Giacomo Piana - Academia.edu (original) (raw)

Papers by Giacomo Piana

Research paper thumbnail of CCDC 1995103: Experimental Crystal Structure Determination

Research paper thumbnail of Sol-gel silica films embedding NIR- emitting Yb-quinolinolate complexes

Nucleation and Atmospheric Aerosols, 2014

Thickness controlled sol-gel silica films for plasmonic bio-sensing devices

Research paper thumbnail of Phonon-Assisted Trapping and Re-excitation of Free Carriers and Excitons in Lead Halide Perovskites

Journal of Physical Chemistry C, Jul 21, 2019

Despite the advances in solar cells based on lead halide perovskites, the nature of photogenerate... more Despite the advances in solar cells based on lead halide perovskites, the nature of photogenerated charges and trap states within these materials remains unclear. A model describing recombination in CH 3 NH 3 PbI 3-x Cl x has been developed that accounts for phonon-assisted free-exciton and freecarrier trapping. We utilize optical spectroscopies and observe significant coexistence of the tetragonal and orthorhombic structural phases at low temperatures. From these measurements, we evaluate the longitudinal-optical phonon energy, exciton binding energy and temperaturedependent electronic bandgap. We use these parameters to model the temperature-and fluencedependent time-resolved photoluminescence decays, enabling us to demonstrate how shallow traps from which carriers can be re-excited can account for the delayed recombination in lead halide perovskites. The trap-state density reaches a maximum at the tetragonal to orthorhombic phase transition at ~140 K, suggesting the formation of disorder-induced trap states, which are shown to dominate the recombination dynamics in CH 3 NH 3 PbI 3-x Cl x .

Research paper thumbnail of Lateral Growth of MoS <sub>2</sub> 2D Material Semiconductors Over an Insulator Via Electrodeposition

Advanced electronic materials, Jun 30, 2021

Some of these demonstrations were implemented for wearable applications by exploiting the materia... more Some of these demonstrations were implemented for wearable applications by exploiting the material's exceptional robustness and flexibility. [5,6] However, there remain major obstacles that hinder the industrial adoption of MoS 2 and other 2D TMDC materials. The most challenging obstacle has been finding an industrially compatible method that enables the production of these materials on a mass scale. We have recently demonstrated that electrodeposition is a potentially viable method for solving this challenge. [7,8] Electrodeposition offers important advantages in 2D material production over other methods such as chemical vapor deposition (CVD), [9,10] sputtering, [11] or atomic layer deposition (ALD). [12] Electrodeposition is not a lineof-sight deposition method as material growth occurs at electrical contacts and is controlled by electrical potential or current. [13] It can hence be utilized to deposit materials over 3D surfaces including patterned nanostructures of high aspect ratios. [14-17] In addition, electrodeposition is usually performed at room temperature, avoiding harsh environments such as plasma or extremely high temperatures, which can damage pre-existing materials on the substrate, such as graphene electrodes. [7] However, there is an important limitation with electrodeposition that needs to be overcome. This method requires an electrically conductive surface from which materials are traditionally grown vertically. [18] Depositing a semiconductor material on a conductor provides a low resistance current path in planar (opto-) electronic devices such as transistors and photodetectors, thus limiting the use of electrodeposition traditionally to certain vertical device structures or metal interconnects (through the dual damascene process). [19] Prior to the work described herein, this limitation has been a drawback, specifically for developing 2D material based devices where planar structures that exploit the unique 2D properties of the material are the "natural" route forward. [20-23] Creating innovative techniques to electrodeposit planar 2D materials over non-conducting surfaces would solve this limitation and open new routes where the insulator base can be utilized, such as in transistor gating. In the early 1990s, Nishizawa et al. described the electrochemical growth of poly(pyrrole) Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum disulfide (MoS 2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS 2 2D films grown from TiN electrodes across opposite sides are connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS 2 is shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photo-response measurements on the device structures demonstrate that the electrodeposited MoS 2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way toward room temperature, scalable, and site-selective production of various transition metal dichalcogenides and their lateral heterostructures for 2D materials-based fabricated devices.

