Engineering Commons^™

Evolution Characteristics Of Perovskite Solar Cells In Air And Vacuum Environments, Xiaohui Wang, Hojjatollah Sarvari, Hongmei Dang, Zhi Chen, Vijay P. Singh

Electrical and Computer Engineering Faculty Publications

Solid state hybrid organometal halide perovskite solar cells have become the research hotspots recently. We prepared perovskite solar cells by the simple two-step method in the ambient condition. The solar cell samples were kept in air and vacuum environments, respectively. J_sc shows good stability in vacuum for up to 27 days, while it drops a lot in air. There is a remarkable promotion of FF for the air-stored samples compared that of the vacuum-stored samples. Changes in V_oc of vacuum-stored and airstored samples exhibited a similar behavior, both showing a slight increase. We believe the moisture in air …

Load Model Verification, Validation And Calibration Framework By Statistical Analysis On Field Data, Xiangqing Jiao, Yuan Liao, Thai Nguyen

Electrical and Computer Engineering Faculty Publications

Accurate load models are critical for power system analysis and operation. A large amount of research work has been done on load modeling. Most of the existing research focuses on developing load models, while little has been done on developing formal load model verification and validation (V&V) methodologies or procedures. Most of the existing load model validation is based on qualitative rather than quantitative analysis. In addition, not all aspects of model V&V problem have been addressed by the existing approaches. To complement the existing methods, this paper proposes a novel load model verification and validation framework that can systematically …

Improving The Performance And Stability Of Flexible Pressure Sensors With An Air Gap Structure, Xiongbang Wei, Lun Xiao, Wen Huang, Jiaxuan Liao, Zhi David Chen

Electrical and Computer Engineering Faculty Publications

A highly sensitive flexible resistive pressure sensor based on an air gap structure was presented. The flexible pressure sensor consists of two face to face polydimethylsiloxane (PDMS) films covered with carbon nanotubes (CNTs). The pressure sensor with a 230 μm thickness air gap has relatively high sensitivity (58.9 kPa⁻¹ in the range of 1–5 Pa, 0.66 kPa⁻¹ in the range of 5–100 Pa), low detectable pressure limit (1 Pa), and a short response time (less than 1 s). The test results showed that the pressure sensor with an appropriate air gap has excellent pressure sensitive performance and application …

Optical And Electronic Properties Of Femtosecond Laser-Induced Sulfur-Hyperdoped Silicon N+/P Photodiodes, Ting Zhang, Bohan Liu, Waseem Ahmad, Yaoyu Xuan, Xiangxiao Ying, Zhijun Liu, Zhi David Chen, Shibin Li

Electrical and Computer Engineering Faculty Publications

Impurity-mediated near-infrared (NIR) photoresponse in silicon is of great interest for photovoltaics and photodetectors. In this paper, we have fabricated a series of n⁺/p photodetectors with hyperdoped silicon prepared by ion-implantation and femtosecond pulsed laser. These devices showed a remarkable enhancement on absorption and photoresponse at NIR wavelengths. The device fabricated with implantation dose of 10¹⁴ ions/cm² has exhibited the best performance. The proposed method offers an approach to fabricate low-cost broadband silicon-based photodetectors.

Pulsed Laser Beam Welding Of Pd43Cu27Ni10P20 Bulk Metallic Glass, Ling Shao, Amit Datye, Jiankang Huang, Jittisa Ketkaew, Sung Woo Sohn, Shaofan Zhao, Sujun Wu, Yuming Zhang, Udo D. Schwarz, Jan Schroers

Electrical and Computer Engineering Faculty Publications

We used pulsed laser beam welding method to join Pd₄₃Cu₂₇Ni₁₀P₂₀ (at.%) bulk metallic glass and characterized the properties of the joint. Fusion zone and heat-affected zone in the weld joint can be maintained completely amorphous as confirmed by X-ray diffraction and differential scanning calorimetry. No visible defects were observed in the weld joint. Nanoindentation and bend tests were carried out to determine the mechanical properties of the weld joint. Fusion zone and heat-affected zone exhibit very similar elastic moduli and hardness when compared to the base material, and the weld joint shows high …

