  The synthesis of metal sulfide nanocrystals is a crucial step in the
fabrication of quantum dot (QD) photovoltaics. Control over the quantum dot
size during synthesis allows for precise tuning of their optical and electronic
properties, making them an appealing choice for electronic applications. This
flexibility has led to the implementation of quantum dots in both
highly-efficient single junction solar cells and other optoelectronic devices
including photodetectors and transistors. Most commonly, metal sulfide quantum
dots are synthesized using the hot-injection method utilizing toxic, and air-
and moisture sensitive sulfur source: bis(trimethylsilyl) sulfide (TMS)2S.
Here, we present bis(stearoyl) sulfide (St2S) as a new type of air-stable
sulfur precursor for the synthesis of sulfide-based QDs, which yields uniform,
pure, and stable nanocrystals. Photovoltaic devices based on these QDs are
equally efficient as those fabricated by (TMS)2S but exhibit an enhanced
operational stability. These results highlight that St2S can be widely adopted
for the synthesis of metal sulfide quantum dots for a range of optoelectronic
applications.
