In solution, the QDs will have similar electronic environments due to the fact that they are suspended and likely interacting with all the other particles in a similar way. When you  deposit the QDs onto your pillar structure, the elongation of the PL signal is likely from the inhomogenous electronic environment that is now forced onto the QDs. Things like aggregation or deposition effects will now be seen when they weren't in solution. The fact that the tail is growing out to the low energy, high wavelength side of the signal tells me that you are inducing more trap states in the QDs than in solution which would be a feature of the deposition process. 

Dear Eric Amerling  thank you very much.