Synthesis And Properties Of Copper Selenide And Composite In Quantum Dots-sensitized Solar Cells

With the increasingly prominent energy issues and environmental problems,the development of clean energy is undoubtedly the most effective way to solve these problems.Among the kinds of new energy devices,quantum dot sensitized solar cells（QDSSCs）have been considered as one of the most potential way due to their unique advantages.However,compared to dye sensitised solar cells（DSSCs）which are developed,the power conversion efficiency of QDSSCs is still under a very low stage and far from their ideal theoretic level.Hence the commercial development is limited.One of the very important reasons for this low efficiency is the lack of suitable counter electrodes（CEs）.As a very essential part of the solar cells,it is in urgent need to develop high efficient CEs with low cost and stable performances.Based on the understanding of the developments of CEs,in this study,we develop a new method to synthesize novel nanostructure Cu_2-XSe,Cu_1.8Se and further Cu_1.8Se/C composite materials at room temperature.Firstly,a high surface area Cu_2-XSe materials with a nanotube structure composed by ultrathin sheets was synthesized according to the ion exchange process,and the formation mechanism has been detailed studied.Subsequently,the materials were fabricated to CEs by direct coating process and then it was applied into the QDSSCs,furthermore,its electrochemical performances were investigated.The data indicated that the QDSSCs with Cu_2-XSe CEs achieved a high efficiency of 5.14%,which was superior to that of most common used Cu₂S/Brass and Pt electrodes.These high performances can be attributed to the high surface area,the high electronic conductive performance and high catalytic activities,which can afford more active sites,speed up the electron transmission and reduce the electrilytes.To further improve the performance of QDSSCs,a 1 D arrays nanostructure with hollow tube of Cu_1.8Se was in-situ fabricated according to sacrificing template method,and also,this material was applied as CEs into the QDSSCs,and the as-prepared solar cells displayed the most high performance with an efficiency of 4.48%(J_SC=17.76 mA cm^-2,V_OC=0.549 V,FF=0.46).what’s more,based on a rationally fabrication,the Cu_1.8Se/C composite materals were synthesized by CVD method,the QDSSCs with this CE also displayed a high efficiency（4.77%）due to the very low resistance of CEs supported by the C.