In an embodiment of the invention, the perovskite precursor solution is also an ink solution, as it can be deposited by printing techniques.

In a preferred embodiment of the invention, the perovskite precursor solution comprises all components required to form said perovskite. Preferably, said precursor solution or ink, when deposited, results in the formation of perovskite crystals forming said perovskite.

The person skilled in the art would expect, from the fact that said precursor solution comprises all components required to form said perovskite, that the precursor solution is not stable, because of the formation of crystals and/or precipitates during storage of the solution. Surprisingly, the precursor solution of the invention is preferably sufficiently stable to allow for printing.

In a preferred embodiment, the perovskite precursor solution comprises a compound or component that is suitable to inhibit, slow down, reduce and/or prevent one or more selected from: nucleation rate, crystal growth and precipitation of perovskite, perovskite crystals and/or a perovskite intermediate phase. Said compound may be referred to as “precipitation retarding compound” or more shortly “retarding compound”. This compound may be any compound suitable to prevent or slow down precipitation of perovskite or perovskite intermediates in the precursor solution, while enabling and/or not preventing such precipitation upon deposition of the precursor solution. In an embodiment, the compound may allow crystallization and/or precipitation upon an additional process step, for example following heating. In an embodiment, the method of the invention comprises heating the deposited perovskite precursor solution, so as to as remove solvent and/or initiate and/or accelerate one or more selected from precipitation and perovskite crystal growth.