analyte consumption, which are easy to fabricate on polymer substrates on a large scale. Besides, the sensor has the capability to sense phosphate ions in real water samples, which makes it applicable in environmental monitoring.

Research paper thumbnail of Cost-effective silver ink for printable and flexible electronics with robust mechanical performance

Chemical Engineering Journal, 2019

An ideal silver precursor ink should be highly stable, transparent, and compatible with a broad r... more An ideal silver precursor ink should be highly stable, transparent, and compatible with a broad range of substrates and facile fabricating techniques to provide a uniform electrodes with bulk conductivity at mild temperatures (<100 °C) for high performance electronic applications. Herein, we report a facile chemical route to develop the robust silver precursor ink having long stability, which possesses key characteristics of an optimal ink and provides a practical realization in flexible electronics via multiple techniques. The obtained transparent silver ink offers an unambiguously unique and economical approach towards printable electronic devices. The silver electrodes are fabricated by silver ink nozzle-jet printing and ink-pen writing that demonstrate remarkable conductivities (10 6-10 7 S/m) close to bulk silver (~10 7 S/m) after annealing at 70-100 °C. The adhesion and conductivity of printed silver is highly stable in various mechanical bending. High quality nano-crystalline and pin holes free silver patterns are observed on flexible PET and PI substrates. The probable mechanism for formulated silver ink is elucidated. The precursor ink formulation process can possibly eliminate the need for costlier methods such as gravure printing and paves the way to industrial manufacturing of prudent electronic devices.

Research paper thumbnail of Fully-ambient-processed mesoscopic semitransparent perovskite solar cells by islands-structure-MAPbI3-xClx-NiO composite and Al2O3/NiO interface engineering

Nano Energy, 2018

Perovskite solar cells (PSCs) because of low-cost fabrication and high performance have shown sup... more Perovskite solar cells (PSCs) because of low-cost fabrication and high performance have shown superb potential for the next-generation photovoltaic application. For the potential applications of photovoltaic technologies, semitransparent PSCs are also highly attractive and of commercial interest to develop building-and tandem-integrated solar cells. Here, we present fully-ambientprocessed stable and mesoscopic semitransparent PSCs by non-continuous islands-structure-CH 3 NH 3 PbI 3-x Cl x-NiO nanoparticles (MAPbI 3-x Cl x-NiO NPs) composite and interface engineering by inserting Al 2 O 3 /NiO between TiO 2 and MAPbI 3-x Cl x-NiO composite layers in a device configuration of FTO/c-TiO 2 /mp-TiO 2 /Al 2 O 3 /NiO/islands-structure-MAPbI 3-x Cl x-NiO /spiro-OMeTAD/Au. Except for the islands-structure-MAPbI 3-x Cl x-NiO capping layer, a uniform and thicker and transparent TiO 2 /Al 2 O 3 /NiO/MAPbI 3-x Cl x composite layer is formed, which can effectively reduce photocurrent density loss and interface recombination. Interestingly, the optimized semitransparent PSCs showed hysteresis-free performance. The average visible transmittance (AVT) of MAPbI 3-x Cl x-NiO NPs composite film was ranged from 18% to 56% and the corresponding device PCE changed from 17.51% to 12.47%. The PSCs without encapsulation showed an excellent air stability over 270 days with retaining ~98% of its original V oc , ~96% of J sc , ~97% of FF and ~93% of PCE under ambient condition (25-30℃ and 45-50 % humidity). Finally, we achieved semitransparent device of PCE = 10.

