Luminescent CulnSe2-Based Core/Shell Nanocrystals: Characterizing Defects in CulnSe2 Nanocrystals
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As interest continues to grow in new materials for next-generation photovoltaic (PV) devices (i.e. solar cells), it is important to understand the mechanisms and limitations of promising materials. Many researchers are focused on the use of semiconductor nanocrystals (NCs) in PV devices because of their potential to be deposited in thin films via solution, which is more cost-effective than traditional methods. This study focuses on CuInSe2 (CISe) NCs, which are part of a larger class of materials known as CuInxGa1-xSe2 (CIGS). CIGS is well-known in the PV industry, especially for its use on flexible substrate materials, which have significant cost and processing advantages over traditional, bulky, glass-based solar cells. However, defects within or on the surface of the CIGS NCs limit the movement of holes and electrons, affecting the ability of the NCs to extract charge carriers; these defects ultimately result in lower-efficiency PV devices. The purpose of this study is to better understand the defects within CISe NCs by coating them with ZnS shells. A Zn-based shell was successfully formed around a CISe NC without compromising the integrity of the CISe NC. The shell also successfully passivated the surface defects and increased the efficiency of the CISe NCs. By creating luminescent CISe-based core/shell NCs, this study examines the nature of CISe NC defects and the implications of these defects on the future of CISe in the PV industry.