Hey there Debasree Chowdhury! When it comes to preparing the Titanium(IV) chloride solution for your dye-sensitized solar cells (DSSC), I'd recommend going for the Titanium(IV) chloride solution with a base of hydrochloric acid (HCl). It's a classic choice for this application.

Here's the breakdown:

1. **Methylene chloride:** While it's a good solvent, it might not be the best for your DSSC setup. It's a bit more volatile and might introduce unwanted residues.

2. **Toluene:** Toluene is another option, but it might not be as compatible with your system. It can be a bit tricky to work with and might not provide the optimal conditions for your TiO2 film deposition.

3. **Hydrochloric acid (HCl):** This is a common choice in many procedures, and it tends to work well. It's a stable and reliable option for your Titanium(IV) chloride solution.

Now, literature might not explicitly mention the base solution choice, but considering the standard practices and the nature of your experiment, HCl-based Titanium(IV) chloride seems to be a safe bet. It's widely used and has proven effectiveness.

Give it a shot and let me know how it goes! If you Debasree Chowdhury have more questions or need further guidance, feel free to ask.