Investigation on CuxS nanoparticles based hole transfer layer as an inexpensive alternative for next generation solar cells

The usage of expensive organic hole transfer layer (HTL) such as Spiro-MeOTAD and the necessary additives (Li-TFSI salt and tert-butyl pyridine) for the enhanced charge carrier conductivity are the factors limiting the conventional perovskite solar cells (PSCs) in delivering stable device performance. Hence, in this work, the colloidal copper sulfide (CuxS) nanoparticles were utilized as an inexpensive alternative for the conventional Spiro-MeOTAD HTL through simple solution processing method. The CuxS HTL was deposited onto the perovskite layer by spin coating method using colloidal CuxS NPs ink, followed by the solid-state ligand exchange approach. Since, the CH3NH3PbI3 layer is highly prone to degrade with inappropriate solvents, special attention has been paid while fabricating colloidal CuxS NPs based HTL through solution processing. The cross-sectional SEM analysis confirms the successful incorporation of CuxS HTL without deterioration of the perovskite thin film. The device performance of conventional and CuxS HTL based perovskite solar cells were analysed through the current density-voltage (J-V) characteristics with the aid of simulated solar light irradiation.