Semiconductor and Optical Materials Commons^™

Preparations And Photoelectrochemical Properties Of Phosphate Modified Rgo-Biobr Nanocomposites, Shuang-Ying Chen, Zhi-Jun Li, Xu-Liang Zhang, Kang Hu, Rui Yan, Li-Qiang Jing

Journal of Electrochemistry

The RGO-BiOBr nanocomposites have been successfully synthesized by a hydrothermal process, and then modified with phosphorous acids. The photoelectrochemical properties of the fabricated RGO-BiOBr nanocomposite films were studied. The results indicate that the photocurrent densities of RGO-BiOBr were much larger compared with those of the bare BiOBr, and interestingly, the photocurrent densities were further improved after phosphate modification. Based on the analyses of the produced hydroxyl radical amounts, the enhanced photocurrent densities could be attributed to the introduction of RGO and to the formed negative fields of modified phosphate groups, which are favorable for electrons to be transferred and for …

Cathode Buffer Layer For Improving Photovoltaic Performance Of Planar P-I-N Perovskite Solar Cells, Xiao-Dong Liu, Yong-Fang Li

Journal of Electrochemistry

Organic/inorganic hybrid metal halide perovskite semiconductor materials have drawn great attention for the application in solar cells in recent years because of their combined superior photoelectrical properties of inorganic semiconductors (with high dielectric constant and high charge carriers mobility) and organic semiconductors (with good solution processability and high absorbance). The power conversion efficiency (PCE) of the organometal halide perovskite solar cells (pero-SCs) based on CH₃NH₃PbI₃ has been increased dramatically in a few years from 3.8% to a certified 22.1%, primarily owing to the development of new interfacial materials, careful optimization of morphology, and perovskite crystallization …

Special Issue: Photoelectrochemistry And New Types Of Solar Cells, Chang-Jian Lin, Yong-Fang Li

Journal of Electrochemistry

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Prospects Of D-Π-A Structured Porphyrins And Their Photoelectrochemical Application, Shuang-Shuang Liu, Jian-Feng Lu, Ming-Kui Wang

Journal of Electrochemistry

Porphyrins and their metalloderivatives are a class of compounds exhibiting a wide variety of interesting and highly useful properties, such as chlorophyll. Porphyrins are particularly interesting in photoelectrochemical applications due to their structural similarity to chlorophylls in natural photosynthetic systems, as well as their strong and tunable absorption properties. Recently, various porphyrins have been extensively studied for their applications in solar cells, photocatalytic hydrogen production, optical information storage and others. This review will focus on the unique physical and chemical properties of D-π-A structured porphyrins, and their photovoltaic performances in dye-sensitized solar cells. A brief discussion in the future development …

Photonicstd-2d: Modeling Light Scattering In Periodic Multilayer Photonic Structures, Alexey Bondarev, Shaimaa Azzam, Zhaxylyk Kudyshev, Alexander V. Kildishev

The Summer Undergraduate Research Fellowship (SURF) Symposium

Efficient modeling of electromagnetic processes in optical and plasmonic metamaterials is important for enabling new and exciting ways to manipulate light for advanced applications. In this work, we put together a tool for numerical simulation of propagation of normally incident light through a nanostructured multilayer composite material. The user builds a unit cell of a given material layer-by-layer starting from a substrate up to a superstrate, splitting each layer further into segments. The segments are defined by width and material -- dielectric, metal or active medium. Simulations are performed with the finite difference time domain (FDTD) method. A database of …

Thermoelectric Half-Heuslers: Synthesis, Processing, And Performance, Joseph Robert Croteau

Boise State University Theses and Dissertations

Thermoelectric half-Heusler compounds have potential to convert the heat wasted from industrial and transportation processes to useful electricity. Among the highest performing half-Heusler compounds are nano-structured bulk materials which have been arc-melted, pulverized into a nano-powder, and sintered by DC-hot press. High performing n- and p-type half-Heusler compounds with nominal composition of Hf_0.25Zr_0.75NiSn_0.99Sb_0.01 and Nb_0.75Ti_0.25FeSb, respectively, have been provided to us in both dense and powder form by our collaborators at the University of Houston. We consolidate these powders by SPS, refine these powders to improve both particle size …