Research paper thumbnail of Solution processed blue light emitting electrochemical cells fabricated and encapsulated fully in ambient environment

2021 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), Jun 20, 2021

Light emitting devices such as OLECs are one form of electronic device that can be integrated int... more Light emitting devices such as OLECs are one form of electronic device that can be integrated into garments to realise light emitting textiles. In the development of wearable electrical devices, conductive organic materials such as conducting polymers, with the ability to emit light in almost all colours of the spectrum, could substitute expensive and complex in synthesis inorganic materials or metals. In this paper, we report the solution processed fabrication method of OLECs on ITO coated glass substrates using commercially available blue emitter (Merck NCMP) as the active layer. The fabrication and encapsulation process were done fully in the ambient environment for the first time. The optical and electrical performance of the blue emitting LECs have been demonstrated in operation in ambient environment. An encapsulation process was used to protect the glass based OLECs from oxygen and moisture, and to increase the stability and lifetime of the device performance as well as protecting against external physical damage. The devices show the brightness level of 472 cd/m 2 and the driven voltage of 6 V with bright light emission. Keywords-e-textiles, light emission, light emitting textiles, light emitting electrochemical cells, printing electronics. I.

Research paper thumbnail of High-energy optical transitions and optical constants of CH$_3$NH$_3$PbI$_3$ measured by spectroscopic ellipsometry and spectrophotometry

ePrints Soton (University of Southampton), Sep 9, 2019

Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, followin... more Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, following more than a decade of research. For prime routes of commercialization such as tandem solar cells, optical modeling is essential for engineering device architectures, which requires accurate optical data for the materials utilized. Additionally, a comprehensive understanding of the fundamental material properties is vital for simulating the operation of devices for design purposes. In this article, we use variable angle spectroscopic ellipsometry (SE) to determine the optical constants of CH 3 NH 3 PbI 3 (MAPbI 3) thin films over a photon energy range of 0.73 to 6.45 eV. We successfully model the ellipsometric data using six Tauc-Lorentz oscillators for three different incident angles. Following this, we use critical-point analysis of the complex 1

Research paper thumbnail of Low-dimensional emissive states in non-stoichiometric methylammonium lead halide perovskites

Journal of materials chemistry. A, Materials for energy and sustainability, 2019

This is a repository copy of Low-dimensional emissive states in non-stoichiometric methylammonium... more This is a repository copy of Low-dimensional emissive states in non-stoichiometric methylammonium lead halide perovskites.

Research paper thumbnail of High-Energy Optical Transitions and Optical Constants of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Measured by Spectroscopic Ellipsometry and Spectrophotometry

Journal of Physical Chemistry C, Nov 6, 2019

Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, followin... more Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, following more than a decade of research. For prime routes of commercialization such as tandem solar cells, optical modeling is essential for engineering device architectures, which requires accurate optical data for the materials utilized. Additionally, a comprehensive understanding of the fundamental material properties is vital for simulating the operation of devices for design purposes. In this article, we use variable angle spectroscopic ellipsometry (SE) to determine the optical constants of CH 3 NH 3 PbI 3 (MAPbI 3) thin films over a photon energy range of 0.73 to 6.45 eV. We successfully model the ellipsometric data using six Tauc-Lorentz oscillators for three different incident angles. Following this, we use critical-point analysis of the complex 1

Research paper thumbnail of Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

Materials horizons, 2020

Large amplitude motions in molecular solids are responsible for anomalous electrical characterist... more Large amplitude motions in molecular solids are responsible for anomalous electrical characteristics in amphidynamic crystals. We study the effect of orientational dipolar disorder on charge transfer excitons (CTEs) in a donor-acceptor amphidynamic co-crystal of perylene-tetrabromophthalic anhydride (-TBPA). This co-crystal offers long range positional order of alternating donor and acceptor molecular entities arranged in stacks. Further it has a phase transition at 250 K due to progressive freezing of the dipolar orientational motion in the TBPA permanent dipole. The optical absorption band and photoluminescence at the semiconductor gap consists of at least three energetically separated CTE resonances that cover a spectral range of more than 400 meV. As the temperature is lowered below the phase transition the CTE band remains broad, but shows a shift of B150 meV to higher energy. On the basis of optical reflectivity, photoluminescence, and model calculations we interpret the room temperature CTE band as a collection of resonances in which at least one the nearest neighbour dipoles to the CTE is flipped from their lowest energy configuration. This first comprehensive optical investigation on an amphidynamic co-crystal demonstrates the importance of understanding the role of permanent dipoles in the CTE photophysics of organic semiconductors.

Research paper thumbnail of Lateral electrodeposition of MoS2 semiconductor over an insulator

arXiv (Cornell University), Apr 1, 2021

Developing novel techniques for depositing transition metal dichalcogenides is crucial for the in... more Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum disulfide (MoS2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS2 2D films grown from TiN electrodes across opposite sides have been connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS2 has been shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photoresponse measurements on the device structures demonstrate that the electrodeposited MoS2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way towards room temperature, scalable and siteselective production of various transition metal dichalcogenides and their lateral heterostructures for 2D materials-based fabricated devices.

