Theme: Photons in Applied Materials
Example Project: Molecular interfaces controlling photons in plastic electronics
Faculty Mentor: Brian Collins
Printable devices based on molecular materials have the potential to revolutionize how we use technology, renewably harvest energy, and even stay healthy. These devices are already being used in iPhone screens and in flexible/foldable LED displays. Future disruptive technologies are roll-to-roll printed solar panels and batteries,  wearable biosensors,  or even drug delivery platforms.  A major area of exploration is how molecules organize after printing to control the electronic and photonic processes that occur within these devices. Our lab controls how molecules are deposited to form devices, probes their nanostructure with advanced X-ray techniques, and correlates that structure to excited state dyanmics and device performance. One NSF project seeks to understand how charge separation and recombination (critical for solar cells and LEDs) is impacted at a molecular interface by molecular packing and orientation at that junction. Our work has demonstrated that photocurrent generation is controlled by both the interfacial molecular orientation  and diffuse vs sharp interfaces.  We aim to reveal the mechanisms at play such that future printable devices can be engineered for high performance tailored to their application.
The REU scholar, faculty mentor, and graduate student will compose a team to investigate how light interacts with molecular interfaces in “organic” solar cells (OSCs) to generate electrical power. OSCs will be constructed by the scholar from molecules deposited via inks (solution printing) or physical vapor deposition. The REU scholar will conduct pulsed laser measurements to characterize excited state dynamics under real operating conditions. The scholar will vary the nature of this interface through device processing and will travel with our group to the Advanced Light Source at Berkeley National Laboratory to measure the structure of device interfaces through X-ray microscopy, spectroscopy, and scattering experiments – thus connecting the interfacial structure to the interfacial photon dynamics.
Prof. Brian Collins has only been a faculty for 5 years but has already advised or is advising 10 undergraduate students in their thesis projects and 5 high school summer projects through Upward Bound. Underrepresented minorities include two undergraduates (Native American and African American), and three high school students (two women and one Hispanic). Two undergraduates defended their thesis for Honors with Distinction and additionally won the Crimson Award for the best poster at the annual Showcase for Undergraduate Research and Creative Activities. One undergraduate was named an Auvil Scholars Fellow for his research and was a coauthor on a peer-reviewed research paper in Journal of Materials Chemistry A (IF=11).  All high school students are now attending college and of the six undergraduates who already graduated one is in industry, one is in the Navy, and the rest are in graduate school for their PhD in engineering or physics.
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 Tumbleston…, Nature Photonics (2014) DOI: 10.1038/nphoton.2014.55
 Ferron…, Journal of Materials Chemistry A (2019) DOI: 10.1039/c8ta12336e