A5062515405- Chalcogenide Semiconductor Thin Films
- Silicon and Solar Cell Technologies
- Quantum Dots Synthesis And Properties
- Thin-Film Transistor Technologies
- Semiconductor materials and interfaces
- Integrated Circuits and Semiconductor Failure Analysis
- Advanced Semiconductor Detectors and Materials
- solar cell performance optimization
- Semiconductor Quantum Structures and Devices
- Semiconductor materials and devices
- Silicon Nanostructures and Photoluminescence
- Nanowire Synthesis and Applications
- Copper-based nanomaterials and applications
- Advanced Battery Materials and Technologies
- Advancements in Battery Materials
- Perovskite Materials and Applications
- Photovoltaic System Optimization Techniques
- Thermal Radiation and Cooling Technologies
- Advanced Battery Technologies Research
- GaN-based semiconductor devices and materials
- ZnO doping and properties
- Advanced Thermodynamics and Statistical Mechanics
- Conducting polymers and applications
- Metal and Thin Film Mechanics
- Advancements in Semiconductor Devices and Circuit Design
National Renewable Energy Laboratory
2016-2025
Colorado School of Mines
2011-2023
First Solar (United States)
2022
University of California, Berkeley
2019
Electron-beam-induced damages in methylammonium lead triiodide (MAPbI3) perovskite thin films were studied by cathodoluminescence (CL) spectroscopy. We find that high-energy electron beams can significantly alter properties through two distinct mechanisms: (1) defect formation caused irradiation damage and (2) phase transformation induced electron-beam heating. The former mechanism causes quenching broadening of the excitonic peaks CL spectra, whereas latter results new with higher emission...
We conducted cathodoluminescence (CL) spectrum imaging and electron backscatter diffraction on the same microscopic areas of CdTe thin films to correlate grain-boundary (GB) recombination by GB “type.” examined misorientation-based types, including coincident site lattice (CSL) Σ = 3, other-CSL (Σ 5–49), general GBs > 49), which make up ∼47%–48%, ∼6%–8%, ∼44%–47%, respectively, length at film back surfaces. Statistically averaged CL total intensities were calculated for each type from...
A systematic study of the role insulator layer on rectification performance in metal–insulator–metal structures is reported. Four different MIM systems with Nb/Pt metal pairs and Nb2O5, TiO2, Al2O3, MgO as candidates are investigated based an empirical hypothesis. As per hypothesis experimental verification, several prospective such Sm/ZrO2/Pt Hf/TiO2/Pt identified a materials-space constructed.
Thin-film solar cells based on polycrystalline Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film can reach such high efficiencies despite containing a density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this paper, we review our atomistic theoretical understanding the physics in CIGS absorbers. We show intrinsic GBs...
Photovoltaic conversion efficiencies of 32.6 ± 1.4% under the AM1.5 G173 global spectrum, and 35.5% 1.2% at 38-suns concentration direct are demonstrated for a monolithic, dual-junction 1.7/1.1 eV solar cell. The tandem cell consists 1.7 GaInAsP top-junction grown lattice-matched to GaAs substrate, followed by metamorphic 1.1 GaInAs junction on transparent, compositionally graded AlGaInAs buffer. This bandgap combination is much closer optimum offers headroom absolute 3% improvement in...
We investigated potential-induced degradation (PID) in silicon mini-modules that were subjected to accelerated stressing induce PID conditions. Shunted areas on the cells identified with photoluminescence and dark lock-in thermography (DLIT) imaging. The identical shunted then analyzed via time-of-flight secondary-ion mass spectrometry (TOFSIMS) imaging, 3-D tomography, high-resolution transmission electron microscopy. TOF-SIMS imaging indicates a high concentration of sodium areas,...
All-solid lithium batteries are an attractive next-generation technology that use ion-conducting solids such as β-Li3PS4 (LPS) to enable of a metal anode, which increases theoretical capacity and widens the stable voltage window over traditional lithium-ion systems. These ion-conductive also provide increased safety by replacing flammable liquid electrolytes. Although solid-state electrolytes significantly more dendrite-resistant than electrolytes, anodes in all-solid systems may...
We report on the microscopic structure of SiOx layer and transport mechanism in polycrystalline Si (poly-Si) passivated contacts, which enable high-efficiency crystalline (c-Si) solar cells. Using electron beam induced current (EBIC) measurements, we accurately map nanoscale conduction-enabling pinholes 2.2 nm thick layers a poly-Si/SiOx/c-Si stack. These conduction enabling appear as bright spots EBIC maps due to carrier collection limitations introduced by insulating layer. Performing...
