Investigation into the Photoluminescence Red Shift in Cesium Lead Bromide Nanocrystal Superlattices

The formation of cesium lead bromide (CsPbBr3) nanocrystal superlattices (NC SLs) is accompanied by a red shift in the NC photoluminescence (PL). The values of the PL red shift reported in the literature range from none to similar to 100 meV without unifying explanation of the differences. Using a combination of confocal PL microcopy and steady-state optical spectroscopies we found that an overall PL red shift of similar to 96 meV measured from a macroscopic sample of CsPbBr3 NC SLs has several contributions: similar to 10-15 meV from a red shift in isolated and clean SLs, similar to 30 meV from SLs with impurities of bulklike CsPbBr3 crystals on their surface, and up to 50 meV or more of the red shift coming from a photon propagation effect, specifically self-absorption. In addition, a self-assembly technique for growing micron-sized NC SLs on the surface of perfluorodecalin, an inert perfluorinated liquid and an antisolvent for NCs, is described.