Zno Thin Films Generated By Ex-Situ Thermal Oxidation Of Metallic Zn For Photovoltaic Applications, Kovas Zygas

Macalester Journal of Physics and Astronomy

ZnO thin films that function as either transparent conducting oxides in solid-state photovoltaic cells or as nanocrystalline dye-absorbers in dye-sensitized solar cells have the potential to reduce the cost of producing electricity from solar energy. Although there exist many methods to produce ZnO thin films, the most economical and practical method may be oxidation of metallic Zn thin films. This research examined the utility of ex-situ thermal oxidation of DC magnetron sputtered Zn thin films in generating useful ZnO thin films for these photovoltaic applications. We annealed Zn thin films in air at 570° C in order to produce ZnO …

Synthesis Of Acceptors For Use In Donor-Acceptor Copolymers And Characterization Of These Polymers, William D. Walker

Honors Theses

In this thesis, a selenium-derivatized acceptor was synthesized to examine the heavy atom effects of selenium on the position of the frontier molecular orbitals (HOMO/LUMO band gap) as opposed to sulfur in a donor-acceptor copolymer for use in light harvesting and detection applications. Over the course of this research, standard operating protocols for ultraviolet-visible (UV-Vis-NIR) and Fourier transform infrared (FT-IR) spectroscopies, as well as cyclic voltammetry (CV) characterization techniques were established. Once synthesized, the polymers were characterized through use of the established characterization protocols. The selenium-derivatized polymer exhibited a bathochromic shift compared to the sulfur analogue, with a solid-state absorption …

Direct Band Gap Gallium Antimonide Phosphide (Gasbxp1-X) For Solar Fuels., Harry Benjamin Russell

Electronic Theses and Dissertations

Photoelectrochemical water splitting has been identified as a promising route for achieving sustainable energy future. However, semiconductor materials with the appropriate optical, electrical and electrochemical properties have yet to be discovered. In search of an appropriate semiconductor to fill this gap, GaSbP, a semiconductor never tested for PEC performance is proposed here and investigated. Density functional theory (DFT+U) techniques were utilized to predict band gap and band edge energetics for GaSbP alloys with low amount of antimony. The overall objective of this dissertation is to understand the suitability of GaSb_xP_1-x alloys for photoelectrochemical water splitting application. Specifically, …

Synthesis, Characterization, And Electronic Properties Of Novel 2d Materials : Transition Metal Dichalcogenides And Phosphorene., George Anderson

Electronic Theses and Dissertations

Scaling electronic devices has become paramount. The current work builds upon scaling efforts by developing novel synthesis methods and next generation sensing devices based on 2D materials. A new combination method utilizing thermal evaporation and chemical vapor deposition was developed and analyzed to show the possibilities of Transition Metal Dichalcogenide monolayers and heterostructures. The materials produced from the above process showed high degrees of compositional control in both spatial dimensions and chemical structure. Characterization shows controlled fabrication of heterostructures, which may pave the way for future band gap engineering possibilities. In addition, Phosphorene based field effect transistors, photodetectors, and gas …

Identification Of The Zinc-Oxygen Divacancy In Zno Crystals, Maurio S. Holston, Eric M. Golden, Brant E. Kananen, John W. Mcclory, Nancy C. Giles, Larry E. Halliburton

Faculty Publications

An electron paramagnetic resonance (EPR) spectrum in neutron-irradiated ZnO crystals is assigned to the zinc-oxygen divacancy. These divacancies are observed in the bulk of both hydrothermally grown and seeded-chemical-vapor-transport-grown crystals after irradiations with fast neutrons. Neutral nonparamagnetic complexes consisting of adjacent zinc and oxygen vacancies are formed during the irradiation. Subsequent illumination below ∼150 K with 442 nm laser light converts these (V²⁻_Zn − V²⁺_O)⁰ defects to their EPR-active state (V⁻_Zn − V²⁺_O)⁺ as electrons are transferred to donors. The resulting photoinduced S = 1/2 spectrum of the …

Plasma Processing Of Superconducting Radio Frequency Cavities, Janardan Upadhyay

Physics Theses & Dissertations

The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl₂ plasma etching mechanism is crucial for achieving the desired modification of Nb …