Research paper thumbnail of Graphene and its derivatives for solar cells application

Nano Energy, 2018

Graphene has played the role of game-changer for conductive transparent devices indebted to its u... more Graphene has played the role of game-changer for conductive transparent devices indebted to its unique two dimensional (2D) structures and gained an exceptional opportunity to be employed in energy industry. In the past two decades graphene has been merged with the concept of photovoltaic (PV) material and exhibited a significant role as a transparent electrode, hole/electron transport material and interfacial buffer layer in solar cell devices. This review covers the different methods of graphene fabrication and broadly discusses the recent advances in graphene-based solar cells, including bulk heterojunction (BHJ) organic, dye-sensitized and perovskite solar cell deices. The power conversion efficiency surpassed 20.3 % for graphene-based perovskite solar cells and hit the efficiency of 10 % for BHJ organic solar cells. Except the part of charge extracting and transport to the electrodes, graphene has another unique role of device protection against environmental degradation via its packed 2D network structure and provides long-term environmental stability for PV devices. We highlighted a comparative study on the role of graphene and its derivatives in photovoltaic devices. After all, the potential issues and the perspective for future research in graphene-based materials for PV applications are presented.

Research paper thumbnail of Efficient bulk heterojunction hybrid solar cells with graphene-silver nanoparticles composite synthesized by microwave-assisted reduction

Nano Energy, 2016

Herein, we present a simple, eco-friendly one-step microwave-assisted reduction (MWAR) that can p... more Herein, we present a simple, eco-friendly one-step microwave-assisted reduction (MWAR) that can produce silver nanoparticles (Ag NPs) and reduced graphene oxide (rGO) in the form of Ag-rGO composites for application in heterojunction hybrid solar cells. The field-effect transistor fabricated with the MWAR Ag-rGO composite showed p-type behavior with a high mobility of 3.3x10 5 cm 2 V-1 s-1 and conductivity of 9x10 6 S/m which is one-order of magnitude greater than pristine graphene (i.e., 1.59x10 5 S/m). As-synthesized Ag-rGO composite was introduced into the active layer of bulk heterojunction solar cell based on P3HT:PCBM. Compared to the P3HT:PCBM only device (i.e., control device), the Ag-rGO implemented device showed a power conversion efficiency (PCE) of 4.23 %, which is about 42 % increase over the control device (i.e. PCE=2.98 %). This dramatic increase in PCE was found to be mainly due to an increase in short-circuit current (J sc) from 9.55 to 12.76 mA/cm 2 (about 33 % increase), suggesting that the incorporation of p-type Ag-rGO into the active layer enhances the charge carrier generation and fast extraction of holes to the electrode. Furthermore, the Ag-rGO composite based solar cells without encapsulation showed remarkable air stability with retaining ~90 % of its original PCE and ~93% of J sc for 30 days under ambient environment, attributed to gas barrier feature of the randomly distributed graphene sheets.

Research paper thumbnail of Ambient-air-solution-processed efficient and highly stable perovskite solar cells based on CH3NH3PbI3−xClx-NiO composite with Al2O3/NiO interfacial engineering

Nano Energy, 2017

The poor air-stability and reproducibility of perovskite solar cells (PSCs) have prevented the pr... more The poor air-stability and reproducibility of perovskite solar cells (PSCs) have prevented the practical applications of the devices that can withstand sustained operation under ambient air conditions. Here, we report all-ambient-air-solution-processed PSCs based on CH 3 NH 3 PbI 3-x Cl x-NiO composite film with inserting Al 2 O 3 /NiO at the TiO 2 /perovskite interface in a cell configuration of FTO/c-TiO 2 /mp-TiO 2 /Al 2 O 3 /NiO/MAPbI 3-x Cl x-NiO/spiro-OMeTAD/Au. The interface engineering with Al 2 O 3 /NiO not only improves crystalline quality of perovskite films and enhances charge transport, but also effectively suppresses carrier recombination. This composite-based interface engineering PSCs showed a high power conversion efficiency (PCE) of 18.14 % and excellent reproducibility with average 16-18 % PCE for 35 devices. More importantly, the devices without encapsulation showed a significant enhancement in long-term air-stability; the device photovoltaic parameters stabilized after 20 days and sustained its stability over 210 days with retaining ~100% of its original V oc , ~94% of J sc , ~91% of FF and ~86% of PCE in an ambient environment.

Research paper thumbnail of Hole-Transport Management Enables 23%-Efficient and Stable Inverted Perovskite Solar Cells with 84% Fill Factor

Nano-Micro Letters

NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost,... more NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs prese...

