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.