Electrochemical and atomic force microscopy investigations ofthe effect of CdSon the local electrical properties of CH3NH3PbI3:CdS perovskite solar cells
Mingxuan Guo, Fumin Li, Lanyu Ling, Chong Chen*
The effect of the incorporated CdS on the local optoelectronic properties of CH3NH3PbI3:CdS bulk heterojunction (BHJ) perovskite solar cells (PSCs) are studied using Kelvin probe force microscopy (KPFM), conductive atomic force microscopy (c-AFM) and electrochemical impedance spectroscopy (EIS). KPFM and c-AFM results clearly show that, as the amount of incorporated CdS increases, the incorporated CdS creates more uniform and compact perovskite films. Moreover, the incorporated CdS nanoparticles lead to a higher surface potential and a more uniform and higher photocurrent distribution on the CH3NH3PbI3:CdS active layer, which indicates that CdS nanoparticles can lead to a more effective photo-generated electrons transfer from the CH3NH3PbI3to the CdS and proves experimentally that the CdS nanoparticles can form a continuous photo-generated electron transport channel. EIS results show that the CdS can effectively decrease the contact resistances at active layer/electron transport layer and active layer/hole transport layer interfaces and helps in the charge collection of the cells, which further confirms that the CdS nanoparticles can play the role of transporting electrons. Our study provides a nanoscale understanding of the improved device performance of CH3NH3PbI3:CdS PSCs.