Dear Najla el Aallaoui thank you for your very interesting technical question. Unsubstituted phthalocyanine and the related metal phthalocyanines are known for their very low solubility in organic solvents and insolubility on water. For example, it is stated in the Wikipedia entry cited below that less than 1 milligram of unsubstiruted phthalocyanine is soluble in 1 liter (!) of benzene at 40 °V:
https://en.wikipedia.org/wiki/Phthalocyanine
The same is true for the metal complexes of unsubstituted phthalocyanine. That's certainly the reason why most research articles describe substituted phthalocyanines in order to increase the solubility.
For unsubstituted metal phthalocyanines please have a look at the following useful article entitled
Solubility Properties of Unsubstituted Metal Phthalocyanines in Different Types of Solvents
Article Solubility Properties of Unsubstituted Metal Phthalocyanines...
In general, unsubstituted (metal free or metalled) phthalocyanines are insoluble in water except for the ones having axially hydrophilic ligand on the metal (like Si, Ga, In, etc.).
And you can decide to choose the best organic solvent and maximum concentration by searching the literature and then comparing it with their extinction coefficient values.