Core/Shell/Shell Strategy for Stable and Luminescent PbSe Colloidal Nanocrystals Tuned through the Extended Short- to Mid-Wave Infrared.

Despite their ideal exciton energies, implementation of colloidal lead selenide (PbSe) nanocrystals into extended short- to mid-wave infrared (eSWIR to MWIR) optoelectronic devices has been limited due to their chemical instability in air and insufficient colloidal stability at sizes large enough (diameter of >13 nm) to reach this spectral range. To address this, we investigate Pb chalcogenide core/shell/shell nanocrystals with a PbSe core, a first shell of PbS, and a second surface-layer shell of PbClx (PbSe/PbS/PbClx core/shell/shell), to produce nanocrystals tunable within the eSWIR to MWIR (λ = ∼2.2-3.1 μm) region with notable increases in the photoluminescence quantum yield (>4×) and both colloidal and air stability compared to core-only PbSe nanocrystals. The PbS/PbClx shell/shell is ∼1-2 nm thick and results in a red shift of the nanocrystal exciton energies. This work improves the viability of solution processed thin-film eSWIR and MWIR PbSe colloidal nanocrystal photodetectors, sensors, and light sources.