Research paper thumbnail of Best Poster Award--12th International Conference on Ceramic Materials and Components for Energy and Environmental Applications (CMCEE 2018) in Singapore

Research paper thumbnail of Highly Efficient Non-Enzymatic Glucose Sensor Based on CuO Modified Vertically-Grown ZnO Nanorods on Electrode

Scientific reports, Jan 18, 2017

There is a major challenge to attach nanostructures on to the electrode surface while retaining t... more There is a major challenge to attach nanostructures on to the electrode surface while retaining their engineered morphology, high surface area, physiochemical features for promising sensing applications. In this study, we have grown vertically-aligned ZnO nanorods (NRs) on fluorine doped tin oxide (FTO) electrodes and decorated with CuO to achieve high-performance non-enzymatic glucose sensor. This unique CuO-ZnO NRs hybrid provides large surface area and an easy substrate penetrable structure facilitating enhanced electrochemical features towards glucose oxidation. As a result, fabricated electrodes exhibit high sensitivity (2961.7 μA mM(-1) cm(-2)), linear range up to 8.45 mM, low limit of detection (0.40 μM), and short response time (<2 s), along with excellent reproducibility, repeatability, stability, selectivity, and applicability for glucose detection in human serum samples. Circumventing, the outstanding performance originating from CuO modified ZnO NRs acts as an efficie...

Research paper thumbnail of Recent progress in perovskite solar cells: material science

Research paper thumbnail of Sno2/Basno3 Electron Transport Materials for Stable and Efficient Perovskite Solar Cells

Research paper thumbnail of Green Antisolvent-Mediators Stabilize Perovskites for Efficient Niox-Based Inverted Solar Cells with Voc Approaching 1.2 V

Research paper thumbnail of Multifunctional Two-Dimensional Benzodifuran-Based Polymer for Eco-Friendly Perovskite Solar Cells Featuring High Stability

ACS Applied Materials & Interfaces

Research paper thumbnail of Interfacial engineering with carbon–graphite–CuδNi1−δO for ambient-air stable composite-based hole-conductor-free perovskite solar cells

Nanoscale Advances, 2020

Fully-ambient-air processed HCF-PSCs based on carbon–graphite–CuδNi1−δO composites show not only ... more Fully-ambient-air processed HCF-PSCs based on carbon–graphite–CuδNi1−δO composites show not only efficient performance but also remarkably improved photo-, thermal-stability and long-term air stability.

Research paper thumbnail of Natural methionine-passivated MAPbI3 perovskite films for efficient and stable solar devices

Advanced Composites and Hybrid Materials, 2021

Defects located at the surfaces and grain boundaries of solution-processed perovskite films serve... more Defects located at the surfaces and grain boundaries of solution-processed perovskite films serve as nonradiative recombination centers and are detrimental for the photovoltaic performance of solar devices. Herein, a natural amino acid molecule methionine (Met) is selected as an effective passivation agent to enhance the optoelectronic properties of methylammonium lead iodide (MAPbI3) films. The incorporation of a small amount of Met significantly reduces the trap-state density, contributing to longer carrier lifetime of the perovskite films. As a result, solar cells made of Met-mediated perovskite films deliver a high photovoltage of 1.145 V, which is up to 100 mV higher than the control device. In addition, the Met-mediated device exhibits enhanced stability due to the reduced trap states and the improved hydrophobic property of the modified perovskite film, which retains ~ 85% of their initial efficiency after 480-h storage. The effective methionine passivation is reported, which significantly reduces the trap-state density and leads to longer carrier lifetime of the perovskite films. Methionine-mediated device produces a champion efficiency of 20.13%, with enhanced moisture stability.

