Unfortunately, we do not have too much data about the solution stability.

In our case, we uses this immediately after its preparation.

My colleague Shahzada Ahmad says:

"

We exactly don’t know what happen to charge dynamics, but we use fresh samples of Spiro.

I believe with time it is over oxidation on liquid state.

I will suggest reading this wonderful article.

http://pubs.rsc.org/en/content/articlelanding/2014/cp/c3cp53834f#!divAbstract

If the Spiro-OMeTAD solution is stored in dark, there is nothing to be worried about. Spiro-OMeTAD suffers from a photo-oxidation process which is accelerated by the additives; note that even with additives light is necessary to catalyze de reaction.

I suggest you to read the following article by clicking the the link: https://www.researchgate.net/publication/301207827_Light-induced_effects_on_Spiro-OMeTAD_films_and_hybrid_lead_halide_perovskite_solar_cells

Thank you very much for your help!