Research paper thumbnail of Effect of dipole orientational order on charge transfer exciton states in a donor-acceptor single crystal

Bulletin of the American Physical Society, Mar 17, 2021

Research paper thumbnail of Carrier recombination kinetics in organometal trihalide perovskites thin films

Research paper thumbnail of Resonant energy transfer properties of perovskite nanocrystals

Perovskite nanocrystals of the form FAPbBr3 display significant promise in the field of optoelect... more Perovskite nanocrystals of the form FAPbBr3 display significant promise in the field of optoelectronics. In particular, these nanocrystals could bridge the `green gap' of LED technology, and also serve to down-convert ultraviolet light for harvesting using silicon-based photovoltaic cells. To remain competitive with traditional devices, optimising the energy transfer between the nanocrystal and the device is crucial, however very little investigation has been performed into this subject. Here, we characterise the energy transfer dynamics of FAPbBr3 nanocrystals on a silicon substrate using time resolved photoluminescence. We also use deposited `spacer layers' to vary the displacement of the nanocrystals from the silicon in order to observe the effect on the energy-transfer dynamics. We find that the overall photo luminescent lifetime increases when reducing the distance between between the nanocrystals and the silicon layer, which runs counter to the expected behaviour. This suggests that the presence of an optically-active substrate suppresses photo luminescent lifetime and, further, suggests that nanocrystal-to-nanocrystal transfer is highly efficient.

Research paper thumbnail of Effect of dipole orientational order on charge transfer exciton states in a donor-acceptor single crystal

Bulletin of the American Physical Society, Mar 17, 2021

Research paper thumbnail of Carrier recombination kinetics in organometal trihalide perovskites thin films

University of Southampton, Mar 1, 2019

Research paper thumbnail of Printable biflourene based ultra-violet (UV) organic light-emitting electrochemical cells (OLECs) with improved device performance

Organic Electronics, 2022

Research paper thumbnail of CCDC 1995104: Experimental Crystal Structure Determination

Research paper thumbnail of Low-temperature LPE growth and characterization of InGaAsN thick layers

Energy Procedia, 2011

This work demonstrates the possibility for low-temperature Liquid-Phase Epitaxy (LPE) growth of l... more This work demonstrates the possibility for low-temperature Liquid-Phase Epitaxy (LPE) growth of lattice matched to GaAs substrate dilute nitride InGaAsN layers with good crystalline quality and high Hall electron mobility. X-ray microanalysis and X-ray diffraction methods have been used to determine the composition and crystalline quality of the grown InGaAsN layers. Surface roughness is examined by atomic force microscopy. N-related local vibration modes are observed by Raman scattering. The Hall electron mobility and free carrier concentration have been measured in the temperature range 80-300K by conventional Van der Pauw method.

Research paper thumbnail of Lateral electrodeposition of MoS2 semiconductor over an insulator

Developing novel techniques for depositing transition metal dichalcogenides is crucial for the in... more Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum disulfide (MoS2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS2 2D films grown from TiN electrodes across opposite sides have been connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS2 has been shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photoresponse measurements on the device structures demonstrate that the electrodeposited MoS2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way towards room temperature, scalable a...

Research paper thumbnail of Lateral growth of MoS2 2D material semiconductors over an insulator via electrodeposition

Developing novel techniques for depositing transition metal dichalcogenides is crucial for the in... more Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, we have demonstrated lateral growth of molybdenum disulfide (MoS2) over an insulating surface using electrochemical deposition. By fabricating a novel electrode structure, we can connect electrodeposited MoS2 grown from TiN electrodes on opposite sides across an insulating substrate, thus forming a lateral device structure using just one lithography and deposition step. Using a variety of characterisation techniques, we have shown that the lateral growth rate of MoS2 is over 20 times higher than its vertical growth rate. We performed electronic and photo-response measurements on the device structures and confirmed that our material behaves like semiconducting MoS2, confirming its potential for photodetection applications. This result paves the way towards developing the lateral growth electrodeposition technique for othe...

