2D-MoS₂ nanosheets as effective hole transport materials for colloidal PbS quantum dot solar cells

Herein, we demonstrate for the first time matrix-free deposition of two dimensional (2D) MoS₂ nanosheets as an efficient hole transport layer (HTL) for colloidal lead sulfide (PbS) quantum dot (QD) solar cells. We have developed all-solution-processed n-p-p⁺ architecture solar cells where ZnO nanoparticles were used as an n-type window layer, a PbS QD layer acted as a light absorbing p-type layer and 2D-MoS₂ nanosheets acted as a p⁺-type hole transport layer. The MoS₂ nanosheets allow better interface with the PbS QD layers. The incorporation of the MoS₂ hole transport layer leads to superior fill factor, higher open circuit voltage and better performance in colloidal PbS QD solar cells. These results show that one layer of MoS₂ nanosheets improves the power conversion efficiency of the device from 0.92% for a hole transport material free device to 2.48%. The present work reveals the development of 2D-MoS₂ nanosheets as a new hole transport layer for the fabrication of cost-effective, durable and efficient colloidal PbS quantum dot solar cells.