Doped Organic Hole Extraction Layers in Efficient PbS and AgBiS₂ Quantum Dot Solar Cells

The efficiency of PbS quantum dot (QD) solar cells has significantly increased in recent years, strengthening their potential for industrial applications. The vast majority of state-of-the-art devices utilize 1,2-ethanedithiol (EDT)-coated PbS QD hole extraction layers, which lead to high initial performance, but result in poor device stability. While excellent performance has also been demonstrated with organic extraction layers, these devices include a molybdenum trioxide (MoO3) layer, which is also known to decrease device stability. Herein, we demonstrate that organic layers based on a poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) polymer doped with C60F48 can serve as hole extraction layers for efficient EDT-free and MoO3-free QD solar cells. Such layers are shown to offer high conductivity for facile hole transport to the anode, while effectively blocking electrons due to their low electron affinity. We show that our approach is versatile and is applicable also to AgBiS2 QD solar cells.