Flexible quantum materials for spectrally selective solar energy harvesting


Colloidal quantum dots (CQDs) are an attractive third-generation material for photovoltaics due to their solution-processability, lightweight and flexible nature, and bandgap tunability, allowing them to be used as infrared materials for multi-junction solar cells. I will discuss several methods for building new lead sulfide-based CQD materials and thin films for improving efficiencies and expanding spectral applications in both single-junction and multi-junction solar cells. First, we use sulfur doping and 2D transition metal dichalcogenides to improve solar cell efficiency via enhancement of the performance-limiting hole transport layers. Next, we demonstrate a multi-modal micrometer-resolution 2D characterization method with millimeter-scale field of view for assessing CQD solar cell film quality and uniformity. We use this high-resolution morphology mapping to quantify the distribution and strength of the local optoelectronic property variations in CQD solar cells due to film defects, physical damage, and contaminants across nearly the entire test device area, and the extent to which these variations account for overall performance losses. We then use the massive data sets produced by this method to train machine learning models that take as input simple illuminated current-voltage measurements and output complex underlying materials parameters, greatly simplifying the characterization process for optoelectronic devices. Finally, we use artificial photonic band engineering as a method for achieving spectral selectivity in absorbing PbS CQD thin films for applications in multi-junction photovoltaics. We show that a structured periodic CQD thin film is able to maintain a photonic band structure, including the existence of a reduced photonic density of states, in the presence of weak material absorption, enabling modification of the absorption, transmission, and reflection spectra. We use a machine learning-based inverse design process to generate CQD thin film photonic structures with targeted absorption, transmission, and reflection spectra for multi-junction photovoltaics and narrow bandwidth photodetectors.


Susanna M. Thon is an Associate Professor of Electrical and Computer Engineering and the Marshal Salant Faculty Scholar at Johns Hopkins University. Her research is in nanomaterials engineering for optoelectronic devices, with a focus on solar energy conversion and sensing. Thon’s work has received funding from the National Science Foundation, Maryland Energy Innovation Institute, TEDCO Maryland Innovation Initiative, American Chemical Society, and the Department of Defense. She is the recipient of Johns Hopkins’ Catalyst and Discovery awards and the National Science Foundation CAREER award. More than 50 of her research papers have been published in peer-reviewed journals, and she is a past chair of the Optical Society of America’s Optics for Energy Technical Group. Thon received her bachelor’s degree from MIT in 2005 and her master’s and Ph.D. (all in Physics) from the University of California Santa Barbara in 2008 and 2010, respectively. Prior to joining Johns Hopkins in 2013, she worked as a postdoctoral fellow at the University of Toronto.


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