New subject: [Aspuru-Guzik Group List] Excitonics/Perovskite Seminar, TODAY, Nov 17 at 12 noon: 34-401B

17 Nov 2017

Center for Excitonics/Perovskite Seminar Series presents:

How to assess operational stability of perovskite solar cells with reversible
degradation?*
November 17, 2017 at 12 noon/ rm: 34-401B
Eugene Katz
Ben-Gurion University of the Negev, Israel/ Department for Solar Energy and Environmental
Physics
[http://www.rle.mit.edu/excitonics/wp-content/uploads/2016/12/katz..jpg]
Development of hybrid organic-inorganic halide perovskite solar cells (PSCs) combining
high performance and operational stability is a key issue for implementation of this
technology. Both reversible improvement and reversible degradation of PSC efficiency were
previously reported under illumination-darkness cycling. Quantifying the performance and
stability of cells exhibiting significant diurnal performance variation is challenging and
requires specific protocols. In this talk I will discuss outdoor stability measurements of
two types of devices showing either reversible photo-degradation or pronounced reversible
efficiency improvement under sunlight-soaking. Analysis of the results suggests that the
figures of merit for photovoltaic performance and stability of such devices should be
reconsidered. Instead of the classical approach of reporting the initial (or stabilized)
efficiency value and estimation of T80, we propose to use the value of energy output
generated during the first day of the exposure (or first illumination period in the
light/darkness cycling indoor) and the time needed for reaching its 20% drop,
respectively. The latter accounts for both the long-term irreversible degradation and the
reversible diurnal efficiency variation and does not depend on the type of processes
prevailing in a given perovskite cell.
Possible underlying mechanisms for reversible, irreversible and apparently irreversable
performance losses will be discussed on the basis of I-V curves evolution, transient
electrical measurements and photoluminescence studies.
Eugene A. Katz received his MSc degree in Semiconductor Materials Science in 1982 and Ph.
D. in solid state physics in 1990 from the Moscow Institute of Steel and Alloys. He has
research experience in field of photovoltaic materials and devices for more than 30 years.
The topic of his Ph. D. thesis was "Atomic structure and electronic properties of
grain boundaries in polycrystalline silicon solar cells". In 1995, he joined the
Ben-Gurion University of the Negev and has been working in the Department for Solar Energy
and Environmental Physics ever since (now as a full professor). His research interests
include areas of applied solar energy, photovoltaics based on non-traditional
semiconductors (fullerenes, nanotubes, conjugated polymers, perovskites), photovoltaic
characterization of AIIIBV concentrator solar cells at ultra-high concentration of natural
sunlight (up to 10,000 suns) and synthesis of nanomaterials by concentrated sunlight. He
has published more than 100 peer-reviewed papers on these topics. In addition, has
published a book and articles for broader audiences on the history of science and
fullerene-like structures in nanomaterials, living organisms and architecture.
*This talk is part of the Perovskites Seminar Series organized by Juan-Pablo Correa-Baena
from MIT's PV Lab and sponsored by the Center for Excitonics. For more info contact
Juan-Pablo: jpcorrea@mit.edu<mailto:jpcorrea@mit.edu>
The Center For Excitonics Is An Energy Frontier Research Center Funded By The U.S.
Department Of Energy,
Office Of Science And Office Of Basic Energy Sciences