20 Nov
2017
20 Nov
'17
3:06 p.m.
Please post and forward to your groups:
Center the Excitonics/Perovskite Seminar Series presents:
Historic Overview and Design Principles for Optoelectronic Perovskite Materials*
November 22, 2017 at 4:30pm/rm: 35-520
Michael Saliba
École polytechnique fédérale de Lausanne (EPFL) Station 6, 1015 Lausanne
[http://www.rle.mit.edu/excitonics/wp-content/uploads/2017/11/saliba_1.jpg]
This presentation gives a general overview of the rapidly evolving field of perovskite
solar cells (PSCs). Reasons why perovskite solar cells have triggered such enthusiastic
feedback from research groups all over the world are discussed. The current challenges
and approaches of the field are exemplified using a high-performance model systems for
PSCs (a triple cesium (Cs), methylammonium (MA), formamidinium (FA) cation perovskite).
The triple-cation composition achieves power conversion efficiencies (PCEs) close to 21%
and stabilized power outputs at 18% under operational conditions over 250 hours (maximum
power point tracking under full illumination held at room temperature). Adding Cs to MA/FA
mixtures, which are currently among the highest performing compositions, suppresses yellow
phase impurities and induces uniform perovskite grains extending from electron to hole
collecting layer consistent with seed-assisted crystal growth. The triple cation
perovskites are more robust to subtle variations during the fabrication process enabling a
breakthrough in terms of reproducibility where PCEs > 20% were reached on a regular
basis (in contrast to the MA/FA only devices).
The principle of mixing cations can be taken further. Through multication engineering, the
seemingly too small rubidium (Rb) can be integrated (despite never showing a black phase
as a single-cation perovskite). The composition containing Rb, Cs, MA and FA results in a
stabilized efficiency of 21.6% as well as an electroluminescence of 3.8%. The open-circuit
voltage of 1.24 V at a band gap of 1.63 eV leads to one of the smallest
losses-in-potential (of 0.39 V) ever measured for any PV material. Polymer-coated cells
maintained 95% of their initial performance at 85°C for 500 hours under full solar
illumination and maximum power point tracking. This is a crucial step towards
industrialisation of PSCs.
Dr. Michael Saliba is a Marie Curie Fellow at EPFL working with the Grätzel and Hagfeldt
groups. He completed his Ph.D with Prof. Henry Snaith at Oxford University in 2014 working
on crystallization behavior and plasmonic nanostructures in hybrid organic-inorganic
perovskite thin films. He holds a BSc in mathematics and physics from Stuttgart
University. His research focuses on a deeper understanding and improvement of
optoelectronic properties of emerging photovoltaic technologies with an emphasis on
perovskites for a sustainable energy future. In 2016, he was awarded the "Young
Scientist Award" of the German University Association. In 2017, the MIT Technology
Review named him as one of the World's "35 Innovators under 35".
Light refreshments will be served
*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