Realizing Full Coverage Of Stable Perovskite Film By Modified Anti-Solvent Process, Long Ji, Ting Zhang, Yafei Wang, Peng Zhang, Detao Liu, Zhi David Chen, Shibin Li

Electrical and Computer Engineering Faculty Publications

Lead-free solution-processed solid-state photovoltaic devices based on formamidinium tin triiodide (FASnI₃) and cesium tin triiodide (CsSnI₃) perovskite semiconductor as the light harvester are reported. In this letter, we used solvent engineering and anti-solvent dripping method to fabricate perovskite films. SnCl₂ was used as an inhibitor of Sn⁴⁺ in FASnI₃ precursor solution. We obtained the best films under the function of toluene or chlorobenzene in anti-solvent dripping method and monitored the oxidation of FASnI₃ films in air. We chose SnF₂ as an additive of CsSnI₃ precursor solution to prevent the oxidation …

Enhanced Performance Of Planar Perovskite Solar Cells Using Low-Temperature Solution-Processed Al-Doped Sno2 As Electron Transport Layers, Hao Chen, Detao Liu, Yafei Wang, Chenyun Wang, Ting Zhang, Peng Zhang, Hojjatollah Sarvari, Zhi Chen, Shibin Li

Electrical and Computer Engineering Faculty Publications

Lead halide perovskite solar cells (PSCs) appear to be the ideal future candidate for photovoltaic applications owing to the rapid development in recent years. The electron transport layers (ETLs) prepared by low-temperature process are essential for widespread implementation and large-scale commercialization of PSCs. Here, we report an effective approach for producing planar PSCs with Al³⁺ doped SnO₂ ETLs prepared by using a low-temperature solution-processed method. The Al dopant in SnO₂ enhanced the charge transport behavior of planar PSCs and increased the current density of the devices, compared with the undoped SnO₂ ETLs. Moreover, the enhanced electrical …

Electronic Properties Of A New All-Inorganic Perovskite Tlpbi3 Simulated By The First Principles, Zhao Liu, Ting Zhang, Yafei Wang, Chenyun Wang, Peng Zhang, Hojjatollah Sarvari, Zhi Chen, Shibin Li

Electrical and Computer Engineering Faculty Publications

All-inorganic perovskites have been recognized as promising photovoltaic materials. We simulated the perovskite material of TlPbI₃ using ab initio electronic structure calculations. The band gap of 1.33 eV is extremely close to the theoretical optimum value. Compared TlPbI₃ with CsPbI₃, the total energy (−3980 eV) of the former is much lower than the latter. The partial density of states (PDOS) of TlPbI₃ shows that a strong bond exists between Tl and I, resulting in the lower total energy and more stable existence than CsPbI₃.

Focused Electron Beam Induced Deposition Of Copper With High Resolution And Purity From Aqueous Solutions, Samaneh Esfandiarpour, Lindsay Boehme, J. Todd Hastings

Electrical and Computer Engineering Faculty Publications

Electron-beam induced deposition of high-purity copper nanostructures is desirable for nanoscale rapid prototyping, interconnection of chemically synthesized structures, and integrated circuit editing. However, metalorganic, gas-phase precursors for copper introduce high levels of carbon contamination. Here we demonstrate electron beam induced deposition of high-purity copper nanostructures from aqueous solutions of copper sulfate. The addition of sulfuric acid eliminates oxygen contamination from the deposit and produces a deposit with ~95 at% copper. The addition of sodium dodecyl sulfate (SDS), Triton X-100, or polyethylene glycole (PEG) improves pattern resolution and controls deposit morphology but leads to slightly reduced purity. High resolution nested lines …

Using A Respiratory Navigator Significantly Reduces Variability When Quantifying Left Ventricular Torsion With Cardiovascular Magnetic Resonance, Sean M. Hamlet, Christopher M. Haggerty, Jonathan D. Suever, Gregory J. Wehner, Kristin N. Andres, David K. Powell, Richard J. Charnigo, Brandon K. Fornwalt

Electrical and Computer Engineering Faculty Publications

Background: Left ventricular (LV) torsion is an important indicator of cardiac function that is limited by high inter-test variability (50% of the mean value). We hypothesized that this high inter-test variability is partly due to inconsistent breath-hold positions during serial image acquisitions, which could be significantly improved by using a respiratory navigator for cardiovascular magnetic resonance (CMR) based quantification of LV torsion.

