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  1. Unveiling the Role of In Situ Al2O3 Passivation in Molecular-Ink-Processed CuIn(S,Se)2 Photovoltaics

    Septina, Wilman ; Paranhos Lopes, Jade ; Muzzillo, Christopher P. ; ... - ACS Applied Energy Materials
    Here, we report on the optimization of in situ passivation of ink-based CuIn(S,Se)2 thin-film solar cells via controlled incorporation of Al2O3 in CuIn(S,Se)2 films by the addition of Al(NO3)3 to the molecular ink precursor. For this purpose, the Al/(Al + In) (AAI) metal ratio was varied from 0.05 to 0.30. We observe that the efficiency of the cells made of Al2O3-incorporated CuIn(S,Se)2 is consistently higher than those without Al2O3, especially due to an improvement in open-circuit voltage (VOC) and fill factor (FF), for all tested AAI ratios. With an AAI of 0.05, a maximum efficiency of 11.2% and an averagemore » efficiency of 8.5% (measured across 18 cells) was achieved, compared to 8.5% maximum efficiency and 6.5% average efficiency for Al-free CuIn(S,Se)2. Furthermore, we find that cells made of Al2O3-incorporated CuIn(S,Se)2 with an AAI of 0.2 show a narrow distribution in the photovoltaic performance, indicating higher reproducibility and higher FF. Energy-dispersive X-ray spectroscopy shows that, at AAI = 0.2, Al2O3 is distributed more homogeneously at the surface of the Al2O3-incorporated CISSe. Capacitance-voltage measurements reveal a reduced defect density by incorporation of Al2O3, which could be partly responsible for the higher VOC. Furthermore, using detailed surface analysis with various X-ray and electron spectroscopy methods, we derive chemical and electronic structure information from the surface. With ultraviolet photoelectron (UPS) and inverse photoemission spectroscopies (IPES), the electronic band gap of the CuIn(S,Se)2 thin-film surface is found to increase from 1.22 to 1.88 eV (+-0.12 eV) with Al2O3 incorporation. This is accompanied by a clear reduction of the conduction band spike at the CdS/CISSe interface due to Al2O3 addition, as derived by both UPS and IPES as well as temperature-dependent VOC measurements.« less

  2. Support of Adhesion Mechanisms in Al2O3 Aerosol Deposition Through Laser-Induced Particle Impact Testing

    Murray, Shannon Elizabeth ; Sarracino, Alex ; McPherson, Shane L. ; ... - Journal of Thermal Spray Technology
    Aerosol deposition (AD) is a kinetic spray process capable of depositing ceramic coatings at room temperature, but AD process development is generally a laborious exploration of a large process parameter space. Here, this paper presents a case study investigating whether laser-induced particle impact testing (LIPIT) could be applied to expedite development of an alumina (Al2O3) coating on nickel (Ni): Specifically, whether LIPIT measurements could predict critical velocities of adhesion on Ni and Al2O3, and the effect of ball milling the Al2O3 powder. Because LIPIT has a diffraction-limited lower bound on imageable particle size, the usefulness of Al2O3 powder agglomerates asmore » a proxy for single particles was additionally studied. Overall, LIPIT measurements and AD sprays agreed that ball milling dramatically improves adhesion. Additionally, LIPIT measurements of critical velocity of adhesion of Al2O3 powder agglomerates on Ni and Al2O3 substrates (150 meters per second [m/s] and 250 m/s, respectively) quantitatively agreed with predictions from a previously published model based on picoindentation and molecular dynamics simulations. Together, these findings support the established hypothesis that Al2O3 adheres via a dislocation-mediated mechanism in AD, that Al2O3 powder agglomerates adhere as individual constituent particles rather than collectively, and that, for this case study, LIPIT measurements were predictive of AD process parameters.« less

