报告题目：Engineering of Chemical Coordination and Opto-Electronic Properties of High-Performance Perovskite Solar Cells

时 间：2017年4月1日10:30-11:30

地 点：光电国家实验室A101

报 告 人：Prof. Jian-Bin Xu, The Chinese University of Hong Kong

报告人简介：

Dr. Xu received his B.Sc. and M.Sc. from Nanjing University in 1983 and 1986, respectively, in Physics and Electronic Science and Engineering, under the supervision of Prof. Shu-yi Zhang (Member of Chinese Academy of Sciences). Since 1988, he was highly privileged to study in the University of Konstanz (an elite university), particularly under the supervision of Prof. Klaus Dransfeld (Member of German Academy of Sciences), former Director of Max-Plank Institute for Solid State Research, and Max-Plank Institute for High-Magnetic Fields). His doctoral dissertation was focused on the near-field sensing and nanoscopic energy transfer and heat transport associated with electronic processes. He earned his doctorate (Dr.rer.nat.) in 1993. Afterwards, he joined the Department of Electronic Engineering, The Chinese University of Hong Kong. He has been Professor in the department since the midst of 2002.

Dr. Xu has published extensively on advanced electronic and photonic materials and devices as well as on nanotechnology in peer-reviewed professional journals (c.a. 240) and conferences (c.a. 50) as well as more than 200 presentations, including conference invited talks, colloquia, seminars, etc. The published papers have been extensively accessed and cited, as well as many topic reviews and monographs, and patents. Meanwhile, he has secured numerous competitive research grants. Also he actively participates in a myriad of professional activities and has served as symposium chair in several international conferences. Particularly, he has served as Member of International Advisory Committee, International Conference on Nanoscience and Technology, China 2009 (ChinaNano 2009), and as Director of Advanced Study Institute on Printed Electronics 2013 (Dedicated to Professor Sir Charles Kao on the Occasion of his 80th Birthday). He is Fellow of Hong Kong Institution of Engineers, Senior Member of IEEE, the Secretary and Council Member of Hong Kong Materials Research Society, and Member of American Physical Society, Materials Research Society, Hong Kong Institution of Science, and Physical Society of Hong Kong. Since 2007, he has been Director of Materials Science and Technology Research Center in CUHK. From 2011, he has been Convener of Strategic Initiatives for Nano, Energy, and Materials in CUHK.

Dr. Xu is a recipient of Joint Research Fund for Overseas Chinese, Hong Kong and Macau Scholars, funded by NSFC, a nationally prestigious award (formerly National Science Fund for Distinguished Young Scholars (Overseas Chinese)).

报告摘要：

In this talk, I will present the advances of high-performance perovskite solar cells (PSCs) by our group in the past few years. Firstly, I will report our effort on significantly improving the stability of the perovskite thin films by developing a reliable nonstoichiometric acid-base reaction (NABR) route towards the stable perovskite. Secondly, I will demonstrate the improved stability, scalability and feasibility of PSC fabrication, via realizing an expeditious deposition using dilute CH₃NH₂ gas for high-quality CH₃NH₃PbI₃, which is based on CH₃NH₂+HPbI₃ (gas + solid) reaction. CH₃NH₂-rich and textured perovskite thin films can be intentionally produced. We find that slight CH₃NH₂-rich species induce to form cross-linkage and texture among crystals. In addition, slight MA-rich composition can passivate vacancy sites to resist H₂O penetration, thus leading to two-month stability under ~65% humidity. The PSCs deliver maximum efficiency up to 18.4% after one month storing.

Thirdly, I will present a simple intermediate halide exchange process (HEP) using nonstoichiometric CH(NH₂)₂I/HPbI₂Br to produce high-quality CH(NH₂)₂PbI_3-xBr_x with crystal domain size up to 2-3 μm. The unstable HPbI₂Br intermediate facilitates the halide exchange by FAI and the conversion to FAPbI_3-xBr_x perovskite (x~0.44). Also excess impurity releasing promotes the crystallization process. PSCs produced by HEP exhibit efficiency as high as 19.0% without appreciable hysteresis.

Fourthly, besides the ion exchange during crystallization process, we introduce a facile dual ion exchange (DIE) method, treating trigonal phase FAPbI₃ thin film surface with MABr/tert-butanol solution for 10 s, to replace the traditional directly mixing (DM) method and obtain the mixed perovskite thin film with optimized band gap. In this process, the crystal phase set-up and guest functional ions introduction are independant, eliminating the phase competition between different perovskite components. The excess MA⁺ and Br⁻ ions could fill the vacancies at grain boundary first and then exchange some FA⁺ and I⁻ homogeneously, demonstrating high solar cell PCE up to 18.1%, enhanced moisture and illumination stability as well as reduced hysteresis.

Finally, I will briefly discuss the light-absorption enhancement by utilizing a molecule/polymer binary HTM with periodic microstructure. We find that the quasi periodic microstructure composite (PMC) HTM with conformal Au electrode can promote the absorption through the enhanced cavity effects. This PMC PSC affords a high efficiency up to 17.7% with enhanced short circuit current.