Transparent conductive adhesives (TCAs) can enable conductivity between two substrates, which is useful for a wide range of electronic devices. Here, we have developed a TCA composed of a ...polymer–particle blend with ethylene-vinyl acetate as the transparent adhesive and metal-coated flexible poly(methyl methacrylate) microspheres as the conductive particles that can provide conductivity and adhesion regardless of the surface texture. This TCA layer was designed to be nearly transparent, conductive in only the out-of-plane direction, and of practical adhesive strength to hold the substrates together. The series resistance was measured at 0.3 and 0.8 Ω cm2 for 8 and 0.2% particle coverage, respectively, while remaining over 92% was transparent in both cases. For applications in photovoltaic devices, such as mechanically stacked multijunction III–V/Si cells, a TCA with 1% particle coverage will have less than 0.5% power loss due to the resistance and less than 1% shading loss to the bottom cell.
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IJS, KILJ, NUK, PNG, UL, UM
43.
Growth of amorphous and epitaxial ZnSiP2-Si alloys on Si Martinez, Aaron D; Miller, Elisa M; Norman, Andrew G ...
Journal of materials chemistry. C, Materials for optical and electronic devices,
2018, Volume:
6, Issue:
11
Journal Article
Peer reviewed
Open access
ZnSiP
2
is a wide band gap material that is lattice matched with Si, offering the potential for Si-based optoelectronic materials and devices, including multijunction photovoltaics. We present a ...carbon-free chemical vapor deposition process for the growth of both epitaxial and amorphous thin films of ZnSiP
2
-Si alloys with tunable Si content on Si substrates. Si alloy content is widely tunable across the full composition space in amorphous films. Optical absorption of these films reveals relatively little variation with Si content, despite the fact that ZnSiP
2
has a much wider band gap of 2.1 eV. Post-growth crystallization of Si-rich films resulted in epitaxial alignment, as measured by X-ray diffraction and transmission electron microscopy. These films have an optical absorption onset near 1.1 eV, suggesting the possibility of band gap tuning with Si content in crystalline films. The optical absorption is comparably strong to pure ZnSiP
2
, suggesting a more direct transition than in pure Si.
ZnSiP
2
is a wide band gap material lattice matched with Si, with potential for Si-based optoelectronics. Here, amorphous ZnSiP
2
-Si alloys are grown with tunable composition. Films with Si-rich compositions can be crystallized into epitaxial films.
The discovery of new materials by coupling high-throughput synthesis with computational screening is being increasingly adopted. However, thus far, phosphides have been largely overlooked for both ...computational screening and high-throughput synthesis. In this paper, we report on the use of a high-throughput synthesis technique, reactive combinatorial co-sputtering with PH3, to deposit ZnGeP2 thin films. We grew amorphous films over a wide range of compositions and found an upper limit in growth temperature determined by Zn and P volatility. We found that depositing in a Ge-limited regime could be utilized to slow the growth rate to compensate for the desorption of the Zn and P. Crystalline films were achieved by depositing films at higher temperatures in this Ge-limited regime with a reduced deposition rate. X-ray diffraction revealed that the films had crystallized in the zinc blende, cation-disordered structure. The crystalline films exhibited optical absorption energy threshold values ranging from 0.8 to 1.3 eV. Increased Ge content was found in films that exhibited a decreased absorption onset energy. Native defect calculations were used to gain an understanding of the off-stoichiometry seen in these films. This work provides the first high-throughput investigation of ZnGeP2, demonstrating the ability to grow amorphous and cation disordered ZnGeP2 over a wide range of compositions with varying optical properties.
The Front Cover illustrates a TCE sheet, where the rainbow is the light reaching the photoelectrode, the spheres are the conductive pathway through the polymer matrix to the electrochemical ...interface, and the methyl viologen redox couple is reduced in the solution. Cover design by Talysa Klein (www.tk2.design). More information can be found in the Research Article by G. A. Rome et al.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Integrating III-Vs onto Si is a promising route toward tandem photovoltaics and cost mitigation of III-V substrates. While many III-V/Si photovoltaic integration approaches have been studied, ...epitaxial growth on Si allows for fewer processing steps compared to other approaches. However, current epitaxial pathways utilize expensive techniques, such as thermal cycle annealing or thick buffer layers to control defect densities, undermining the low-cost goal of integrating III-Vs with Si. Here, we present single-junction GaAs solar cells grown directly on Si using selective area growth as an alternative low-cost technique to control material quality with a much thinner buffer. We demonstrate a 10.4%-efficient GaAs device grown on a V-grooved Si substrate, which achieved an antiphase domain-free III-V/Si interface and a threading dislocation density of 2 × 10 7 cm -2 , despite the lack of a graded buffer. We compare this growth on V-grooved Si to solar cells grown on polished Si with and without a patterned silica buffer layer, which demonstrate efficiencies of 6.5% and 6.8%, respectively; the polished Si was patterned using nanoimprint lithography, which is a low-cost patterning technique compatible with III-V selective area growth. Cracking is found to be a critical challenge that hinders solar cell performance and is exacerbated by the V-grooved Si surface topography. The results in this paper provide a promising pathway toward high-efficiency, low-cost III-V/Si tandem photovoltaics.
