Photoluminescence dynamics in solid formulations of colloidal PbSe quantum dots: Three-dimensional versus two-dimensional films

Time-resolved photoluminescence spectroscopy is used to compare decay dynamics of colloidal PbSe quantum dots as (i) dilute dispersions in hexanes, (ii) thick, dense, emulsive films, and (iii) sub-monolayer films on silicon surfaces. Accounting for the effect of each dielectric environment on exciton radiative decay rates, we deduce the non-radiative decay rate of excitons increases going from solution to thick films by approximate to 6 fold and to sub-monolayer films by approximate to 7-16 fold. This is attributed to surface passivation degradation due to a lack of mobile ligands when the particles are taken out of solution. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752737]