Thermal Annealing Effects of Plasmonic Cu1.8S Nanocrystal Films and Their Photovoltaic Properties

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• 作者：Lige Liu ; Bin Zhou ; Luogen Deng ; Wenping Fu ; Jiatao Zhang ; Min Wu ; Wenhua Zhang ; Bingsuo Zou ; Haizheng Zhong
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：November 20, 2014
• 年：2014
• 卷：118
• 期：46
• 页码：26964-26972
• 全文大小：462K
• ISSN：1932-7455

文摘

Colloidal Cu_2鈥?i>xS nanocrystals are potential abundant, low-cost, and environment-friendly candidates for photovoltaic and photothermal applications. The fabrication of high-quality nanocrystal films through a solution process is a key step toward the exploration of their applications. In this work, we fabricated high-quality Cu_1.8S nanocrystal films, characterized their phase transformation under thermal annealing treatments, and investigated the evolution of the corresponding optical and electrical properties. It was demonstrated that the Cu_1.8S nanocrystal films undergo a phase transformation from metastable rhombohedral phase to stable tetragonal phase (Cu₂S) after annealing at a temperature higher than 240 掳C, which is much lower than that of the bulk materials (544 掳C). Along with the transformation, both optical and conductivity properties exhibit well-defined evolution from nonstoichiometric semiconductor to stoichiometric semiconductor, which can be interpreted through a combined electronic structure analysis and theoretical modeling. The correlations between the crystal structure, composition, optical and electrical properties enable us to gain further insights into the structure鈥損roperty relationship in Cu_2鈥?i>xS nanocrystals. More importantly, a highly conductive Cu_2鈥?i>xS nanocrystal film with electrical conductivity up to 6.7 S/cm was obtained, implying the potential to be used as conductive electrodes. We further integrated the annealed Cu_2鈥?i>xS nanocrystal films into a photovoltaic device by adopting a FTO/TiO₂/Cu_2鈥?i>xS:CdS/MoO₃/Au structure, and a preliminary power conversion efficiency of 0.24% was achieved.