| Lecturer Profile |
Prof. CAO Guozhong received his Ph.D. degree from Eindhoven University of Technology, Eindhoven, the Netherlands. He received his MS and BS degree respectively Chinese Academy of Sciences, Shanghai Institute of Ceramics, and East China University of Science and Technology, China. Currently, Dr. CAO is Boeing-Steiner professor of Materials Science and Engineering, professor of Chemical Engineering and adjunct professor of Mechanical Engineering at the University of Washington, Seattle, WA, and also a professor at Xidian University, China, a senior professor at Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, and a professor at National Center for Nanoscience and Technology (NCNST), China. He has published over 450 technical papers with over 320 in archive journals and authored and edited 7 books, and is one of the Thomson Reuters Highly Cited Researchers (h-index: 65). His current research focused on chemical processing of nanomaterials for solar cells, batteries, and super capacitors as well as actuators and sensors. |
| Lecture Abstract |
Organometallic halide perovskite materials have a variety of remarkable optoelectronic properties, such as suitable band gap (1.5eV), high absorption coefficient, long carrier diffusion lengths and lifetimes. All these unique characters pave the way for perovskite-based devices, especially the photovoltaic cells. Its conversion efficiency have surged to 20.1% in several years and perovskite solar cells have been viewed as the new generation high efficiency thin-film cells at low cost. In this seminar, I will talk about (1) the study of charge transfer and surface potential as a function of surface morphology of TiO2 compact layer, (2) control the morphology of TiO2 compact layer, and (3) control of the perovskite film morphology with the specifics detailed below.
The variation of the surface potential, photo-generated voltage, and photocurrent networks of the perovskite solar cells (PSCs) with different film topography has been studied by coupling scanning Kelvin probe force microscopy (SKPM) and photoconductive atomic force microscopy (pcAFM). These results suggest that the performance of PSCs can be improved through better control of morphology.
A series of TiO2 compact films was prepared by sol-gel method with different sol aging time resulting in change of, thickness, surface roughness and compactness. High roughness of the films benefits the light absorption of perovskite layer and the injection efficiency at interface. The films with better compactness perform better hole blocking effect. The Ag@TiO2 nanoparticles made by polyol solution method are embedded in perovskite films, resulting in an enhanced short-circuit current density due better light absorption and reduced charge recombination.CH3NH3Cl was introduced into the pristine CH3NH3PbI3 precursor for antisolvent precipitation at low temperature and fabricated high quality perovskite films with desired morphology, crystallinity and optical properties. CH3NH3Cl exerted significant impacts on the perovskite crystallization process by controlling the delivery speed of PbI2 from the intermediate phase CH3NH3I2Cl. The resultant solar cells demonstrated an average power conversion efficiency around 16.63% and a best efficiency at 17.22% under the standard light illumination condition. |
