Free and localised exciton of ternary nanocrystals in CsX-PbX2 thin films (X = Cl, Br, I)

Abstract The creation of Pb2+-based ternary nanophases was evidenced in co-evaporated CsX-PbX2 (X = Cl, Br, I) thin films using X-ray diffraction spectroscopy (XRD). The optical properties of CsPbX3 and Cs4PbX6 nanostructures were determined. CsPbX3 (X = Cl,Br) are wide gap semiconductors with direct band transitions and a pronounced Wannier free exciton emission showing subnanosecond decay times and very small Stokes-shift. On the contrary, it is supposed that, in CsPbI3, the auto-localization of the exciton state results in a broad and much slower emission with large Stokes shift. Cs4PbX6 is characterized by the auto-localized exciton emission in the near UV/violet spectral region and two component decay kinetics closely similar to that of Pb2+ emission centers in KX:Pb2+ (X = Cl, Br, I).