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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 ∼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 ∼96 meV measured from a macroscopic sample of CsPbBr3 NC SLs has several contributions: ∼ 10-15 meV from a red shift in isolated and clean SLs, ∼ 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.
Baranov et al. (Thu,) studied this question.