Prospects and challenges of kesterite indoor photovoltaics

Quaternary chalcogenides, such as the kesterite Cu2ZnSnS4, were at the forefront of the thin-film photovoltaics (PVs) community, but interest waned in the 2010s as their performance stagnated and was surpassed by lead-halide perovskite (LHP) PVs in efficiency. But recently, these quaternary chalcogenides have gained a resurgence in interest as the performance bottlenecks that were in place for a decade were overcome, coupled with the growing importance of indoor photovoltaics (IPVs). Harvesting energy from ambient lighting with IPVs is widely regarded as a highly promising and sustainable approach to power the billions of autonomous electronics that are part of the Internet of Things ecosystem. Chalcogenides, such as Cu2ZnSnS4, are highly promising for IPVs because their bandgaps could be tuned toward the optimal value for indoor light harvesting (∼1.9 eV), and these materials benefit from the high stability and composition of nontoxic, earth-abundant elements, which are strong advantages over LHP IPVs. This perspective discusses the opportunities offered by using kesterites for IPVs, including their efficiency potential, as well as the challenges that need to be overcome to achieve high performance under indoor lighting.