Continuous and time-resolved photoluminescence study of lead sulfide nanocrystals, embedded in polymer film

Nanometer-sized particles of lead sulfide were grown under excess sulfur co nditions and embedded in polyacrylamide polymer films. The particles show a spherical shape with a cubic crystal structure. The absorption and photolu minescence excitation spectra show a substantial blue shift (up to 2 eV) wi th a decrease in the particle size, due to a strong quantum size effect. Th e photoluminescence (PL) spectra consist of an exciton and deeper imperfect ion emission bands. The emission decay curves of the various PL bands show multi-exponential behavior,with a decay time in the microsecond range. The latter may be associated with trapping and de-trapping process among the ex citon and imperfection states. (C) 1999 Elsevier Science B.V. All rights re served.