Tandem or multijunction solar cells are able to convert sunlight to electricity with greater efficiency than single junction solar cells by splitting the solar spectrum across sub-cells with ...different bandgaps. With the efficiencies of many common single-junction solar cell materials leveling off near their theoretical efficiency limits, there is renewed interest in applying this approach. However, there is ongoing debate as to the best approach for interconnecting sub-cells in series, or whether it is preferable to operate them independently. In this paper, we provide the first experimental demonstration of a tandem cell architecture with three terminals: one on top of the tandem cell, and two beneath it, in interdigitated back contact configuration. The two cells are interconnected with a transparent conductive adhesive, which is compatible with rough surfaces and exhibits negligible series resistance. Combining GaInP and Si sub-cells in this manner allows us to achieve a GaInP/Si tandem cell with a two-terminal efficiency of 26.4 ± 1.0%. We then show that utilizing all three terminals results in an efficiency boost of 0.9 ± 0.2%, to an efficiency of 27.3 ± 1.0%, and discuss the operation of the cell and its two interacting circuits.
Three-terminal tandem solar cell with conductive adhesive interconnect and back-contacted bottom cell delivers 27.3% efficiency.
The pursuit of ever-higher solar cell efficiencies has focused heavily on multijunction technologies. In tandem cells, subcells are typically either contacted via two terminals (2T) or four terminals ...(4T). Simulations show that the less-common three-terminal (3T) design may be comparable to 4T tandem cells in its compatibility with a range of materials, operating conditions, and methods for subcell integration, yet the 3T design circumvents shading losses of the 4T intermediate conductive layers. This study analyzes the performance of two superstrate 3T III-V-on-Si (III-V//Si) tandem cells: One has slightly greater current contribution from the Si bottom cell (GaInP//Si) and the other has substantially greater current contribution from the GaAs top cell (GaAs//Si). Our results show that both tandem cells exhibit the same efficiency (21.3%), thereby demonstrating that the third terminal allows for flexibility in the selection of the top cell material, similar to the 4T design.
Display omitted
•New 3-terminal tandem superstrate design provides mechanical support to both subcells•Third terminal enables extraction of surplus photocurrent from mismatched subcells•Data show that a third terminal allows for flexibility in top cell material selection
Materials science; Electronic materials; Energy materials
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
II-IV-V
2
materials, ternary analogs to III-V materials, are emerging for their potential applications in devices such as LEDs and solar cells. Controlling cation ordering in II-IV-V
2
materials ...offers the potential to tune properties at nearly fixed compositions and lattice parameters. While tuning properties at a fixed lattice constant through ordering has the potential to be a powerful tool used in device fabrication, cation ordering also creates challenges with characterization and quantification of ordering. In this work, we investigate two different methods to quantify cation ordering in ZnGeP
2
thin films: a stretching parameter calculated from lattice constants
, and an order parameter determined from the cation site occupancies (
S
). We use high resolution X-ray diffraction (HRXRD) to determine
and resonant energy X-ray diffraction (REXD) to extract
S
. REXD is critical to distinguish between elements with similar
Z
-number (
e.g.
Zn and Ge). We found that samples with a
corresponding to the ordered chalcopyrite structure had only partially ordered
S
values. The optical absorption onset for these films occurred at lower energy than expected for fully ordered ZnGeP
2
, indicating that
S
is a more accurate descriptor of cation order than the stretching parameter. Since disorder is complex and can occur on many length scales, metrics for quantifying disorder should be chosen that most accurately reflect the physical properties of interest.
Resonant energy X-ray diffraction was used to quantify cation site ordering in ZnGeP
2
thin films.
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