CHEE Seminar: Michel De Keersmaecker
Monday, September 19, 2022
3:00 p.m.
Michel De Keersmaecker
Postdoctoral Research Scientist
Department of Chemical and Environmental Engineering
The University of Arizona
"Stability in Triple Cation Perovskites: From Counting Defects to Operando Degradation"
Harvill Bldg., Room 305
Social Hour immediately following seminar in Harshbarger 118B, at 4:00 PM
ABSTRACT
Strategies to measure, understand and improve stability in perovskites often trace back to the presence of electronic defects, but rarely their chemical makeup and reactivity is considered. Hence, directly probing these reactive defect densities under operando conditions (i.e. away from equilibrium condictions) and correlate their chemical, electronic and physical nature to comprehend degradation mechanisms will be critical for the development of a much-needed, powerful, quality and durability evaluation tool.
Here, De Keersmaecker will demonstrate an electrochemical methodology based on a half-cell device stack using a "peel and stick" electrolyte top contact, that is easily combined with spectroscopic characterization techniques to study stability in triple cation perovskites. Systematic modulation of the potential and the introduction of specific redox probes to support electron and hole injection allows us to draw the most complete electronic band structure of a perovskite and by extension any semiconductor. By reducing charging currents and improving energy resolution, unprecedented detection limits are reached when probing the density of states and surface defects with the additional benefit of identifying their (electro)chemical reactivity. Combined with X-ray scattering techniques, we illustrate that this controlled polarization allows the collection of bias-dependent structural data to gain insight into real-time operation and damage evolution processes.
In short, this electrochemical probe is shown to overcome challenges in quantifying defects in printable electronic materials and to promote operando analysis of thin film perovskites, organic semiconductors, quantum dots, conventional semiconductor materials, material blends and device stacks, where the removable solid electrolyte functions as the “top contact”. This type of advanced electrochemical characterization platform will prove to be crucial for the quality control of low cost (opto)electronic materials and device stacks as well as the improvement of their stability and durability in order to realize industry-scalable technologies in the field of photovoltaics, charge storage systems, photoelectrochemical cells, etc.
BIOSKETCH
Michel De Keersmaecker is a research scientist with the Department of Chemical and Environmental Engineering at the University of Arizona. He is a analytical (electro)chemist and materials scientist with extensive research experience in the field of energy storage, optoelectronics and corrosion science. His research interests have involved lead halide perovskites and electroactive conjugated polymers with work focused on the development of multimodal and in situ approaches to study their optoelectronic and redox properties. Being a Belgian native, De Keersmaecker obtained his M.S. (2009) and Ph.D. (2015) degrees in chemistry from Ghent University. In 2016, he moved to the Georgia Institute of Technology to work on conjugated polymers as active materials in supercapacitors, electrochromic devices and antennas in the group of John Reynolds. His current research is directed towards developing an electrochemical probe for defect quantification in semiconductor materials critical to the design of next-generation oproelectronic platforms. He has published over 22 peer-reviewed scientific papers and has 1 patent pending. He has reviewed for Electrochimica Acta, Chemistry of Materials and Materials Advances.