用于高性能硫化镉敏化太阳能电池对电极的硫化铜/还原氧化石墨烯纳米复合材料的合成

摘要

用一釜水热合成法制备了硫化铜/还原氧化石墨烯纳米复合材料,改变前驱体中石墨烯含量,得到具有不同石墨烯含量的纳米复合材料.所制备的纳米复合材料首先和聚偏氟乙烯粘结剂混合,再涂覆在SnO2x-Fx基体上,得到以CdS敏化TiO2为负极的量子点太阳能电池的对电极,并与传统的Cu2S/Cu对电极进行比较.用场发射扫描电子显微镜、X-射线衍射、拉曼光谱、循环伏安和阻抗谱技术表征了纳米复合材料对电极的微观结构和性能.结果表明:硫化铜/还原氧化石墨烯纳米复合材料优于Cu2S/Cu对电极.前驱体中石墨烯的含量显著影响了硫化铜纳米晶的化学计量比和形貌.当前驱体石墨烯含量在中等水平下,获得了具有更多供Sx2-离子还原的活性位的优化的硫化铜/还原氧化石墨烯纳米复合材料.以此优化的纳米复合材料为对电极制备的量子点太阳能电池在100 mW/cm2的光照强度下具有高的、稳定的和可重复的2.36％的能量转化效率,高于用Cu2S/Cu为对电极的能量转化效率.此性能的提升归因于硫化铜纳米晶和导电的还原氧化石墨烯之间的协同作用,还原氧化石墨烯充当共催化剂和导电促进剂,降低对电极的内阻并加快多硫化物的还原.%Copper sulfide (CuxS)/reduced graphene oxide (RGO) nanocomposites were prepared by a one-pot hydrothermal method with various contents of GO in the initial precursor.The nanocomposites were first blended with a polyvinylidene fluoride binder,then coated onto SnOx2-Fx substrates,which were used as the counter electrodes (CEs) of quantum dot solar cells (QDSCs)using a CdS-sensitized TiO2 as a photoanode.The microstructure and performance of the CEs were characterized by FE-SEM,XRD,Raman spectroscopy,cyclic voltammetry and electrochemical impedance spectroscopy.Results show that the CuxS/RGO CEs are superior to the conventional Cu2S/brass CE.The stoichiometry and morphology of the CuxS nanocrystals are significantly influenced by the initial GO content in the precursor.A CuxS/RGO nanocomposite with more active sites for effective Sx2-ion reduction in a polysulfide electrolyte (S2-/S2x-) is optimally obtained at a medium GO content in the precursor.The QDSC assembled with the optimized CuxS/RGO CE exhibits a reproducible high and stable power conversion efficiency of 2.36％ under an illumination intensity of 100 mW/cm2,which is higher than the value (1.57％) of the cell with the Cu2S/brass CE.The improved performance is attributed to the synergistic effect between the CuxS nanocrystals and conductive RGO in the CuxS/RGO CE,where RGO acts as both a co-catalyst to accelerate the polysulfide reduction and a conductivity promoter to decrease the series resistance of the CE.