Thin Film Combinatorial Capabilities for Advanced Water Splitting Technologies
LaboratoryNational Renewable Energy Laboratory (NREL)
Capability ExpertAndriy Zakutayev
Node Readiness Category2: High-Temperature Electrolysis (HTE)
2: Low-Temperature Electrolysis (LTE)
2: Photoelectrochemical (PEC)
2: Solar Thermochemical (STCH)
Previous capability name: "High-Throughput Experimental Thin Film Combinatorial Capabilities."
The thin film capabilities include combinatorial synthesis, spatially-resolved characterization, and semi-automated data analysis for thin film materials (see figure below).
1. Combinatorial depositions with intentional and well-controlled continuous gradients in process parameters (composition, temperature, film thickness, etc.):
- Wide range of thin film chemistries in separate chambers (metals, oxides, nitrides, sulfides, phosphides, Li-containing materials)
- Physical vapor deposition techniques (sputtering, pulsed laser deposition, molecular beam epitaxy)
- Different substrates and supports (glass, metals, crystals, ceramics, glassy carbon, etc).
2. Spatially-resolved characterization as a function of position on the thin film, and hence as a function of the graded thin film parameter:
- Chemical composition (XRF, RBS) and crystallographic structure (XRD, Raman)
- Microstructure (SEM, AFM) and surface properties (PES/XPS/UPS, KP)
- Electrochemical (SDC), electrical (impedence, conductivity, Seebeck), optical (uv-vis, FTIR, PL) properties.
3. Semi-automated data management and data analysis tools for deposition and characterization data:
- Custom-written processing functions and visualization routines implemented in Igor PRO
- Data harvesting into https://htem.nrel.gov/ database with API for machine learning
- Ongoing application-specific analytics development and integration with HydroGEN Data Hub.
Within the HydroGEN EMN consortium, high-throughput experimentations as described here can be closely coupled with predictive theory, focused materials synthesis, detailed characterization, and advanced data analytics to maximally accelerate materials discovery and development. The details of these other capabilities are described in other capability nodes.
Acronyms: XRF = X-ray fluorescence; RBS = Rutherford Backscattering; XRD = X-ray diffraction; SEM = scanning electron microscopy; AFM = atomic force microscopy; PES = photoelectron spectroscopy, with X-rays (XPS) and ultraviolet (UPS); KP = Kelvin probe measurements; PL=photoluminescence; FTIR=Fourier transform infrared spectroscopy; SDC = scanning droplet cell; API = application programming interface
Standard lateral sample size is 50x50 mm, but larger (up to 75–100 mm) and smaller (down to 3 mm) sample diameters are also possible. Effective thickness (size) range from ~1–10 nm to ~1–10 μm.
Any high-throughput experimentation combinatorial capability allows for faster screening of materials, which makes it unique compared to traditional serial experimentation methods. The unique aspects of these thin film combinatorial capabilities at NREL are (1) wide range of accessible combinatorial chemistries for O, N, S, P, Li, etc. (seven synthesis chambers) including mixed cation and mixed anion materials; (2) large number of complementary spatially-resolved characterization techniques (>10, see above); and (3) advanced state of digital data infrastructure (automated data harvesting, databases, analytics). In addition, NREL has >15 years of experience in integrating these three components of high-throughput experimentation workflow for advanced materials discovery and development, a unique level of experience in this field.
All the high-throughput experimentation capabilities are available for use by industrial and university partners as a part of the HydroGEN EMN for collaborative projects that would be mutually beneficial. Usually, there are a few work-for-others projects with industrial partners and several university collaborations at any given time. For example in FY18, this capability supported four different projects in three different HydroGEN categories (photoelectrochemical, solar thermochemical, and high-temperature electrolysis production of hydrogen). Please note that certain reactive (e.g., Ca) and toxic (e.g., Cd) metals may not be available in the existing synthesis chambers. The high-throughput experimental group at NREL welcomes visiting researchers, post-docs, and students, both for short informational visits (one or a few days) and for longer research-oriented stays (>6 months).
The high-throughput experimentation thin film capability can be used for different components of HydroGEN, including photoelectrochemical (PEC) water splitting (light absorbers [1a], evolution catalysts, protection layers [1b]), advanced electrolysis (AE) materials (low-temperature catalysts, high-temperature ion conductors and catalysts), and solar thermochemical hydrogen (STCH) production (redox-active materials). In each of these categories, this combinatorial thin film capability can be applied not only to materials discovery [1a,1b] (e.g., new PEC light absorbers, non-PGM AE catalysts, complex STCH redox materials) but also to materials integration [1c] (e.g., Schottky barriers between absorber and catalyst, protection layers, interface defects, coating thickness, etc.).
Schematic illustration of the high-throughput experimental capabilities at NREL, including combination synthesis, spatially-resolved characterization, and semi-automated analysis. Please see the description section for more details.
Find more information about high throughput experimentation approach at NREL, including instrumental capabilities and publication examples.
1. Examples of use of the combinatorial thin film capability at NREL from the past:
1a. Transparent conductive coatings:
- p-type - Chem. Mater., 29, 8239, (2017); J. Mat. Chem. C, 6, 6297 (2018); MRS Communications 1, 23 (2011)
- n-type - ACS Appl Mat Int 8, 14004 (2016); ACS Combinatorial Science 18, 583, (2016); Sol En Mat 159, 219, (2017)
1b. Novel light-absorbers suitable for PEC:
- nitrides—J. Mater. Chem. C, 3, 1389 (2015); Adv. Electronic Mater.,1600544(2017); J. Am. Chem. Soc., 140, 4293 (2018)
- sulfides—Chem. Mater. 26, 4951 (2014); Solar Energy Materials and Solar Cells 132, 499 (2015); APL Materials, 6 084501 (2018)
- oxides—Phys. Rev. X 5, 021016 (2015); Chemistry of Materials 28, 7765,(2016); Appl. Phys. Lett. 106, 123903 (2015)
1c. Other relevant topics:
- Materials integration: Appl. Phys. Exp. 8, 082301 (2015); Adv. Energy Mat., 7, 1601935, (2017); Adv. Mater. Interfaces, 3, 1600755 (2016)
- Materials informatics: Scientific data, 5, 180053 (2018); Materials Discovery, 10, 43 (2017); Appl. Phys. Rev. 4, 011105 (2017)