Acceleration of Near-IR Emission through Efficient Surface Passivation in Cd₃P₂ Quantum Dots

Fast near-IR (NIR) emitters are highly valuable in telecommunications and biological imaging. The most established NIR emitters are epitaxially grown In_xGa_1-xAs quantum dots (QDs), but epitaxial growth has several disadvantages. Colloidal synthesis is a viable alternative that produces a few NIR-emitting materials, but they suffer from long photoluminescence (PL) times. These long PL times are intrinsic in some NIR materials (PbS, PbSe) but are attributed to emission from bright trapped carrier states in others. We show that Cd₃P₂ QDs possess substantial trap emission with radiative times >10¹ ns. Surface passivation through shell growth or coordination of Lewis acids is shown to accelerate the NIR emission from Cd₃P₂ QDs by decreasing the amount of trap emission. This finding brings us one step closer to the application of colloidally synthesized QDs as quantum emitters.