Research paper thumbnail of Cation-size mismatch and interface stabilization for efficient NiOx-based inverted perovskite solar cells with 21.9% efficiency

Nano Energy, 2021

Abstract Stabilization of perovskite phases and interfaces in stacked perovskite photovoltaics ar... more Abstract Stabilization of perovskite phases and interfaces in stacked perovskite photovoltaics are critical for their efficiency, operational stability and perovskite solar modules (PSMs). Herein, A-site cation-size mismatch processed perovskite-composition films with less crystal defects are formed by incorporating larger cations formamidinium and methylammonium with smaller cations, i.e., potassium and cesium. The interface stabilization can be achieved by inserting Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine], mesoporous alumina, phenethyammonium ligands and atomic-layer-deposition tin oxides at desired interfaces in inverted perovskite solar cells (PSCs). Thus, the interface defects, non-radiative recombination and ion migration can be remarkably suppressed, resulting in improvement of interface contacts and hole/electron transport. As a result, both cation-size mismatch and interface stabilization (CM-IS) strategies enable hysteresis-free, reproducible 21.9% and 16.9% efficient NiOx-based inverted PSCs and PSMs. Moreover, a high Voc of 1.16 V and 8.05 V can be obtained in large-area PSCs (1 cm2) and PSMs (11.2 cm2) with 7 subcells connected in series. Additionally, the measured T85 lifetime (the time as a function of PCEs decrease to 85% of its initial value) of unencapsulated PSCs under continuous AM 1.5G light illumination is approximately 1000 h.

Research paper thumbnail of Fully-ambient-air and antisolvent-free-processed stable perovskite solar cells with perovskite-based composites and interface engineering

Nano Energy, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of High response and low concentration hydrogen gas sensing properties using hollow ZnO particles transformed from polystyrene@ZnO core-shell structures

International Journal of Hydrogen Energy, 2019

High quality, closely packed nanorods (NRs) textured ZnO hollow particles were prepared via therm... more High quality, closely packed nanorods (NRs) textured ZnO hollow particles were prepared via thermal treatment of polystyrene@ZnO core-shell structures at 300 C. Polystyrene@ZnO core-shell structures were synthesized using a chemical route. These hollow ZnO particles were investigated for hydrogen gas sensing properties. Morphological properties were studied using field emission scanning electron microscope (FE-SEM). Structural parameters and molecular fingerprint confirmation were carried out by x-ray diffraction (XRD) and Raman analysis respectively. The elemental compositions and atomic species of sensor materials were studied using energy dispersive spectrometer (EDS) analysis and x-ray photoelectron spectroscopy (XPS) spectra respectively. The study of atomic planar arrangements and crystalline nature were examined by using a highresolution transmission electron microscope (HR-TEM) micrograph and selected area electron diffraction (SAED) pattern respectively. Hollow ZnO particles sensor was revealed remarkable selectivity towards hydrogen (H 2) gas. The lowest H 2 detection limit of ZnO sensor was at 2 ppm with the response of 7%, whereas 89% gas response was recorded for 100 ppm at optimized temperature 225 C with response time 139 s. Gas response as a function of operating temperatures as well as gas concentrations was tested along with good sensor stability. The transient gas response and selectivity studies were carried out and analyzed. ZnO growth and gas sensing mechanisms were elucidated.

Research paper thumbnail of Nozzle-Jet-Printed Silver/Graphene Composite-Based Field-Effect Transistor Sensor for Phosphate Ion Detection

ACS Omega, 2019

High concentration of dissolved phosphate ions is the main responsible factor for eutrophication ... more High concentration of dissolved phosphate ions is the main responsible factor for eutrophication of natural water bodies. Therefore, detection of phosphate ions is essential for evaluating water eutrophication. There is a need at large-scale production of real-time monitoring technology to detect phosphorus accurately. In this study, facile enzymeless phosphate ion detection is reported using a nozzle-jet-printed silver/reduced graphene oxide (Ag/rGO) composite-based field-effect transistor sensor on flexible and disposable polymer substrates. The sensor exhibits promising results in low concentration as well as real-time phosphate ion detection. The sensor shows excellent performance with a wide linear range of 0.005−6.00 mM, high sensitivity of 62.2 μA/ cm 2 /mM, and low detection limit of 0.2 μM. This facile combined technology readily facilitates the phosphate ion detection with high performance, long-term stability, excellent reproducibility, and good selectivity in the presence of other interfering anions. The sensor fabrication method and phosphate detection technique yield low-cost, user-friendly sensing devices with less analyte consumption, which are easy to fabricate on polymer substrates on a large scale. Besides, the sensor has the capability to sense phosphate ions in real water samples, which makes it applicable in environmental monitoring.