Strain Effects On The Work Function Of An Organic Semiconductor, Yanfei Wu, Annabel R. Chew, Geoffrey A. Rojas, Gjergji Sini, Greg Haugstad, Alex Belianinov, Sergei V. Kalinin, Hong Li, Chad Risko, Jean-Luc Brédas, Alberto Salleo, C. Daniel Frisbie

Chemistry Faculty Publications

Establishing fundamental relationships between strain and work function (WF) in organic semiconductors is important not only for understanding electrical properties of organic thin films, which are subject to both intrinsic and extrinsic strains, but also for developing flexible electronic devices. Here we investigate tensile and compressive strain effects on the WF of rubrene single crystals. Mechanical strain induced by thermal expansion mismatch between the substrate and rubrene is quantified by X-ray diffraction. The corresponding WF change is measured by scanning Kelvin probe microscopy. The WF of rubrene increases (decreases) significantly with in-plane tensile (compressive) strain, which agrees qualitatively with density …

Zncdmgse As A Materials Platform For Advanced Photonic Devices: Broadband Quantum Cascade Detectors And Green Semiconductor Disk Lasers, Joel De Jesus

Dissertations, Theses, and Capstone Projects

The ZnCdMgSe family of II-VI materials has unique and promising characteristics that may be useful in practical applications. For example they can be grown lattice matched to InP substrates with lattice matched bandgaps that span from 2.1 to 3.5 eV, they can be successfully doped n-type, have a large conduction band offset (CBO) with no intervalley scattering present when strained, they have lower average phonon energies, and the InP lattice constant lies in the middle of the ZnSe and CdSe binaries compounds giving room to experiment with tensile and compressive stress. However they have not been studied in detail for …

System And Method For Identifying Electrical Properties Of Integrate Circuits, Mary Y. Lanzerotti

AFIT Patents

A new method for displaying electrical properties for integrated circuit (IC) layout designs provides for improved human visualization of those properties and comparison of as designed layout design parameters to as specified layout design parameters and to as manufactured layout parameters. The method starts with a circuitry as designed layout in a first digital format, extracts values for electrical properties from that circuitry as designed layout then annotates those values back into the first digital format. The annotated circuitry as designed layout is then converted from the first digital format to a second digital format that can be converted to …

The Dawn Of New Quantum Dots: Synthesis And Characterization Of Ge1-Xsnx Nanocrystals For Tunable Bandgaps., Richard J. Esteves

Theses and Dissertations

Ge_1-xSn_x alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge_1-xSn_x thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in …

Uv Light-Induced Aggregation Of Titania Submicron Particles, Can Zhou, Yashar Bashirzadeh, Timothy A. Bernadowsky Jr., Xiaoyu Zhang

Mechanical & Aerospace Engineering Faculty Publications

In this study, aggregation of TiO₂ (rutile and anatase) submicron particles in deionized (DI) water under ultra-violet (UV) light irradiation was investigated. While no aggregation was observed in the dark, rutile and anatase submicron particles started aggregating upon application of UV light and ceased aggregation in about 2 and 8.4 h, respectively. It has been demonstrated that UV light directly mitigated the particle mobility of TiO₂, resulting in a neutralization effect of the Zeta potential. It was also observed that rutile particles aggregated much faster than anatase particles under UV radiation, indicating that the Zeta potential of …

Biolabeling Through The Use Of Water-Soluble Colloidal Quantum Dots, Cody Stombaugh

Honors Projects

Nanomaterials continues to be a growing field of study due to their wide range of potential applications. Quantum dots are artificially synthesized crystalline clusters of atoms able to confine electron motion as a result of their incredibly small size. Recently, medical applications of nanomaterials have expanded greatly. Quantum dots are ideal for biolabeling due to their rather narrow photoluminescence emission peaks. By synthesizing quantum dots of a specific diameter, it is possible to predetermine the peak photoluminescence wavelength of a sample. Through ligand exchange and immunoconjugation of the quantum dots with proteins, it is possible to use the quantum dots …

Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian

Theses and Dissertations

Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the “Green Gap”, is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the “quantum confined Stark effect”) and low indium incorporation efficiency that …

