Lithium Salt-Doped Organic Conjugated Hole Transport Layer for High-Performance PbS Quantum Dot Solar Cells

The electrical properties of hole transport layers (HTL) are critical factors for the high performance of lead sulfide quantum dot solar cells (PbS CQDSCs). Herein, the impacts of doping the organic HTL PTB7-Th with lithium bis(trifluoromethanesulfonimide) (LiTSFI) on the performance of quantum dot solar cells are explored and a notable enhancement in the fill factor is observed. A series of analytical characterizations of the doped HTLs are performed and it is found that doping with LiTFSI significantly deepens the Fermi level of the HTL, thereby improving the charge separation ability within the devices. Additionally, the conductivity of doped HTL is also improved. By optimizing the doping conditions, the doped device achieves a maximum power conversion efficiency of 12.68%. This doping strategy of organic HTL promotes the development of lead sulfide quantum dot solar cell techniques.