Electroabsorption Spectra of Lead Sulfide (PbS) Quantum Dots in a Polymer Film

The electric field response of lead sulfide (PbS) quantum dots with near-infrared absorption of 1000-1600 nm (corresponding to diameters of 2-5 nm) embedded in a PMMA film has been systematically studied by using electric field modulation spectroscopy. For all PbS quantum dots samples, the electroabsorption spectra across the first and second exciton bands are similar in shape to the second derivative of the absorption spectra, indicating the enhancement of the electric dipole moment following the optical transition to these exciton bands. The analysis of the electroabsorption spectra shows that the dipole moments for both first and second exciton bands increase a little bit with increasing particle size. The quadratic field dependence is observed between the modulated absorption spectrum and the electric field of PbS quantum dots doped in a PMMA film.