EFFECT OF DC ELECTRIC-FIELD ON PHOTOLUMINESCENCE FROM QUANTUM-CONFINED PBI2 NANOCRYSTALS

The influence of dc electric field is examined on the photoluminescenc e spectra of various PbI2 nanocrystals in a poly (vinyl alcohol) matri x, prepared by fast and slow cooling of a hot saturated aqueous PbI2 s olution. The thin flat PbI2 nanocrystals with a thickness of less than 1 nm exhibit a strong 1D quantum confinement. The application of an e lectric field of up to 16 kV cm(-1) causes a pronounced Stark effect i n the differential absorption spectrum and enhancement of excitonic ph otoluminescence. The last effect results probably from the field-induc ed detachment of surface-trapped excitons (thermoelectronic ionization or Frenkel effect). While, the larger PbI2 nanocrystals of size 5 nm did not show an appreciable field-induced effect in the photoluminesce nce spectra. Such different behaviour between large and small nanocrys tals demonstrates the dramatic influence of the surface on the exciton ic radiative recombination in semiconductor quantum dots.