Quantum dots for photovoltaics: a tale of two materials

Quantum dot (QD) solar cells, benefiting from unique quantum confinement effects and multiple exciton generation, have attracted great research attention in the past decades. Before 2016, research efforts were mainly devoted to solar cells comprising lead chalcogenide QDs, while lead halide perovskite QDs have recently emerged as a rising star in the field. This review aims to compare similarities and differences between lead chalcogenide and lead halide perovskite QDs for photovoltaic applications. The fundamental physical properties of these two types of nanomaterials and their state-of-the-art photovoltaic devices are summarized, with a focus on ligand and device engineering. Furthermore, a special section is devoted to the stability issue that often hinders photovoltaic technologies. Finally, future development in tandem devices, challenges associated with large-size cell fabrication and lead toxicity, and potential mitigation solutions are discussed.