Methods: We assessed respiratory-related variability in measured LV torsion with two distinct experimental protocols. First, 17 volunteers were recruited for CMR with cine displacement encoding with stimulated echoes (DENSE) in which a respiratory navigator was used to measure …

Side Information In Coded Aperture Compressive Spectral Imaging, Laura Galvis, Henry Arguello, Daniel L. Lau, Gonzalo R. Arce

Electrical and Computer Engineering Faculty Publications

Coded aperture compressive spectral imagers sense a three-dimensional cube by using two-dimensional projections of the coded and spectrally dispersed source. These imagers systems often rely on FPA detectors, SLMs, micromirror devices (DMDs), and dispersive elements. The use of the DMDs to implement the coded apertures facilitates the capture of multiple projections, each admitting a different coded aperture pattern. The DMD allows not only to collect the sufficient number of measurements for spectrally rich scenes or very detailed spatial scenes but to design the spatial structure of the coded apertures to maximize the information content on the compressive measurements. Although sparsity …

A Novel Composite Hydrogen Sensor Based On Pd Nanoclusters/Tio2 Nanotube Arrays, X. B. Wei, X. H. Yang, T. Wu, H. Y. Pang, G. D. Lv, S. H. Wu, S. B. Li, Zhi Chen

Electrical and Computer Engineering Faculty Publications

A novel composite hydrogen sensor, consisting of Pd nanoclusters/TiO₂ nanotube arrays, was fabricated and evaluated at room temperature. The Pd nanoclusters layer was deposited on top surface of the nanotube arrays by using a direct current (DC) magnetron sputtering method. Resistive response of the composite sensors to 0.5% hydrogen was measured. Experimental results indicated that the Pd nanoclusters can quickly and continually form or break multiple passages by absorbing or desorbing hydrogen, so that the composite hydrogen sensors have promising hydrogen sensitivity at room temperature.

A Multi-Institutional Approach To Delivering Shared Curricula For Developing A Next-Generation Energy Workforce, Lawrence E. Holloway, Zhihua Qu, Margaret J. Mohr-Schroeder, Juan Carlos Balda, Andrea Benigni, Donald G. Colliver, Paul A. Dolloff, Roger A. Dougal, M. Omar Faruque, Zongming Fei, Yuan Liao, Roy A. Mccann, R. Mark Nelms, Vijay P. Singh, Azadeh Vosoughi, Qun Zhou

Electrical and Computer Engineering Faculty Publications

In this paper, we consider collaborative power systems education through the FEEDER consortium. To increase students' access to power engineering educational content, the consortium of seven universities was formed. A framework is presented to characterize different collaborative education activities among the universities. Three of these approaches of collaborative educational activities are presented and discussed. These include 1) cross-institutional blended courses (“MS-MD”); 2) cross-institutional distance courses (“SS-MD”); and 3) single-site special experiential courses and concentrated on-site programs available to students across consortium institutions (“MS-SD”). This paper presents the advantages and disadvantages of each approach.

Efficient Planar Heterojunction Perovskite Solar Cells With Li-Doped Compact Tio2 Layer, Detao Liu, Shibin Li, Peng Zhang, Yafei Wang, Rui Zhang, Hojjatollah Sarvari, Feng Wang, Jiang Wu, Zhiming Wang, Zhi Chen

Electrical and Computer Engineering Faculty Publications

Perovskite solar cells (PSCs) have been developed rapidly in recent time, and efficient planar PSCs are regarded as the most promising alternative to the Si solar cells. In this study, we demonstrated that Li-doping of compact TiO₂ can reduce the density of electron traps and increase the conductivity of the electron transport layer (ETL) of PSCs. Due to the improved electronic property of ETL, the Li-doped compact TiO₂ based planar heterojunction PSCs exhibit negligible hysteretic J-V behavior. Comparing with the undoped compact TiO₂ based PSCs, the power conversion efficiency (PCE) of the Li-doped compact TiO₂ film …