Research paper thumbnail of CCDC 1995103: Experimental Crystal Structure Determination

Research paper thumbnail of Sol-gel silica films embedding NIR- emitting Yb-quinolinolate complexes

Nucleation and Atmospheric Aerosols, 2014

Thickness controlled sol-gel silica films for plasmonic bio-sensing devices

Research paper thumbnail of Phonon-Assisted Trapping and Re-excitation of Free Carriers and Excitons in Lead Halide Perovskites

Journal of Physical Chemistry C, Jul 21, 2019

Despite the advances in solar cells based on lead halide perovskites, the nature of photogenerate... more Despite the advances in solar cells based on lead halide perovskites, the nature of photogenerated charges and trap states within these materials remains unclear. A model describing recombination in CH 3 NH 3 PbI 3-x Cl x has been developed that accounts for phonon-assisted free-exciton and freecarrier trapping. We utilize optical spectroscopies and observe significant coexistence of the tetragonal and orthorhombic structural phases at low temperatures. From these measurements, we evaluate the longitudinal-optical phonon energy, exciton binding energy and temperaturedependent electronic bandgap. We use these parameters to model the temperature-and fluencedependent time-resolved photoluminescence decays, enabling us to demonstrate how shallow traps from which carriers can be re-excited can account for the delayed recombination in lead halide perovskites. The trap-state density reaches a maximum at the tetragonal to orthorhombic phase transition at ~140 K, suggesting the formation of disorder-induced trap states, which are shown to dominate the recombination dynamics in CH 3 NH 3 PbI 3-x Cl x .

Research paper thumbnail of Lateral Growth of MoS <sub>2</sub> 2D Material Semiconductors Over an Insulator Via Electrodeposition

Advanced electronic materials, Jun 30, 2021

Some of these demonstrations were implemented for wearable applications by exploiting the materia... more Some of these demonstrations were implemented for wearable applications by exploiting the material's exceptional robustness and flexibility. [5,6] However, there remain major obstacles that hinder the industrial adoption of MoS 2 and other 2D TMDC materials. The most challenging obstacle has been finding an industrially compatible method that enables the production of these materials on a mass scale. We have recently demonstrated that electrodeposition is a potentially viable method for solving this challenge. [7,8] Electrodeposition offers important advantages in 2D material production over other methods such as chemical vapor deposition (CVD), [9,10] sputtering, [11] or atomic layer deposition (ALD). [12] Electrodeposition is not a lineof-sight deposition method as material growth occurs at electrical contacts and is controlled by electrical potential or current. [13] It can hence be utilized to deposit materials over 3D surfaces including patterned nanostructures of high aspect ratios. [14-17] In addition, electrodeposition is usually performed at room temperature, avoiding harsh environments such as plasma or extremely high temperatures, which can damage pre-existing materials on the substrate, such as graphene electrodes. [7] However, there is an important limitation with electrodeposition that needs to be overcome. This method requires an electrically conductive surface from which materials are traditionally grown vertically. [18] Depositing a semiconductor material on a conductor provides a low resistance current path in planar (opto-) electronic devices such as transistors and photodetectors, thus limiting the use of electrodeposition traditionally to certain vertical device structures or metal interconnects (through the dual damascene process). [19] Prior to the work described herein, this limitation has been a drawback, specifically for developing 2D material based devices where planar structures that exploit the unique 2D properties of the material are the "natural" route forward. [20-23] Creating innovative techniques to electrodeposit planar 2D materials over non-conducting surfaces would solve this limitation and open new routes where the insulator base can be utilized, such as in transistor gating. In the early 1990s, Nishizawa et al. described the electrochemical growth of poly(pyrrole) Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum disulfide (MoS 2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS 2 2D films grown from TiN electrodes across opposite sides are connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS 2 is shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photo-response measurements on the device structures demonstrate that the electrodeposited MoS 2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way toward room temperature, scalable, and site-selective production of various transition metal dichalcogenides and their lateral heterostructures for 2D materials-based fabricated devices.

Research paper thumbnail of Solution processed blue light emitting electrochemical cells fabricated and encapsulated fully in ambient environment

2021 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), Jun 20, 2021

Light emitting devices such as OLECs are one form of electronic device that can be integrated int... more Light emitting devices such as OLECs are one form of electronic device that can be integrated into garments to realise light emitting textiles. In the development of wearable electrical devices, conductive organic materials such as conducting polymers, with the ability to emit light in almost all colours of the spectrum, could substitute expensive and complex in synthesis inorganic materials or metals. In this paper, we report the solution processed fabrication method of OLECs on ITO coated glass substrates using commercially available blue emitter (Merck NCMP) as the active layer. The fabrication and encapsulation process were done fully in the ambient environment for the first time. The optical and electrical performance of the blue emitting LECs have been demonstrated in operation in ambient environment. An encapsulation process was used to protect the glass based OLECs from oxygen and moisture, and to increase the stability and lifetime of the device performance as well as protecting against external physical damage. The devices show the brightness level of 472 cd/m 2 and the driven voltage of 6 V with bright light emission. Keywords-e-textiles, light emission, light emitting textiles, light emitting electrochemical cells, printing electronics. I.