Research paper thumbnail of Cost-effective silver ink for printable and flexible electronics with robust mechanical performance

Chemical Engineering Journal, 2019

An ideal silver precursor ink should be highly stable, transparent, and compatible with a broad r... more An ideal silver precursor ink should be highly stable, transparent, and compatible with a broad range of substrates and facile fabricating techniques to provide a uniform electrodes with bulk conductivity at mild temperatures (<100 °C) for high performance electronic applications. Herein, we report a facile chemical route to develop the robust silver precursor ink having long stability, which possesses key characteristics of an optimal ink and provides a practical realization in flexible electronics via multiple techniques. The obtained transparent silver ink offers an unambiguously unique and economical approach towards printable electronic devices. The silver electrodes are fabricated by silver ink nozzle-jet printing and ink-pen writing that demonstrate remarkable conductivities (10 6-10 7 S/m) close to bulk silver (~10 7 S/m) after annealing at 70-100 °C. The adhesion and conductivity of printed silver is highly stable in various mechanical bending. High quality nano-crystalline and pin holes free silver patterns are observed on flexible PET and PI substrates. The probable mechanism for formulated silver ink is elucidated. The precursor ink formulation process can possibly eliminate the need for costlier methods such as gravure printing and paves the way to industrial manufacturing of prudent electronic devices.

Research paper thumbnail of Fully-ambient-processed mesoscopic semitransparent perovskite solar cells by islands-structure-MAPbI3-xClx-NiO composite and Al2O3/NiO interface engineering

Nano Energy, 2018

Perovskite solar cells (PSCs) because of low-cost fabrication and high performance have shown sup... more Perovskite solar cells (PSCs) because of low-cost fabrication and high performance have shown superb potential for the next-generation photovoltaic application. For the potential applications of photovoltaic technologies, semitransparent PSCs are also highly attractive and of commercial interest to develop building-and tandem-integrated solar cells. Here, we present fully-ambientprocessed stable and mesoscopic semitransparent PSCs by non-continuous islands-structure-CH 3 NH 3 PbI 3-x Cl x-NiO nanoparticles (MAPbI 3-x Cl x-NiO NPs) composite and interface engineering by inserting Al 2 O 3 /NiO between TiO 2 and MAPbI 3-x Cl x-NiO composite layers in a device configuration of FTO/c-TiO 2 /mp-TiO 2 /Al 2 O 3 /NiO/islands-structure-MAPbI 3-x Cl x-NiO /spiro-OMeTAD/Au. Except for the islands-structure-MAPbI 3-x Cl x-NiO capping layer, a uniform and thicker and transparent TiO 2 /Al 2 O 3 /NiO/MAPbI 3-x Cl x composite layer is formed, which can effectively reduce photocurrent density loss and interface recombination. Interestingly, the optimized semitransparent PSCs showed hysteresis-free performance. The average visible transmittance (AVT) of MAPbI 3-x Cl x-NiO NPs composite film was ranged from 18% to 56% and the corresponding device PCE changed from 17.51% to 12.47%. The PSCs without encapsulation showed an excellent air stability over 270 days with retaining ~98% of its original V oc , ~96% of J sc , ~97% of FF and ~93% of PCE under ambient condition (25-30℃ and 45-50 % humidity). Finally, we achieved semitransparent device of PCE = 10.

