Thin-Film Photovoltaics
 
 

Allen Hall

I have a long history with the department of Materials Science and Engineering, having entered the department after High-school, and continuing on through Graduate School, first as a Masters candidate, shortly thereafter as a PhD Candidate.  My original focus in undergraduate was on polymers with a focus in mechanics of composites.  As a freshman I walked into the department head's office, sat down, and said: "So, what the heck does a Materials Scientist do anyway?..."  That started a look into the research which was being accomplished in this award-winning department.  The professors here have never ceased to amaze me with their intellectual interest in exploring all aspects of materials and in novel new ways of exploiting our knowledge to solve problems.

Before I worked in materials research, I worked with Prof. James Adams in the creation of hands-on projects for High-School students interested in Engineering. (JETS)  Under his guidance, I developed a number of experiments, ranging from the ever-popular making of "goop" to coloring and molding glass with a focus on observation of internal stresses and annealing.  The experience was amazingly rewarding, and to this day I remember playing around with shape-memory alloys and the wonderful and ever-present help of Joe Grindley (glass-blower, machinist, and problem solver).  This early work showed me that laboratory experiment creation and exploratory teaching was excellent fun.  [Some of our experiments were also made into NSTA High-School teaching experiments.]

My early undergraduate research work was focused on Chemically Tailored Activated Carbon Fabrics for Environmental Contaminants.  Very interesting work, with the primary discoverer of Activated Carbon Fabrics (ACF's).  Under the direction of Chris Mangun, then a graduate student, I collected data on Fixed Bed Adsorption experiments, chemically tailored ACF's for adsorption, learned how to deal with an amazing number of data points in a unique way (gawk is a scientists friend), and yes, washed my fair share of glassware.  :)  Shortly after my undergraduate work, I was involved in work with Dan Frich on data-analysis of his final experiments for his PhD.  Specifically, genetic algorithm modeling of neutron-diffraction experiments performed on samples of material solid-state bonded via interchain transesterification reactions which were performed at the APS at Argonne National Labs.

This began my work in polymer research.  For a number of following years I was working on the synthesis of a number of new resins.  Of course some work was done on the synthesis and processing of all-aromatic polyester thermosetting resins.  We also produced a variant of this system (with Frank Shi) which had a tailored pendant uv-sensitive end-group for use as a photo-resist.  I produced a low-cost resin based on alkyd/glyptal resins for use in medium-temperature applications as well as exploring interchain transesterification reactions for solid-state bonding of nylons.  Perhaps the most exciting time was had when I came across an interfacial polymerization method utilizing ultrasonic emulsions for producing thermoset nanoparticles which could then be used as a solid-consolidation powder.  TEM confirmed the synthesis route was successful at creating nanoparticles.  [I had suspicions when I saw the powders I produced hang in the air like a cloud once sprayed.]

Shortly after this discovery, I moved my focus in work to semiconductors.  More specifically to photovoltaics and CuIn(Ga)Se2 thin films.  In my first project, I designed and installed a capacitively coupled RF plasma coil which was used for ion-assisted PVD.  During this project I worked closely with an expert machinist (Spencer Schultz), learning about the art of machining.  The day the first purple plasma glow came out of the coil, was truly a fantastic one!  We have been able to produce some really intriguing new morphologies with the iPVD approach, currently this work is unpublished.

Shortly after the iPVD project, during our group-meetings, we were discussing the strange nature of grain-boundaries in CuInSe2.  After a bit, I piped up and said: "I wish we could just study a single-grain boundary.  That would make things a ton easier..."  Prof. Rockett looked over and said: "But- We can!"  :)  And so a new research project was started.  Shortly after I obtained poorly grown GaAs wafers which were CMP polished (with no promises) by Wafer Tech Co. UK.  Luckily these guys understood what we needed.  After some failures, we finally grew the first epitaxial bicrystal CuInSe2 film in our field.  The high-angle grain-boundary grew beautifully into the film, as well as all twins.  Recent work has been focused on the influence of grain-boundaries on the growth of the CuInSe2 films.  Interesting morphologies have been found, as well as some hints that grain-boundaries may be influencing growth in ways that may have ramifications to all device quality films.  [I'll have to leave this here until we publish.]

After this long time of research, I'm excited by the prospects of future work.  There are so many new and exciting developments in the field of Materials Science and Engineering.  Just the prospect of the interaction of my two areas of graduate-research (polymers and semiconductors) has me intrigued.  In the past I've been interested in bio-materials, specifically the tailoring of polymer scaffolds (which I didn't have a chance to pursue my ideas in, unfortunately), and interface tailoring for composites.  I think that I may try my hand at the business world, see what that is like, and perhaps, in the future, come back to teach more.  If you're one of my past students, please don't ever hesitate to get in touch!  I'd love to hear from you.

Publications

A. J. Hall, D. Hebert, C. Lei, A. Rockett, and S. Siebentritt. Epitaxial growth of very large grain bicrystalline Cu(In,Ga)Se2 thin films by a hybrid sputtering method. Journal of Applied Physics, 103(8):083540, 2008.

AVS October 2007 Poster

 
News

Professor Angus A. Rockett • Phone: (217) 333-0417 • Fax: (217) 333-2736 • Email: arockett@uiuc.edu