In the Ratcliff group, we are interested in low cost, printable semiconducting materials and interfaces for energy harvesting and storage and bioelectronics, all with reduced manufacturing cost and lessened environmental impact.
(Photo)Electrochemical Cells for Energy Conversion and Storage
Polymer/liquid interfaces are critical for energy conversion in solar fuels and molecular catalysis, batteries (including redox flow), supercapacitors, fuel cell, thermogalvanic, electrochromic, and novel dye cell applications.
Polymers are highly advantageous, as the electronic properties can be tuned to match redox potentials of small molecule targets such as CO2 or H2O or other redox-active molecules, while also controlling optical properties for photon absorption. If we can understand transport phenomena and charge transfer of polymer/electrolyte interfaces, we can drive the search for new materials with improved functionality. In the Ratcliff group, we are developing interfacial design strategies to control matter on the atomic scale and how to characterize the functionality of these interfaces at relevant length scales (nano to micron). We use a number of spectroscopy and microscopy techniques that are coupled with electrochemistry. Interested students and postdocs should have experience with electrochemistry, spectroscopy, or conductive polymers. For more information about these efforts, visit us at specs.arizona.edu.
This work is currently funded by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0020208 and through the SPECS Energy Frontier Research Center under Award Number DE-SC0023411.
"Rationalizing energy level alignment by characterizing Lewis acid/base and ionic interactions at printable semiconductor/ionic liquid interfaces" Materials Horizons, 2022, 9, 471-481. DOI: 10.1039/D1MH01306H.
"Ion diffusion coefficients in poly(3-alkylthiophenes) for energy conversion and biosensing: role of side-chain length and microstructure" Journal of Materials Chemistry C, 2020, 8, 13319-13327. https://doi.org/10.1039/D0TC03690K
Interfaces and Stability in Perovskite Solar Cells
Solar cells convert sunlight into electricity. Since the 1950’s, silicon has been the primary semiconductor material used in solar cells. The issue is that the silicon crystals require an expensive, multi-step manufacturing process that utilizes a lot of energy. Alternatively, new thin film approaches can be mass produced using roll-to-roll fabrication procedures from simply formulated inks.
"Surface-Activated Corrosion in Tin-Lead Halide Perovskite Solar Cells" ACS Energy Letters, 2020, 5, 11, 3344-3351. https://doi.org/10.1021/acsenergylett.0c01445
"Overcoming Redox Reactions at Perovskite-Nickel Oxide Interfaces to Boost Voltages in Perovskite Solar Cells" Joule 2020, 4, 8, 1759-1775. https://doi.org/10.1016/j.joule.2020.06.004
Organic Photovoltaic Materials and Devices
Indoor photovoltaics (iPV) can harvest ambient light to power the internet of things. Building integrated photovoltaics (BIPV) can transmit certain portions of the color spectrum as solar windows, greenhouses, and mobile architectures. We are interested in the structure-property relationships of materials, device photophysics, and long-term stability.
This work is currently funded by the National Science Foundation under the Solid State Materials Chemistry program in DMR -2003631
"A New Perylene Diimide Ink for Interlayer Formation in Air-Processed Conventional Organic Photovoltaic Devices" ACS Applied Materials and Interfaces, 2022, https://pubs.acs.org/doi/full/10.1021/acsami.2c12281
"Zinc Oxide-Perylene Diimide Hybrid Electron Transport Layers for Air-Processed Inverted Organic Photovoltaic Devices" ACS Applied Materials and Interfaces, 2021, 13, 41, 49096–49103. https://pubs.acs.org/doi/full/10.1021/acsami.1c15251.
"A Multi-modal Approach to Understanding Degradation of Organic Photovoltaic Materials" ACS Applied Materials and Interfaces, 2021, 13, 37, 44641–44655. https://pubs.acs.org/doi/full/10.1021/acsami.1c12321.
"Slot-Die-Coated Ternary Organic Photovoltaics for Indoor Light Recycling" ACS Applied Materials and Interfaces, 2020, 12, 39, 43684–43693 https://pubs.acs.org/doi/10.1021/acsami.0c11809
Organic Bioelectronics for Wearable Sweat Sensors
Interfacing electronic materials with biological systems improves understanding of bimolecular interactions and promotes application of solid-state devices in biology and medicine. One key area of interest is molecular sensing, focusing on detection of biomarkers in human sweat for local or remote monitoring of human operator function. Conductive polymers are especially promising bioelectronic materials, with high flexibility to match tissue modulus, low toxicity, and electronic properties that are highly influenced by both electrical charges and ions.
Organic electrochemical transistors (OECTs) and electrolyte-gated organic transistors leverage the hybrid electrical-ionic conduction mechanism of organic semiconductor active elements. This unique conduction property yields higher transconductance and lower operating voltages relative to inorganic transistors, with enhanced sensitivity in high ionic strength environments. We are interested in fundamental structure-property relationships and transport properties of these materials, interfaces and devices and on development of wearable sweat sensing devices using new architectures.