Molecular Helices As Electron Acceptors In High-Performance Bulk Heterojunction Solar Cells, Yu Zhong, M. Tuan Trinh, Rongsheng Chen, Geoffrey E. Purdum, Petr P. Khlyabich, Melda Sezen, Seokjoon Oh, Haiming Zhu, Brandon Fowler, Boyuan Zhang, Wei Wang, Chang-Yong Nam, Matthew Y. Sfeir, Charles T. Black, Michael L. Steigerwald, Yueh-Lin Loo, Fay Ng, X.-Y. Zhu, Colin Nuckolls

Publications and Research

Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed …

Morphology-Property Relationship For Binary Organic Thin Films, Alyssa Lynn Griffin

Master's Theses

Organic thin films can be readily mass-produced through solution-based fabrication methods including ink-printing and solution-casting because their light weight, flexibility, and inexpensive sources. Their applications range from organic field-effect transistors (OFET), organic solar cells (OSC), to organic light emitting diodes (OLEDs). Compared with pure component films, binary organic thin films (BOTF) allows for novel characteristics and specialized features to handle more demanding tasks. Due to the complex intermolecular interactions in BOTF, various microscopic phases with different morphological and electronic properties may be formed and this information is difficult to extract through conventional bulk measurements.

Organic thin films can be readily …

Spectrally-Resolved Imaging Of The Transverse Modes In Multimode Vcsels, Stephan A. Misak, Dan G. Dugmore, Kirsten A. Middleton, Evan R. Hale, Kelly R. Farner, Kent D. Choquette, Paul O. Leisher

Rose-Hulman Undergraduate Research Publications

Vertical-cavity surface-emitting lasers (VCSELs) enable a range of applications such as data transmission, trace sensing, atomic clocks, and optical mice. For many of these applications, the output power and beam quality are both critical (i.e. high output power with good beam quality is desired). Multi-mode VCSELs offer much higher power than single-mode devices, but this comes at the expense of lower beam quality. Directly observing the resolved mode structure of multi-mode VCSELs would enable engineers to better understand the underlying physics and help them to develop multi-mode devices with improved beam quality. In this work, a low-cost, high-resolution (<3 >pm) …

Effect Of Surfactant Architecture On Conformational Transitions Of Conjugated Polyelectrolytes, Greg A. Braggin

Master's Theses

Water soluble conjugated polyelectrolytes (CPEs), which fall under the category of conductive polymers, possess numerous advantages over other conductive materials for the fabrication of electronic devices. Namely, the processing of water soluble conjugated polyelectrolytes into thin film electronic devices is much less costly as compared to the processing of inorganic materials. Moreover, the handling of conjugated polyelectrolytes can be performed in a much more environmentally friendly manner than in the processing of other conjugated polymers because conjugated polyelectrolytes are water soluble, whereas other polymers will only dissolve in toxic organic solvents. The processing of electronic devices containing inorganic constituents such …

Interstitial Silicon Ions In Rutile Tio2 Crystals, Eric M. Golden, Nancy C. Giles, Shan Yang, Larry E. Halliburton

Faculty Publications

Electron paramagnetic resonance (EPR) is used to identify a new and unique photoactive silicon-related point defect in single crystals of rutile TiO₂. The importance of this defect lies in its assignment to interstitial silicon ions and the unexpected establishment of silicon impurities as a major hole trap in TiO₂. Principal g values of this new S=1/2 center are 1.9159, 1.9377, and 1.9668 with principal axes along the [¯110],[001], and [110] directions, respectively. Hyperfine structure in the EPR spectrum shows the unpaired spin interacting equally with two Ti nuclei and unequally with two Si nuclei. These silicon …

Towards The Perfect Optical Fiber, John Ballato

Journal of the South Carolina Academy of Science

Optical fibers are being used in an ever more diverse array of applications today. Many of these modern applications are in high-power and, particularly, high power-per-unit-bandwidth systems where optical nonlinearities historically have not limited overall performance. Today, however, nominally weak effects, such as stimulated Brillouin scattering (SBS), are restricting continued scaling to higher optical powers. To address these limitations, the optical fiber industry has focused on fiber geometry-related solutions such as large mode area (LMA) designs. However, since all linear and nonlinear optical phenomena are fundamentally materials-based in origin, this paper identifies material solutions to present and future performance limitations …