  3. Impacts of Focused Ion Beam Processing on the Fabrication of Nanoscale Functionalized Probes

    Wang, Xiang ; Taylor, Sandra D. ; Sassi, Michel J. ; ... - Inorganic Chemistry
    Herein, we examine the impact of Ga+ ion kinetic energy and the target material type on the extent of ion implantation and structural damage in atomic force microscopy probes made of Al2O3 and ZnO manufactured by focused ion beam (FIB) using scanning transmission electron microscopy and energy-dispersive X-ray mapping. Penetration of Ga into the Al2O3 lattice induced structural distortions and amorphization. For ZnO probes, Ga is uniformly dispersed across the surface, resulting in the formation of distinct clusters. Atom probe tomography further validates the Ga distributions in Al2O3 and ZnO nanoprobes. Complementary Monte Carlo simulations with the transport of ionsmore » in the matter program indicated that the introduction of Ga+ prompts the generation of cation and anion vacancies, an occurrence more pronounced in Al2O3 compared to ZnO. In conclusion, this study not only enriches the knowledge of ion-matter interactions, but also serves as a practical guide for the fabrication of nanoscale functionalized AFM probes.« less

  4. Nonpyrophoric alternative to trimethylaluminum for the atomic layer deposition of Al2O3

    Swarup, Jay V. ; Chuang, Heng-Ray ; Jensen, James T. ; ... - Journal of Vacuum Science and Technology A
    We have examined the atomic layer deposition (ALD) of Al2O3 using a nonpyrophoric precursor, which possesses only Al–N bonds and no Al–C bonds: Al(N(CH3)2)2(–N(C2H5)–C2H4–N(C2H5)2), which we refer to as bis-dimethylamino-diamino-aluminum (BDMADA-Al). We employed a quartz crystal microbalance (QCM) to monitor ALD in situ and in real time, and the deposited thin films have been characterized using x-ray photoelectron spectroscopy, spectroscopic ellipsometry, x-ray reflectivity, and atomic force microscopy. Films deposited with BDMADA-Al result in near-stoichiometric Al2O3 at temperatures ranging from T = 120 to 285 °C using H2O as the coreactant and at T = 285 °C using t-BuOH as themore » coreactant. The properties of the films (density, C incorporation, stoichiometry, growth rates) are comparable using either BDMADA-Al or trimethylaluminum (TMA) as the precursor under similar reaction conditions. The N content in the films deposited with BDMADA-Al as the precursor is <1% at both T = 120 and 285 °C. Additionally, both BDMADA-Al|t-BuOH and TMA|t-BuOH processes deposit near-stoichiometric Al2O3 at T = 285 °C, while neither process chemistry produces a constant growth rate per cycle at T = 120 °C. Close examination of single cycle QCM data from BDMADA-Al ALD indicates unique ligand exchange reaction mechanisms during each of the half-reactions. Experimentally, we have evidence supporting the mechanism in which upon the chemisorption of BDMADA-Al, the species on the surface retains the –N(CH3)2 ligands, while the diamine ligand is mostly lost on dissociative adsorption, except possibly at the higher temperature (285 °C). As a result, our work demonstrates that BDMADA-Al can be used as an effective alternative precursor to TMA for the ALD of Al2O3.« less

  5. Carboxyl-functionalized perovskite enables ALD growth of a compact and uniform ion migration barrier

    Choi, Deokjae ; Shin, Donghoon ; Li, Chongwen ; ... - Joule
    Mixed-halide wide-band-gap perovskites are critical components of highly efficient tandem cells, but their operating stability is limited by halide migration. Metal oxides deposited via atomic layer deposition (ALD) have been shown to block halide migration; however, previously pursued methods result in inhomogeneous nucleation and growth. We hypothesized that functionalizing the perovskite surface with ALD-active carboxyl groups could promote nucleation and enable higher-temperature metal oxide growth. We find that 5-ammonium valeric acid iodide (5-AVAI) facilitates the formation of a compact and uniform aluminum oxide (Al2O3) layer and allows growth at 100°C compared with the previous limit of 75°C. We demonstrate thatmore » halide migration into the C60 electron transport layer is reduced by a factor of 10 compared with the reference case. Finally, Al2O3-capped perovskite solar cells with a band gap of 1.78 eV retain 90% of their initial power conversion efficiency after 1,000 h of continuous operation under 1-sun illumination at 55°C.« less