Fluctuations refer to inhomogeneity in the distribution of donors and acceptors at nanometer scale occur many compound solar cell materials such as Cu(In,Ga)Se2, Cu2ZnSn(S,Se)4, CdSexTe1−x. In this work, numerical simulations show that these fluctuations produce not only electrostatic potential variation, but also, local changes carrier density effective bandgap. For a CdSexTe1−x absorber doped with arsenic, cathodoluminescence data within single grains demonstrate how donor acceptor...
Abstract Radical reduction of III–V device costs requires a multifaceted approach attacking both growth and substrate costs. Implementing removal reuse provides an opportunity for cost reduction. Controlled spalling allows thin devices from the expensive substrate; however, fracture‐based process currently generates surfaces with significant morphological changes compared to polished wafers. 49 single junction are fabricated across spalled surface full 50 mm germanium wafers without...
Abstract Inverted metamorphic Ga 0.3 In 0.7 As photovoltaic converters with sub‐0.60 eV bandgaps grown on InP and GaAs are presented. Threading dislocation densities 1.3 ± 0.6 × 10 6 8.9 1.7 cm −2 GaAs, respectively. The devices generate open‐circuit voltages of 0.386 0.383 V, respectively, under irradiance producing a short‐circuit current density ≈10 A , yielding bandgap‐voltage offsets 0.20 0.21 V. Power broadband reflectance measurements used to estimate thermophotovoltaic (TPV)...
High-efficiency crystalline silicon (Si) solar cells require textured surfaces for efficient light trapping. However, passivation of a surface to reduce carrier recombination is difficult. Here, we relate the electrical properties fabricated on KOH-etched, random pyramidal-textured Si nanostructure passivated contact and morphology. The effects both microscopic pyramidal morphology nanoscale roughness contacts consisting polycrystalline (poly-Si) deposited top an ultrathin, 1.5–2.2 nm, SiOx...
For decades, polycrystalline CdTe thin films for solar applications have been restricted to grain sizes of microns or less whereas other semiconductors such as silicon and perovskites produced devices with grains ranging from than a micron more 1 mm. Because the lifetimes in as-deposited are typically limited few hundred picoseconds, CdCl2 treatment is generally used improve lifetime; but this may limit achievable hole density by compensation. Here, we establish methods produce hundreds...
Abstract Replacing the liquid electrolyte in lithium batteries with solid‐state ion conductor is promising for next‐generation energy storage that safe and has high density. Here, nanometer‐resolution ionic electronic transport imaging of Li 3 PS 4 (LPS), a (SSE), reported. This nm resolution achieved by using logarithm‐scale current amplifier enhances sensitivity to fA range. Large fluctuations current—one two orders magnitude on LPS region polymer/LPS bulk hybrid SSE—that must be mitigated...
Abstract Alkali metal doping and grain boundaries (GB) have been at the center of attention within Cu(In,Ga)(S,Se) 2 photovoltaics community for years. This study provides first experimental evidence that GB sodium‐doped CuInSe thin films may undertake reversible oxidation even room temperature, whereas undoped not. The findings are corroborated by cathodoluminescence imaging, secondary ion mass spectrometry, Kelvin probe force microscopy on air‐exposed subsequently subject to vacuum. A...
A set of neighboring multicrystalline silicon wafers has been processed through different steps solar cell manufacturing and then images were collected for characterization. The imaging techniques include band-to-band photoluminescence (PL), defect-band or subbandgap PL (subPL), dark lock-in thermography (DLIT). Defect regions can be tracked from as-cut throughout processing to the finished cells. cell's defect detected by correlate well diffusion length quantum efficiency maps. most...
We determine the grain-boundary (GB) recombination velocity, SGB, and grain-interior (GI) lifetime, τGI, parameters in superstrate CdS/CdTe thin-film solar cell technology by combining cathodoluminescence (CL) spectrum imaging time-resolved photoluminescence (TRPL) measurements. consider critical device formation stages, including after CdTe deposition, CdCl2 treatment, Cu diffusion. CL image analysis methods extract GB GI intensities grain size for hundreds of grains per sample....
Abstract Crystallographic structures, optoelectronic properties, and nanoscale surface morphologies of ex situ phosphorus‐doped polycrystalline silicon (poly‐Si)/SiO x passivating contacts, formed by different deposition methods (sputtering, plasma‐enhanced chemical vapour [PECVD], low‐pressure [LPCVD]), are investigated compared. Across all these technologies, we noted the same trend: higher diffusion temperatures yield films that more crystalline but have rougher due to bigger crystal...
We investigate strategies to suppress phase separation and reduce threading dislocation density (TDD) in AlGaInAs compositionally graded buffers (CGBs) that span the lattice constant range from GaAs InP. Combining results high resolution x-ray diffraction, cathodoluminescence, transmission electron microscopy, photovoltaic device measurements, we correlate choices of epitaxial growth conditions with defect structure CGBs subsequent performance. Both use substrates misorientation off (100)...