报告一：Halid Perovskites: The New Wonder Photovoltaic Material

报告人：Tze-Chien Sum, Nanyang Technological University, Singapore

时 间：2016年6月13日（星期一），上午9:30

地 点：南楼2层会议室

摘要：

Organic-Inorganic halide perovskite solar cells are presently the forerunner amongst the solution-processed photovoltaic technologies – with efficiencies exceeding 22%. In this talk, I will review the photophysical mechanisms of the workhorse CH3NH3PbI3 system. In addition, I will highlight some of our latest findings in perovskite single crystals and low-dimensional perovskites (i.e., core-shell perovskite nanocrystals and nanoplatelets). Other novel properties of this amazing family of materials beyond the CH3NH3PbI3 system will also be featured.

报告人简介：

Dr. Tze-Chien Sum is an Associate Professor at the Division of Physics and Applied Physics, School of Physical and Mathematical Sciences (SPMS), Nanyang Technological University (NTU) where he leads the Femtosecond Dynamics Laboratory. He received his Ph.D. in Physics from the National University of Singapore (NUS) in 2005, for the work in proton beam writing and ion-beam spectroscopy. His present research focuses on investigating light matter interactions; energy and charge transfer mechanisms; and probing carrier and quasi-particle dynamics in a broad range of emergent nanoscale and light harvesting systems. Dr Sum received a total of 11 teaching awards from NUS and NTU, including the coveted Nanyang Award for Excellence in Teaching in 2006 and the 2010 SPMS Teaching Excellence Honour Roll Award. Most recently, he received the 2013 SPMS Young Researcher Award; the Institute of Physics Singapore 2014 World Scientific Medal and Prize for Outstanding Physics Research; the 2014 Nanyang Award for Research Excellence (Team); and the 2015 Chemical Society of Japan Asian International Symposium Distinguished Lectureship Award. More information can be found at http://www.ntu.edu.sg/home/tzechien/spms/index.html

报告二：Engineer Lead-Free Perovskite for Coherent Light Emission

报告人：Guichuan Xing, Nanjing Tech University (China)

时 间：2016年6月13日（星期一），上午10:30

地 点：南楼2层会议室

摘要：

Low-temperature solution-processed perovskites have recently demonstrated great potential for light emtting applications. Low threshold amplified spontaneous emission (ASE) and high Q lasing at 400 – 800 nm wavelengths have been demonstrated with perovskite thin films and micro/nano-structures, respectively. Recently, the external quantum efficiencies (EQE) of perovskite light emitting diodes have dramatically improved from <1% back in 2014 to >8%. However, such lead-based perovskites face the same toxicity concerns that had plagued their application in photovoltaics. Furthermore, the slow-bimolecular recombination in lead-based perovskites that spurs efficient photovoltaic operation is a fundamental limitation towards improving the light emitting properties. Here, we reveal the lead-free tin-based perovskites as a new and superior gain media that can overcome the abovementioned barriers. The bimolecular recombination constants of the tin-based perovskites are 2-3 orders larger than their leaded counterparts. This remarkable class of materials yields stable coherent light emission at strikingly low thresholds. Solution-proccesability allows for infiltration into natural photonic crystal corrugations in butterfly wing scales to achieve ~1 mm lasing. These attractive characteristics stem from the large absorption coefficients, high bimolecular recombination, suppressed defect densities and slow Auger recombination. Large range straightforward coherent light emission spectral tunability is demonstrated. The emission can be tuned from visible to NIR (over 1μm), which is inaccessible by their leaded counterparts. Importantly, these materials with good charge transport characteristics may hold the key to realizing electrically-driven NIR lasing with solution-processed semiconductors and will open up new avenues in perovskite light emitting devices.

报告人简介：

Dr. Guichuan Xing is currently a professor in Nanjing Tech University (China). He received his BS degree in Illuminating Engineering and Light Sources from Fudan University (China, 2003), and Ph.D degree in Physics from National University of Singapore (NUS) (Singapore, 2011). After Ph. D, he worked as a research fellow with Prof. Tze Chien Sum in Nanyang Technological University (NTU) from 2011 to 2014. His research interest includes developing and applying ultrafast nonlinear spectroscopic techniques to probing, understanding and controlling the fundamental charge and energy carrier generation, transport and relaxation processes in novel optoelectronic systems for energy storage/conversion and light emission applications.