Signatures of Energy Transfer in Solid Films of CuInS₂ Colloidal Quantum Dots

Energy transfer (ET) is a process that can dramatically enhance or obstruct performance of devices based on colloidal quantum dot (QD) films. For cadmium and lead chalcogenides, the influence of ET on exciton dynamics of the QD films is well understood owing to a large body of experimental and theoretical work. On the other hand, the studies of the impact of ET on the properties of ternary and quaternary QDs such as CuInS2 or Ag-In-Zn-S are in their infancy. It is important to fill this gap as ternary and quaternary QDs are emerging as exciting candidates for many applications relying on the deposition of the QD films. In this work, we demonstrate spectroscopic signatures of ET in films deposited from inhomogeneous ensembles of CuInS2 QDs. Using the experimentally obtained parameters, we evaluate the ET rates and find that their values are similar to those found for PbS QD films. We argue that the consequences of our findings should inspire future investigations.