  6. Revealing the corrosion mechanism of an Al0.1CoCrFeNi high entropy alloy in high temperature carbon dioxide environment

    Zhou, Shanliang ; Liang, Zihang ; Huang, Xi ; ... - Corrosion Science
    The corrosion behavior of an Al0.1CoCrFeNi HEA in high temperature CO2 at 850 °C for different exposure periods was investigated using different characterization methods. Further, weight gain increased with extended exposure periods, yet it remained lower than most conventional alloys. A double-layer oxide film consisting of Cr2O3 and Al2O3 formed after 100 and 500 h of exposure, while a single layer of Cr2O3 developed after 1000 h of exposure. CoCrFeNi particles with an FCC structure were embedded in the oxide films irrespective of the exposure periods. Moreover, a transition zone containing numerous striped-like Al2O3 oxides along the grain boundaries wasmore » developed underneath the oxide films.« less

  7. Enhanced Surface Passivation by Atomic Layer Deposited Al2O3 for Ultraviolet Sensitive Silicon Photomultipliers

    Tao, Yuguo ; Erickson, Anna - IEEE Transactions on Nuclear Science
    Here, we describe a superior passivation of p-type (p+) Si surface by Al2O3 thin film that is synthesized by plasma-assisted atomic layer deposition for ultraviolet sensitive silicon photomultipliers (SiPM), compared to conventional SiO2 and SiNx passivation schemes. The superiority of Al2O3 passivation is due to not only a sufficiently low interface defect density but also a high density of built-in negative charges. A 7 nm thin Al2O3 film can yield an emitter saturation current density of ~8 fA/cm2 on high sheet resistance p+ layer, compared to ~60 and ~1480 fA/cm2 for thermal SiO2 and SiNx passivation. This superior surface passivationmore » allows the photon-generated carriers to have higher probabilities to reach the high-field region to trigger an avalanche event. In addition, Al2O3 thin film provides very low values of effective surface recombination velocity on low resistivity n-type and p-type Si surfaces, which can lead to well-passivated surface features on guard ring and trench isolation regions of SiPM. These demonstrate the potential of Al2O3 thin film passivation to improve quantum efficiency and thus photo-detection efficiency of ultraviolet sensitive SiPM with p+/n-/n/n+ structure.« less

  8. Compatibility of FeCrAlMo in Flowing Pb-Li at 600°C to 700°C

    Pint, Bruce ; Jun, Jiheon ; Cakmak, Ercan ; ... - Fusion Science and Technology
    A series of monometallic thermal convection loops (TCLs) has been conducted to determine the maximum temperature where FeCrAl alloys have compatibility with eutectic lead lithium (Pb-Li) for a dual-coolant fusion blanket. Pre-oxidizing commercial alloy APMT (Fe-21Cr-5Al-3Mo) for 2 h at 1000°C to form a surface α-Al2O3 layer was very effective in reducing the mass loss of specimens in the hot and cold legs of the most recent TCL that was operated for 1000 h with a peak temperature of 700°C. However, unlike previous experiments, the postexposure room temperature ductility of many of the APMT specimens was degraded to <10% totalmore » elongation, and many of the specimens at the highest temperature (>680°C) were severely damaged or were not recovered. Furthermore, wide-angle X-ray scattering found that the pre-formed α-Al2O3 scale transformed to a mixture of trigonal and tetragonal LiAlO2. The overall results suggest that the maximum temperature for FeCrAl is limited to <700°C.« less

