The effect of CuS counter electrode microtopography on the properties of quantum dot sensitized solar cells

The counter electrode (CE) is an essential working part in quantum dots sensitized solar cells (QDSCs), which performs the function of extracting electrons form external circuit and catalyzing the reduction of electrolyte. Usually, CuS based composite acts as CEs in QDSCs to realize the dual functions. In this work, the micro topography of CuS film on FTO glass was modified through changing preparation route and conditions to investigate the possibility of mono component CuS film as CEs in liquid junction QDSCs. Two kinds of CuS CEs were prepared on FTO conductive glass substrate through successive ionic layer adsorption and reaction (SILAR) and modified hydrothermal method, respectively. Based on the results of XRD, SEM and EDX characterization, ECS and J-V curves were analyzed to investigate the effect of CEs' particle size, microstructure and film morphology on the photovoltaic properties of QDSC samples. The results showed that CuS CEs prepared through appropriate SILAR cycle times exhibited higher catalyzing ability due to smaller diameter of CuS particles and uniform distribution of CuS particles in film, compared with those with modified hydrothermal method. CuS CEs with 10 deposition cycles showed the best catalyzing ability of the lowest charge transfer resistance (3.00 Omega) on CE/electrolyte interface and the power conversion efficiency (PCE) of QDSC consisting of this CuS CE reached 3.83%.