  Light-harvesting devices made from PbS quantum dot (QD) absorbers are one of
the many promising technologies of third-generation photovoltaics. Their
simple, solution-based fabrication together with a highly tunable and broad
light absorption makes their application in newly developed solar cells
particularly promising. In order to yield devices with reduced voltage and
current losses, PbS QDs need to have strategically passivated surfaces, most
commonly achieved through lead iodide and bromide passivation. The interdot
spacing is then predominantly filled with residual amorphous lead halide
species that remain from the ligand exchange, thus hindering efficient charge
transport and reducing device stability. Herein, we demonstrate that a
post-treatment by iodide based 2-phenylethlyammonium salts (X-PEAI) and
intermediate 2D perovskite formation can be used to manage the lead halide
excess in the PbS QD active layer. This treatment results in improved device
performance and increased shelf-life stability, demonstrating the importance of
interdot spacing management in PbS quantum dot photovoltaics.
