ChE Seminar Series: Reviving “Fool’s Gold” as a Photovoltaic Material


9:35 am-10:30 am
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Eray S. Aydil, Ph.D.
Alstadt Lord Mark Professor
Editor-in-Chief Journal of Vacuum Science & Technology
Tandon School of Engineering Chemical and Biomolecular Engineering Department
New York University

Pyrite FeS2, (fool’s gold) has long been considered an ideal semiconductor for low-cost, sustainable solar cells because it is composed of earth-abundant, non-toxic, inexpensive elements and it absorbs light so strongly that a 100 nm thick film can absorb >90 % of incoming sunlight. Pyrite was pursued vigorously in the 1980’s for thin film solar cells but all attempts failed, with disappointing efficiencies, less than 3 %. With the rise of other high efficiency thin film solar cells, such as CdTe and CuInGaSe2(CIGS), enthusiasm for pyrite vanished. Fool’s gold was dead as a solar cell material. Interest in FeS2reemerged around 2009 motivated in part by the sustainability, cost, and toxicity concerns with CdTe and CIGS. This time, however, a few groups, including ours, are pursuing the fundamental origins of the disappointing performance of FeS2rather than attempting to produce efficient cells viathe trial-and-error approach that previously failed. For three decades, electronic transport data from thin FeS2films were interpreted as p-type, while single crystals have been unambiguously established as n-type. This unexpected difference came to be known as the “Doping Puzzle”. Recently, we resolved this puzzle and showed that FeS2films are not p-type but in fact n-type. In thin films with low mobility hopping conduction artificially inverts Hall coefficient, incorrectly indicating p-type conduction. For three decades, FeS2based solar cells might in fact have been designed based on a mistaken presumption. In this talk I will summarize our recent efforts in collaboration with Prof. Chris Leighton at the University of Minnesota in reviving FeS2 as a photovoltaic material.1-3

1.Zhang et al., Phys. Rev. Materials1, 015402 (2017).
Voigt et al., ACS Applied Materials & Interfaces11, 15552 (2019).
Voigt et al., ACS Materials Letters 2, 861-868(2020).
Biography: Eray S. Aydil is the Alstadt Lord Mark Professor of Chemical and Biomolecular Engineering at New York University (NYU) Tandon School of Engineering. Previously he was the Christenson Chair in Renewable Energy and Executive Officer of the Department of Chemical Engineering and Materials Science (CEMS) at the University of Minnesota (UMN). He is a Fellow of the American Vacuum Society (AVS) and Editor-in-Chief of the Journal of Vacuum Science and Technology. He received his B.S. degrees in chemical engineering and in materials science, both from U. C. Berkeley in 1986, and his Ph.D. degree in chemical engineering in 1991 from the University of Houston. He was a postdoc at Bell Labs until 1993 when he joined the faculty of the chemical engineering department at U.C. Santa Barbara (UCSB) as an assistant professor. By the time he left UCSB in 2005 for UMN, he was a professor and vice chairperson. In 2005, Dr. Aydil joined the Department of Chemical Engineering and Materials Science (CEMS) at UMN where he remained until 2018; between 2009 and 2014 he served as the Executive Officer of CEMS. In 2018 he moved to NYU. He has published over 200 articles and holds seven patents. His research interests range from optoelectronic materials and solar cells to plasma processing. In recognition of his research, he has received the Peter Mark Award and the Plasma Prize from the AVS, the Norman Hackerman Young Author Award of the Electrochemical Society, the National Young Investigator Award of the NSF, and the Camille-Dreyfus Teacher-Scholar Award. He is a Fellow of the UMN Institute on the Environment. He has received numerous teaching awards including Professor of the year award several times at UCSB and most recently the Horace T. Morse-UMN Alumni Association Award for Outstanding Contributions to Graduate and Professional Education in 2017.


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