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ABSTRACT: A new type of organic-inorganic hybrid perovskite has appeared to be a wonder material for its outstanding tolerance to defects, excellent absorption across visible spectrum, long range carrier diffusion, etc. In the past decade, it has been emerged as a superstar material for photovoltaic, optoelectronic and photoelectronic applications. In only a few years, its solar cell efficiency has been increased from original 3.8% to current 25.5%. Furthermore, the solar cell fabrication processes based on the planar architecture have been particularly enthusiastic thanks to their low temperature fabrication and compatibility with a range of substrates. Comparing solution deposition with vacuum deposition, the vacuum processes for thermal co-deposition and sequential deposition of PbCl2 and CH3NH3I materials are recognized as efficient means to prepare perovskite film with good uniformity and high surface coverage. A vacuum deposition process has been developed to fabricate large-area high-efficiency perovskite solar cells with high stability using alternating precursor layer vacuum deposition. The new deposition process allows us to relax the strict deposition monitoring and control measures, while realizing superior uniformity in film morphology, surface coverage and smoothness, together with crystalline phase purity.
For the high efficiency perovskite solar cells, the power conversion efficiencies for the planar device is as high as 24.9%. More importantly, we have developed a superior low temperature modified SnO2 material for ETL and transferred the cell fabrication process onto lightweight flexible polymeric substrate. The highest cell efficiency achieved is 24.8% on rigid substrate and over 21% on the flexible one, it is also the highest efficiency among the flexible perovskite cells reported. Furthermore, upon bandgap engineering, we developed a method to fabricate perovskite solar cell for low light applications. It is found that this type of cells are particular efficient in room light condition with power conversion efficiency as high as over 40%. Meanwhile, the devices show very good stability over long term exposure in ambient with very low degradation. After a representative cell was exposed in ambient lab condition for a year, its final cell efficiency is as high as over 95% of its initial efficiency with its degradation accounts for only smaller than 5%. Further analysis on the stability of the perovskite solar cells will be discussed. We have also developed a series of single-crystalline perovskites with superior stability and optoelectronic performance.
BIOGRAPHY: Prof. Shengzhong Liu
received his MSc in Chemistry from Lanzhou University in 1986 and his PhD from
Northwestern University, USA in 1992. Upon completing his postdoctoral research
at Argonne National Laboratory in 1994, he joined high-tech industrial
research, most notably on solar cells with Solarex/BP Solar and United Solar
Ovonic. Professor Liu’s research focus includes nanomaterials, thin film
materials, photovoltaic materials and solar cells. His major outcome in basic
research are published in scientific journals, including Science, Nature, Joule, Matter, Science
Advances, Nature Communications, Advanced Materials, Energy & Environ.
Sci., etc., 40 of them being enlisted in ESI’s "most cited paper" and
“hot paper” lists. Many of his major inventions and patents have been converted
into commercial technology and products. In 2011, he accepted a full-time
professorship by Shaanxi Normal University and Dalian Institute of Chemical
Physics, Chinese Academy of Sciences in 2012. He is now the director of Shaanxi
Engineering Lab for Advanced Energy Technology, Shaanxi Key Laboratory for
Advanced Energy Devices and Institute for Advanced Energy Materials, Shaanxi
Normal University and Associate Director of Solar Energy Department, Dalian
National Laboratory for Clean Energy. He is also an Editorial Board Member for ACS
Sustainable Chemistry & Engineering, J. Energy Chemistry, NanoSelect and Scientific
Report. He is selected as the top 1% most highly cited author by RSC and
Clarivate Analytics. His H-index is 78 and i10-index 250.