Room-temperature amplified spontaneous emission at 1300 nm in solution-processed PbS quantum-dot films

We report room-temperature amplified spontaneous emission and spectral narrowing at infrared wavelengths in solution-processed films made up of PbS quantum-dot nanocrystals. The results are relevant to optical amplification and lasing integrated upon a variety of substrates. The active optical medium operates at room temperature without any additional matrix material, providing an optical gain of 260 cm(-1) and a pump threshold of 1 mJ/cm(-2). Nanocrystals synthesized in an aqueous solution and stabilized by use of short ligands result in high quantum-dot volume fractions in solid films and in a redshift emission relative to absorption.

Time-resolved luminescence in conducting polymer/antidot nanocomposites

We report modification of the structure and properties of conjugated polymers through controlled embedding wide-gap nanocrystals (antidots) within the polymer matrix. Investigations were carried out by means of stationary and time-resolved photoluminescence. Antidots strongly modify the luminescence spectrum of poly(p-phenylene vinylene) but have almost no influence on the spectrum of poly(2-(6-cyano-6'-methylheptyloxy)-1, 4-phenylene. We explain this observation with respect to the different chain structure and electron density distribution in these two materials. The temporal evolution of luminescence spectra in polymer/antidot composites contains a series of characteristic times. The shortest of these (0.35-0.6 ns) are independent of antidot material and characterize processes in the polymer matrix. Larger times considerably exceeding 1 ns are composition-sensitive and attributable to carrier capture by nanocrystals. The qualitative character of the modification of luminescence spectra associated with the inclusion of antidots depends strongly on the characteristics of the polymer matrices and more weakly on the antidot material. This suggests that the predominant effect of the nanocrystals relates to the modification of the matrix near the polymer-inorganic interface.