Photovoltaic-targeted photoluminescence lifetime engineering in bright type-II alloy quantum dots

A crucial issue faced by quantum dot solar cells (QDSC) is how to achieve a quantum dot material with high photoluminescence (PL) quantum yield and long excited state lifetime at the same time to maximize charge carrier collection efficiency. Here, we present a new type of Zn0.9Cd0.1S/ZnSe hetero-nanocrystals that have a staggered band alignment, i.e., a type-II structure by which the wave function overlap between electrons and holes is reduced, thereby leading to a significant enhancement in the PL lifetime. The resultant QD also exhibits a QY up to 75.4%, which is, to the best of our knowledge, the highest one for a type-II QD to date. In particular, we explore the underlying relationship between the broad tunability and energy level alignment of these hetero-nanocrystals, and we highlight the properties that have delivered QDSCs and light-emitting diodes.