Research paper thumbnail of High-energy optical transitions and optical constants of CH$_3$NH$_3$PbI$_3$ measured by spectroscopic ellipsometry and spectrophotometry

ePrints Soton (University of Southampton), Sep 9, 2019

Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, followin... more Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, following more than a decade of research. For prime routes of commercialization such as tandem solar cells, optical modeling is essential for engineering device architectures, which requires accurate optical data for the materials utilized. Additionally, a comprehensive understanding of the fundamental material properties is vital for simulating the operation of devices for design purposes. In this article, we use variable angle spectroscopic ellipsometry (SE) to determine the optical constants of CH 3 NH 3 PbI 3 (MAPbI 3) thin films over a photon energy range of 0.73 to 6.45 eV. We successfully model the ellipsometric data using six Tauc-Lorentz oscillators for three different incident angles. Following this, we use critical-point analysis of the complex 1

Research paper thumbnail of Low-dimensional emissive states in non-stoichiometric methylammonium lead halide perovskites

Journal of materials chemistry. A, Materials for energy and sustainability, 2019

This is a repository copy of Low-dimensional emissive states in non-stoichiometric methylammonium... more This is a repository copy of Low-dimensional emissive states in non-stoichiometric methylammonium lead halide perovskites.

Research paper thumbnail of High-Energy Optical Transitions and Optical Constants of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Measured by Spectroscopic Ellipsometry and Spectrophotometry

Journal of Physical Chemistry C, Nov 6, 2019

Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, followin... more Optoelectronics based on metal halide perovskites (MHPs) have shown substantial promise, following more than a decade of research. For prime routes of commercialization such as tandem solar cells, optical modeling is essential for engineering device architectures, which requires accurate optical data for the materials utilized. Additionally, a comprehensive understanding of the fundamental material properties is vital for simulating the operation of devices for design purposes. In this article, we use variable angle spectroscopic ellipsometry (SE) to determine the optical constants of CH 3 NH 3 PbI 3 (MAPbI 3) thin films over a photon energy range of 0.73 to 6.45 eV. We successfully model the ellipsometric data using six Tauc-Lorentz oscillators for three different incident angles. Following this, we use critical-point analysis of the complex 1

Research paper thumbnail of Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

Materials horizons, 2020

Large amplitude motions in molecular solids are responsible for anomalous electrical characterist... more Large amplitude motions in molecular solids are responsible for anomalous electrical characteristics in amphidynamic crystals. We study the effect of orientational dipolar disorder on charge transfer excitons (CTEs) in a donor-acceptor amphidynamic co-crystal of perylene-tetrabromophthalic anhydride (-TBPA). This co-crystal offers long range positional order of alternating donor and acceptor molecular entities arranged in stacks. Further it has a phase transition at 250 K due to progressive freezing of the dipolar orientational motion in the TBPA permanent dipole. The optical absorption band and photoluminescence at the semiconductor gap consists of at least three energetically separated CTE resonances that cover a spectral range of more than 400 meV. As the temperature is lowered below the phase transition the CTE band remains broad, but shows a shift of B150 meV to higher energy. On the basis of optical reflectivity, photoluminescence, and model calculations we interpret the room temperature CTE band as a collection of resonances in which at least one the nearest neighbour dipoles to the CTE is flipped from their lowest energy configuration. This first comprehensive optical investigation on an amphidynamic co-crystal demonstrates the importance of understanding the role of permanent dipoles in the CTE photophysics of organic semiconductors.

Research paper thumbnail of Lateral electrodeposition of MoS2 semiconductor over an insulator

arXiv (Cornell University), Apr 1, 2021

Developing novel techniques for depositing transition metal dichalcogenides is crucial for the in... more Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum disulfide (MoS2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS2 2D films grown from TiN electrodes across opposite sides have been connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS2 has been shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photoresponse measurements on the device structures demonstrate that the electrodeposited MoS2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way towards room temperature, scalable and siteselective production of various transition metal dichalcogenides and their lateral heterostructures for 2D materials-based fabricated devices.

