A5073865533- Chalcogenide Semiconductor Thin Films
- Quantum Dots Synthesis And Properties
- Electron and X-Ray Spectroscopy Techniques
- Copper-based nanomaterials and applications
- Machine Learning in Materials Science
- Semiconductor materials and interfaces
- Advanced Semiconductor Detectors and Materials
- ZnO doping and properties
- Advanced Electron Microscopy Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Ga2O3 and related materials
- Gas Sensing Nanomaterials and Sensors
- Integrated Circuits and Semiconductor Failure Analysis
- Electronic and Structural Properties of Oxides
- Silicon and Solar Cell Technologies
Arizona State University
2018-2023
First Solar (United States)
2022
Argonne National Laboratory
2022
Purdue University West Lafayette
2022
University of Oxford
1998-2002
High resolution valence- and core-level photoemission spectra of undoped 3% Sb-doped ${\mathrm{SnO}}_{2}$ are presented. Conduction-band occupation due to Sb doping in leads a shift valence-band features high binding energy. However, the is less than width occupied part conduction band. This attributed shrinkage bulk band gap with doping, arising from an attractive dopant electron interaction screening Coulomb repulsion between valence electrons. Core-level provide evidence for strong by gas...
Copper has been used as a p-type dopant in cadmium telluride (CdTe) for decades. However, the density of Cu atoms finished device is much higher than that holes, which means most are not activated acceptors during incorporation. Furthermore, studies have demonstrated distribution copper (Cu) across highly inhomogeneous, with reports citing substitution on Cd sites and segregation to grain boundaries. Fast diffusion along these boundaries accumulation at CdTe/CdS interface also observed...
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Nano-X-ray fluorescence microscopy is used to correlate elemental inhomogeneity device performance measured through X-ray beam induced current (XBIC). Unsupervised machine learning techniques can be useful in the processing and correlation of XRF/XBIC data. A case study using CuInSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> solar cells treated with Ag-alloying KF-post- deposition treatment (PDT) presented. The implementation...
For decades, copper has been used to improve the performance of cadmium telluride thin film solar cells. However, it also shown be main cause metastability in CdTe. Recently a low activation energy reported for thermal diffusion Cu CdTe explaining ease motion that under moderate temperatures. The community consensus is segregates absorber grain boundaries, where it's either beneficial or detrimental device depending on its concentration. Using nanoscale X-ray micrsocopy and two-dimensional...
For decades, copper has been introduced in CdTe devices to improve overall performance (open circuit voltage, fill factor, and series resistance). While multiple articles have reported on Cu-based defects, very little is known about how the local structure around atom affects electrical performance. Using X-ray Absorption Near Edge Structure (XANES) coupled with microscopy we investigate good poor performing region Cu-doped devices. Our XANES theoretical standards by FEFF9 suggest that CU...
CuInSe2 (CIS) has been proposed as an attractive bottom cell candidate in tandem solar cells. However, to justify the coupling with high-performance top cells (e.g., perovskites, GaAs), significant work on improving efficiency is required. To this extent, several authors have demonstrated benefits of alkali post-deposition treatments (PDT) increase device open-circuit voltage (Voc) CIS and how Ag alloying—(Ag,Cu)InSe2 (ACIS)—reduces defect density enhances current collection devices. Herein,...
It is widely accepted that micro- and nanoscale inhomogeneities govern the performance of many thin-film solar cell absorbers. These yield material properties (e.g., composition, structure, charge collection) are challenging to correlate across length scales measurement modalities. The challenge compounded if a correlation sought during device operation or in conditions mimic aging under particular stressors heat electrical bias). Correlative approaches, particularly those based on...
X-ray absorption spectroscopy (XAS) has been shown to be a powerful tool unravel the chemical environment of given atom within matrix. When used in correlative microscopy approaches, XAS allows one probe with nanoscale precision regions particular interest an absorber. Herein, we use near edge structure (XANES) evaluate Cu atoms CdTe solar cell. The reconstruction XANES spectra from XRF maps have unfolded 2D structures. In this work, found that most exist <inf...
The origin of metastability in Cu(In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> )Se xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> solar cells has long be a topic study and debate. drop device performance after light soaking been attributed to changes the V xmlns:xlink="http://www.w3.org/1999/xlink">Se</sub> -V xmlns:xlink="http://www.w3.org/1999/xlink">Cu</sub> defect pair...
The selection of arsenic as a dopant has been an integral part achieving high performing, 20.8%, polycrystalline CdTe solar cells. Although significantly improved the long-term performance cells and p-type doping levels reached inside absorber, activation ratio remains quite low, ~1%. Understanding origins this would aid in further bettering device performance. Herein, devices two different but identical concentration are studied using nanoscale correlative X-ray microscopy cross-section....
X-ray microscopy is a powerful tool to study defects in solar cells as it allows correlate pixel-by-pixel the local environment of selected atoms and nanoscale electrical performance. In this work, we used absorption near edge structures (XANES) induced current (XBIC) track Se structures, particularly changes Se-Cd bond lengths, across CdSexTe(1-x) absorber layer, contrasts areas with high low Even though all experimental K-edge XANES clearly show signature CdSexTe(1-x), there are spectral...
Copper is a traditional dopant for many types of polycrystalline thin-film CdTe photovoltaic devices. However, Cu can easily distribute through the depth and breadth device, segregating at interfaces or grain boundaries leading to metastability device. Directly correlating Cu-related defect species local (i.e. nanoscale) charge transport in devices remains challenging due relatively low concentrations layer. Using nanoscale X-ray microscopy, we simultaneously probe both elemental copper...