  9. In situ Al2O3 incorporation enhances the efficiency of CuIn(S,Se)2 solar cells prepared from molecular-ink solutions

    Septina, Wilman ; Muzzillo, Christopher P. ; Perkins, Craig L. ; ... - Journal of Materials Chemistry. A
    Here, we report an efficiency enhancement of solution-processed CuIn(S,Se)2 (CISSe) thin film solar cells via in situ incorporation of Al2O3. These films were produced using inks containing CuCl, InCl3, AlNO3 (Al/Al + In: 0.1) and thiourea dissolved in methanol. After spin coating of these solutions in air, samples were subjected to a selenization process. Auger electron spectroscopy depth-profiling analysis showed that Al is evenly distributed throughout the bulk of the film. Transmission electron microscopy revealed that AlNO3 precursor reacted with oxygen to form nanosized amorphous Al2O3 grains located within the bulk and grain boundaries of CISSe, as well as atmore » both the top and bottom interfaces. Power conversion efficiency (PCE) as high as 11.6% (JSC: 35.8 mA cm–2, VOC: 518 mV, FF: 62.2%, no anti-reflection coating) was achieved with Al–CISSe solar cell devices integrated with CdS (chemical bath deposition, thickness: 80 nm) and ZnO/ITO bilayers (sputtered, thickness: 300 nm). The average PCE (10.1%, $$\langle$$JSC$$\rangle$$: 34.5 mA cm–2, $$\langle$$VOC$$\rangle$$: 491 mV, $$\langle$$FF$$\rangle$$: 59.8%) was nearly 4% (absolute) higher than that measured on CISSe baseline cells fabricated from solutions without Al ($$\langle$$PCE$$\rangle$$ = 6.4%, $$\langle$$JSC$$\rangle$$: 32.8 mA cm–2, $$\langle$$VOC$$\rangle$$: 410 mV, $$\langle$$FF$$\rangle$$: 47.3%). This in situ Al2O3 incorporation is speculated to play a role in the enhancement of the VOC and FF of the devices through passivation of defects in CISSe reducing interface and bulk recombination, as evidenced by a reduced defect density and an increased activation energy of the dominant recombination mechanism from capacitance and temperature-dependent VOC measurements, respectively.« less

  10. Comparison of passivation properties of plasma-assisted ALD and APCVD deposited Al2O3 with SiNx capping

    Madani, Keeya ; Rohatgi, Ajeet ; Min, Kwan Hong ; ... - Solar Energy Materials and Solar Cells
    In this paper, we report on the direct comparison of Al2O3 films deposited by plasma-assisted atomic layer deposition (ALD) and atmospheric pressure chemical vapor deposition (APCVD) techniques on the passivation properties of both bare and boron diffused Si surfaces. It is found that ALD and APCVD deposited Al2O3 layers with SiNx capping have very similar chemical composition, hydrogen concentration at the Al2O3/Si interface, and interface defect density (Dit), but the ALD film has slightly higher negative fixed charge (Qf) after a high temperature (~750 °C) contact firing cycle typically used for solar cell fabrication. Both films showed excellent surface recombinationmore » velocities of <5 cm/s on planar and textured un-diffused Si wafers, but the ALD films gave 1 to 8 fA/cm2 lower emitter saturation current densities (J0e) on implanted boron emitters with sheet resistance in the range of 90–180 Ω/. This is attributed to the observed slightly higher negative charge-induced field-effect passivation in the ALD films. However, SiNx/Al2O3/p+/n/n+ passivated emitter rear totally diffused (PERT) cell structures fabricated with 110 and 150 Ω/ emitter in this study showed no appreciable difference in cell efficiency. Device analysis and simulations showed that even for >23% high-performance solar cells design, with very low bulk and rear contact recombination, the observed small difference in J0e has negligible effect on cell efficiency. Furthermore, APCVD Al2O3 passivation of B emitter can produce comparable efficiencies to their counterpart ALD Al2O3 passivated n-type Si solar cells.« less
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