Research paper thumbnail of Effect of dipole orientational order on charge transfer exciton states in a donor-acceptor single crystal

Bulletin of the American Physical Society, Mar 17, 2021

Research paper thumbnail of Carrier recombination kinetics in organometal trihalide perovskites thin films

Research paper thumbnail of Resonant energy transfer properties of perovskite nanocrystals

Perovskite nanocrystals of the form FAPbBr3 display significant promise in the field of optoelect... more Perovskite nanocrystals of the form FAPbBr3 display significant promise in the field of optoelectronics. In particular, these nanocrystals could bridge the `green gap' of LED technology, and also serve to down-convert ultraviolet light for harvesting using silicon-based photovoltaic cells. To remain competitive with traditional devices, optimising the energy transfer between the nanocrystal and the device is crucial, however very little investigation has been performed into this subject. Here, we characterise the energy transfer dynamics of FAPbBr3 nanocrystals on a silicon substrate using time resolved photoluminescence. We also use deposited `spacer layers' to vary the displacement of the nanocrystals from the silicon in order to observe the effect on the energy-transfer dynamics. We find that the overall photo luminescent lifetime increases when reducing the distance between between the nanocrystals and the silicon layer, which runs counter to the expected behaviour. This suggests that the presence of an optically-active substrate suppresses photo luminescent lifetime and, further, suggests that nanocrystal-to-nanocrystal transfer is highly efficient.

Research paper thumbnail of Effect of dipole orientational order on charge transfer exciton states in a donor-acceptor single crystal

Bulletin of the American Physical Society, Mar 17, 2021

Research paper thumbnail of Carrier recombination kinetics in organometal trihalide perovskites thin films

University of Southampton, Mar 1, 2019

Research paper thumbnail of Printable biflourene based ultra-violet (UV) organic light-emitting electrochemical cells (OLECs) with improved device performance

Organic Electronics, 2022

Research paper thumbnail of CCDC 1995104: Experimental Crystal Structure Determination

Research paper thumbnail of Low-temperature LPE growth and characterization of InGaAsN thick layers

Energy Procedia, 2011

This work demonstrates the possibility for low-temperature Liquid-Phase Epitaxy (LPE) growth of l... more This work demonstrates the possibility for low-temperature Liquid-Phase Epitaxy (LPE) growth of lattice matched to GaAs substrate dilute nitride InGaAsN layers with good crystalline quality and high Hall electron mobility. X-ray microanalysis and X-ray diffraction methods have been used to determine the composition and crystalline quality of the grown InGaAsN layers. Surface roughness is examined by atomic force microscopy. N-related local vibration modes are observed by Raman scattering. The Hall electron mobility and free carrier concentration have been measured in the temperature range 80-300K by conventional Van der Pauw method.

Research paper thumbnail of Lateral electrodeposition of MoS2 semiconductor over an insulator

Developing novel techniques for depositing transition metal dichalcogenides is crucial for the in... more Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, the lateral growth of molybdenum disulfide (MoS2) over an insulating surface is demonstrated using electrochemical deposition. By fabricating a new type of microelectrodes, MoS2 2D films grown from TiN electrodes across opposite sides have been connected over an insulating substrate, hence, forming a lateral device structure through only one lithography and deposition step. Using a variety of characterization techniques, the growth rate of MoS2 has been shown to be highly anisotropic with lateral to vertical growth ratios exceeding 20-fold. Electronic and photoresponse measurements on the device structures demonstrate that the electrodeposited MoS2 layers behave like semiconductors, confirming their potential for photodetection applications. This lateral growth technique paves the way towards room temperature, scalable a...

Research paper thumbnail of Lateral growth of MoS2 2D material semiconductors over an insulator via electrodeposition

Developing novel techniques for depositing transition metal dichalcogenides is crucial for the in... more Developing novel techniques for depositing transition metal dichalcogenides is crucial for the industrial adoption of 2D materials in optoelectronics. In this work, we have demonstrated lateral growth of molybdenum disulfide (MoS2) over an insulating surface using electrochemical deposition. By fabricating a novel electrode structure, we can connect electrodeposited MoS2 grown from TiN electrodes on opposite sides across an insulating substrate, thus forming a lateral device structure using just one lithography and deposition step. Using a variety of characterisation techniques, we have shown that the lateral growth rate of MoS2 is over 20 times higher than its vertical growth rate. We performed electronic and photo-response measurements on the device structures and confirmed that our material behaves like semiconducting MoS2, confirming its potential for photodetection applications. This result paves the way towards developing the lateral growth electrodeposition technique for othe...