Research paper thumbnail of Graphene and its derivatives for solar cells application

Nano Energy, 2018

Graphene has played the role of game-changer for conductive transparent devices indebted to its u... more Graphene has played the role of game-changer for conductive transparent devices indebted to its unique two dimensional (2D) structures and gained an exceptional opportunity to be employed in energy industry. In the past two decades graphene has been merged with the concept of photovoltaic (PV) material and exhibited a significant role as a transparent electrode, hole/electron transport material and interfacial buffer layer in solar cell devices. This review covers the different methods of graphene fabrication and broadly discusses the recent advances in graphene-based solar cells, including bulk heterojunction (BHJ) organic, dye-sensitized and perovskite solar cell deices. The power conversion efficiency surpassed 20.3 % for graphene-based perovskite solar cells and hit the efficiency of 10 % for BHJ organic solar cells. Except the part of charge extracting and transport to the electrodes, graphene has another unique role of device protection against environmental degradation via its packed 2D network structure and provides long-term environmental stability for PV devices. We highlighted a comparative study on the role of graphene and its derivatives in photovoltaic devices. After all, the potential issues and the perspective for future research in graphene-based materials for PV applications are presented.

Research paper thumbnail of Efficient bulk heterojunction hybrid solar cells with graphene-silver nanoparticles composite synthesized by microwave-assisted reduction

Nano Energy, 2016

Herein, we present a simple, eco-friendly one-step microwave-assisted reduction (MWAR) that can p... more Herein, we present a simple, eco-friendly one-step microwave-assisted reduction (MWAR) that can produce silver nanoparticles (Ag NPs) and reduced graphene oxide (rGO) in the form of Ag-rGO composites for application in heterojunction hybrid solar cells. The field-effect transistor fabricated with the MWAR Ag-rGO composite showed p-type behavior with a high mobility of 3.3x10 5 cm 2 V-1 s-1 and conductivity of 9x10 6 S/m which is one-order of magnitude greater than pristine graphene (i.e., 1.59x10 5 S/m). As-synthesized Ag-rGO composite was introduced into the active layer of bulk heterojunction solar cell based on P3HT:PCBM. Compared to the P3HT:PCBM only device (i.e., control device), the Ag-rGO implemented device showed a power conversion efficiency (PCE) of 4.23 %, which is about 42 % increase over the control device (i.e. PCE=2.98 %). This dramatic increase in PCE was found to be mainly due to an increase in short-circuit current (J sc) from 9.55 to 12.76 mA/cm 2 (about 33 % increase), suggesting that the incorporation of p-type Ag-rGO into the active layer enhances the charge carrier generation and fast extraction of holes to the electrode. Furthermore, the Ag-rGO composite based solar cells without encapsulation showed remarkable air stability with retaining ~90 % of its original PCE and ~93% of J sc for 30 days under ambient environment, attributed to gas barrier feature of the randomly distributed graphene sheets.

Research paper thumbnail of Ambient-air-solution-processed efficient and highly stable perovskite solar cells based on CH3NH3PbI3−xClx-NiO composite with Al2O3/NiO interfacial engineering

Nano Energy, 2017

The poor air-stability and reproducibility of perovskite solar cells (PSCs) have prevented the pr... more The poor air-stability and reproducibility of perovskite solar cells (PSCs) have prevented the practical applications of the devices that can withstand sustained operation under ambient air conditions. Here, we report all-ambient-air-solution-processed PSCs based on CH 3 NH 3 PbI 3-x Cl x-NiO composite film with inserting Al 2 O 3 /NiO at the TiO 2 /perovskite interface in a cell configuration of FTO/c-TiO 2 /mp-TiO 2 /Al 2 O 3 /NiO/MAPbI 3-x Cl x-NiO/spiro-OMeTAD/Au. The interface engineering with Al 2 O 3 /NiO not only improves crystalline quality of perovskite films and enhances charge transport, but also effectively suppresses carrier recombination. This composite-based interface engineering PSCs showed a high power conversion efficiency (PCE) of 18.14 % and excellent reproducibility with average 16-18 % PCE for 35 devices. More importantly, the devices without encapsulation showed a significant enhancement in long-term air-stability; the device photovoltaic parameters stabilized after 20 days and sustained its stability over 210 days with retaining ~100% of its original V oc , ~94% of J sc , ~91% of FF and ~86% of PCE in an ambient environment.