Topic 1: Solution Processed Thin Film Photovoltaics
Solution processed thin film photovoltaics has attracted substantial attention, due to its great potential of realizing low-cost and high performance solar technology. This talk will focus on solution processed thin film photovoltaics based on the organic-inorganic hybrid (CH3NH3PbX3) materials and inorganic materials (e.g. Cu2ZnSn(S,Se)4). The development of solar cell technologies toward high power conversion efficiency requires delicate control over the film growth, the engineering of relevant interfaces, and deep understanding of materials property and device physics. Here, both CH3NH3PbX3 and Cu2ZnSn (S,Se)4 are demonstrated with high performance through control the film formation, defect passivation and interface engineering. Take CH3NH3PbX3 as an example, the carrier dynamics through the entire perovksite solar cell was well controlled, which leads to suppressed carrier recombination in the absorber, efficient carrier injection into the carrier transport layers, and good carrier extraction at the electrodes, and eventually the highly efficient power conversion efficiency (approaching 20%). The approach on the optimization of material quality and interface property could be extended to the development of other semiconductor materials, which benefits their applications in photovoltaics, transistors, light emitting diodes, memories, sensors, and etc.
Topic 2: Exploration of organic-inorganic hybrid materials and its optoelectronic applications
The success of the optoelectronic devices in modern life is ultimately dependent on the exploration of low cost and high quality materials, via ease processing, including synthesis in nano-scale, thin-film growth in sub-micro-scale, and device design and system integration in macro-scale. Recent advances in optoelectronic devices, particularly photovoltaics (PVs), have identified the organic-inorganic hybrid perovskite (CH3NH3PbI3) materials from the conventional organic or inorganic semiconductors, as its extreme low-cost, and unprecedented rapid increase in power conversion efficiency (20% within 5 years of development) that is faster than any other material in solar cell history. This led to an explosion of the study on the origin of the unique materials property and the pursuit of the pathway toward high performance photovolatics, as well as other applications beyond. In my future work, I will leverage the characteristics of both inorganic materials (ionic or covalent interaction) and organic materials (hydrogen bonding and van der Waals interaction), to continuously create a composite with enhanced properties relative to combine the useful properties of the two components within a single material. Project will be initiated with the development of the hybrid materials that consists desired elements (e.g. environmental friendly elements), with high thermal/environmental stability, and continue by demonstrating the improved photovoltaic performance and potential applications of other electronics, e.g. LED, FET. These high performance optoelectronic devices can be further integrated with existing functional devices, to explore its application in artificial photosynthesis through constructing tandem devices, and wearable electronics based on its flexibility.
Dr. Huanping Zhou holds a BS in Material Chemistry from the China University of Geosciences in 2005, and she received her Ph.D. in Inorganic Chemistry from Peking University in 2010 (Advisor: Prof. Chunhua Yan). After that, she joined UCLA as a postdoctoral research from 2010 to 2015 (Advisor: Prof.Yang Yang). She is a materials chemist with expertise in the fields of nanoscience, thin film optoelectronics, organic/inorganic interface engineering, and the development and fabrication of related devices, such as photovoltaic cells, TFTs, etc. Her major contributions to the field of thin film photovoltaics are an improved understanding of thin film growth, defects passivation of polycrystalline film, and interface engineering, and its influence on device performance; the benign solvent processed CuIn(S,Se)2/Cu2ZnSn(S,Se)4 solar cell, solution processed window layer and top electrode, novel film growth and interface engineering for perovskite solar cell. She demonstrated 19.3% power conversion efficiency for perovskite solar cell by interface engineering and improved crystal growth process. Also, she involved in achieving approximately 12% PCE and 9% PCE for CIGS and CZTS solar cell based on solution- phase precursor system. In addition to thin film optoelectronics, she also contributed to the area of functional nanomaterials, including controllable synthesis, self-assembly, and surface modification. She has published more than 46 papers in high quality peer-reviewed journals, e.g. Science, Nature Nanotech., Nature Commun., J. Am. Chem. Soc., Adv. Mater., Nano Lett., etc. She also received a variety of awards, e.g. Excellent Doctoral Dissertation (PKU), and 2014 Chancellor's Postdoctoral Scholar Award (UCLA).