Dear Raad S.Sabry , 

Do you have any idea on solvents used to make sol for spin coating

Hii, 

The solvent you can prefer is Ethanol.

We used titanium(IV) isopropoxide (Ti-(OiPr)4) in isopropanol with room temperature processing to achieve a PCE of 16.3% with MAPbI3 perovskite solar cell in the attached publication. Commonly, titanium diisopropoxide bis(acetylacetonate) in butanol is used but it requires high temperature (450°C) annealing.

Article Room Temperature Processing of TiOx Electron Transporting La...

Dear Anil,

I think you need to employ low temperature TiO2 films processing in term of using PET/flexible substrate. 

Here I attached good study about low temperature TiO2 from Prof Sargent's group with PCE above 20%.

Good luck. 

Article Efficient and stable solution-processed planar perovskite so...

you can try with iso propyl alcohol also

You cannot use a precursor assisted (titanium isopropoxide) or sol-gel (commercial paste with binders) method to uniformly deposit TiO2 which requires high temperature firing, then this would also burn your plastic substrate.

So disperse commercial TiO2 particles in ethanol ( evaporates @ ~ 80 deg C).

Concentration should be varied according to the requirement. Then use any thin film technique depending on the required thickness.

You can use screen printing methods

You can use screen printing methods.

You can use screen printing methods.

You can use screen printing methods