"Nanoscale Control of Light and Energy"

Abstract:  Modern nano-materials offer an almost infinite application space, with huge advances made recently in fields as varied as solar cells and LEDs to 3D printing and optogenetics. In particular, combining different material systems has allowed us to uncover novel and exciting physics and applications. In this talk, I will discuss nano-material breakthroughs across several fields, with a particular focus on high-energy perovskite LEDs and applications of photon upconversion and downconversion.

Perovskite LEDs are an exploding field, with high performance red and green devices demonstrated by many groups. Blue LEDs, however, have lagging significantly behind. Here, we identify two crucial issues holding these materials back: the low internal photoluminescence yield and the LED device structure itself. By rectifying these issues, we were able to build LEDs that were 60x brighter than control, competitive with their red and green cousins, and demonstrate both white and UV LEDs.

Photon upconversion and downconversion allows us to convert between colors of light while conserving energy. We demonstrate that these processes allow for huge advancements in photovoltaic technology by circumventing the single junction thermodynamic limit, achieving quantum efficiencies greater than 100% utilizing downconversion and infrared-to-visible harvesting using upconversion.  Further, using nanoscale encapsulation to add upconversion to a 3D printing resin, we can circumvent the layer-by-layer nature of traditional 3D printing and print in a truly volumetric fashion without supports or resin flow constraints.

Bio: Dan Congreve received his B.S. and M.S. from Iowa State in 2011, working with Vik Dalal studying defect densities of nano-crystalline and amorphous silicon. He received his PhD from MIT in Electrical Engineering in 2015, studying under Marc Baldo. His thesis work focused on photonic energy conversion using singlet fission and triplet fusion as a downconverting and upconverting process, respectively. He spent a year as a postdoc with Will Tisdale in Chemical Engineering at MIT studying perovskite nanoplatelets. He joined the Rowland Institute in August 2016 and started at Stanford University as an Assistant Professor of Electrical Engineering in 2020. Dan is a 2019 Moore Inventor Fellow, 2020 Terman Faculty Fellow, 2022 Sloan Research Fellow, and co-founder of Quadratic3D, a startup looking to commercialize 3D printing technologies. His current research interests focus on applying nanomaterials and nanotechnology to challenging problems.