Research Topics

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. 

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, including color retention.  

 

 

(Photo)Electrochemical Cells for Energy Conversion and Storage

Polymer/liquid interfaces are critical for energy conversion in solar fuels and molecular catalysis, redox flow batteries, 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).  

 

This work is currently funded by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0020208. 

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.

This work was in part previously funded by the National Science Foundation under DMR #1608289 and by the Nano-Bio Materials Consortium #NB17-16 and is currently funded by the Nano-Bio Materials Consortium #NB18-19-18. 

 

Interfaces 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.

Metal halide perovskite materials are low-cost, solution-processable materials that have demonstrated single-junction power conversion efficiencies above 25%.  Our group is interested in critical interface challenges that continue to limit industrial scaling.   
 
This work is currently funded by the Office of Naval Research under award number N00014-20-1-2440.