CuSx hole transport layer for PbS quantum dot solar cell

Abstract

Lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs) are emerging photovoltaic technology due to their outstanding light-harvesting ability in the visible and near-infrared spectral region, long-term air stability, multiple exciton generation and solution processability. However, PbS CQDSCs have been limited by the unsatisfactory carrier collection in the CQD films. Band alignment engineering using p-type hole transport layer (HTL) was proved to efficiently promote the carrier collection in cells with both planar and ordered bulky heterojunctional (OBH) structures. Nevertheless, seeking for proper p-type materials suitable for the PbS CQDSCs is still an open question. Herein, we reported a new p-type metal-organic material, CuSx, could act as HTL of PbS CQDSCs with OBH structure. The CuSx possesses a Fermi level EF (−5.02 eV), shallower valence band energy (−5.48 eV) and conduction band energy (−3.19 eV), inducing a proper band alignment at the PbS light-harvesting layer/CuSx interface. This not only enhanced hole extraction proved by the increase of short-circuit current density (Jsc) from 19.12 to 22.33 mA/cm2, but also blocked back electron demonstrated by the extended carrier lifetime. Consequently, cells with CuSx HTL generated a power conversion efficiency of 5.2%, leading to a PCE increase of 13% compared with that of reference HTL-free cell (4.6%). Our work introduced a promoting CuSx hole extraction material which shows great potential application in quantum-dot-based devices suffering from the insufficient carrier collection.