报告题目：Si based down-conversion layer for solar cell efficiency improvement 

　　主讲嘉宾：Assoc. Prof. Labbé Christophe  

　　　　　　　CIMAP Laboratory, Caen , Normandy, France 

　　　　　　　CNRS/CEA/ENSICAEN/Unicaen 

　　时　  间：11月28日（周三）10:00-11:30 

　　地　  点：李薰楼356会议室 　

　　报告简介 

　　After a brief presentation of the CIMAP (Research Center on Ions, Materials and Photonic), an introduction of the different subjects of my team "NIMPH" (Nanomaterials, Ions and Metamaterials for Photonics) is proposed. I will particularly focus my presentation on the down-converter layers based on rare earth doping to improve the efficiency of the solar cells. 

　　Indeed, one promising solution to increase the solar cells efficiency consists in developing down-converter layers compatible with the silicon industry which absorb UV photons and convert them into IR ones. To achieve such a goal, rare earth (RE) ions doped silicon nitride-based thin films have been deposited by reactive magnetron co-sputtering. This nitride host matrix allows a high RE ions incorporation while avoiding the clustering effect observed in silicon oxide matrices. Moreover, it has been used as an efficient antireflective layer contributing also to a better efficiency of the Si solar cells. Two different co-doping with RE ions have been chosen i.e. Tb³⁺-Yb³⁺ and Ce³⁺-Yb³⁺. 

　　The first step of this work is focused on achieving an intense emission of Tb³⁺ or Ce³⁺ ions by optimizing the deposition parameters. In the case of Tb³⁺ ions, the goal is to enhance the coupling between sensitizers and Tb³⁺ ion activator, whereas in the case of Ce³⁺ ions, the optimized 4f-5d transitions allow achieving a direct efficient excitation of the RE ions. A comparison between the excitation efficiency of each co-doped system will be presented. 

　　The second step consists in the incorporation of Yb³⁺ ions with an increasing content to optimize the Tb³⁺/Ce³⁺-Yb³⁺ ions coupling with the aim at obtaining an intense emission at 980 nm just above the Si fundamental band gap. The excitation mechanisms of Tb³⁺ and Yb³⁺ ions will be discussed. Furthermore, the IR quantum cutting efficiency will be determined by photoluminescence decay time measurements (above 180%). 

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