Theoretical Investigation Of Stabilities And Optical Properties Of Si12C12 Clusters, Xiaofeng F. Duan, Larry W. Burggraf

Faculty Publications

By sorting through hundreds of globally stable Si₁₂C₁₂ isomers using a potential surface search and using simulated annealing, we have identified low-energy structures. Unlike isomers knit together by Si–C bonds, the lowest energy isomers have segregated carbon and silicon regions that maximize stronger C–C bonding. Positing that charge separation between the carbon and silicon regions would produce interesting optical absorption in these cluster molecules, we used time-dependent density functional theory to compare the calculated optical properties of four isomers representing structural classes having different types of silicon and carbon segregation regions. Absorptions involving charge transfer between segregated …

Monolithic Optofluidic Ring Resonator Lasers Created By Femtosecond Laser Nanofabrication, Hengky Chandrahalim, Qiushu Chen, Ali A. Said, Mark Dugan, Xudong Fan

Faculty Publications

We designed, fabricated, and characterized a monolithically integrated optofluidic ring resonator laser that is mechanically, thermally, and chemically robust. The entire device, including the ring resonator channel and sample delivery microfluidics, was created in a block of fused-silica glass using a 3-dimensional femtosecond laser writing process. The gain medium, composed of Rhodamine 6G (R6G) dissolved in quinoline, was flowed through the ring resonator. Lasing was achieved at a pump threshold of approximately 15 μJ/mm². Detailed analysis shows that the Q-factor of the optofluidic ring resonator is 3.3 × 10⁴, which is limited by both solvent …

Sulfur Vacancies In Photorefractive Sn2P2S6 Crystals, Eric M. Golden, Sergey A. Basun, A. A. Grabar, I. M. Stoika, Nancy C. Giles, D. R. Evans, Larry E. Halliburton

Faculty Publications

A photoinduced electron paramagnetic resonance (EPR) spectrum in single crystals of Sn2P2S6 (SPS) is assigned to an electron trapped at a sulfur vacancy. These vacancies are unintentionally present in undoped SPS crystals and are expected to play an important role in the photorefractive behavior of the material. Nonparamagnetic sulfur vacancies are formed during the initial growth of the crystal. Subsequent illumination below 100 K with 442 nm laser light easily converts these vacancies to EPR-active defects. The resulting S = 1/2 spectrum shows well-resolved and nearly isotropic hyperfine interactions with two P ions and two Sn ions. Partially resolved interactions …

Performance Analysis Of A Hybrid Raman Optical Parametric Amplifier In The O- And E-Bands For Cwdm Pons, Sasanthi Peiris, Nicolas Madamopoulos, Neophytos A. Antoniades, Dwight Richards, Roger Dorsinville

Publications and Research

We describe a hybrid Raman-optical parametric amplifier (HROPA) operating at the O- and E-bands and designed for coarse wavelength division multiplexed (CWDM) passive optical networks (PONs). We present the mathematical model and simulation results for the optimization of this HROPA design. Our analysis shows that separating the two amplification processes allows for optimization of each one separately, e.g., proper selection of pump optical powers and wavelengths to achieve maximum gain bandwidth and low gain ripple. Furthermore, we show that the proper design of optical filters incorporated in the HROPA architecture can suppress idlers generated during the OPA process, as well …

Investigation Of The Dynamics Of Photocarriers During Photoelectrochemical Water Splitting By Combination Of Photoelectrochemistry And Transient Absorption Spectroscopy, Wen-Hua Leng

Journal of Electrochemistry

Semiconductor photoelectrochemical hydrogen production is an important and promising technology for utilizing solar energy. The efficiency of hydrogen production depends on the efficiencies of separation and transport of photo-generated carriers. A deep understanding of the behavior of these processes has guiding significance for designing efficient solar hydrogen device. photoelectrochemical and transient absorption spectroscopy methods are powerful tool for studying the microscopic dynamics and mechanism of photocatalytic reaction. This review describes the part of the latest results of the author regarding the semiconductor photoelectrochemical hydrogen production obtained by these methods,and the problems and future research priorities in this field are proposed.