I have been working with Perovskite Solar Cells, and there are many architectures possible. FTO/SnO2 an ITO/TiO2 are actually used too, check these papers:
Enhanced photovoltaic properties in dye sensitized solar cells by surface treatment of SnO2 photoanodes
Perovskite Solar Cells with Low-Cost TiO2 Mesoporous Photoanodes Prepared by Rapid Low-Temperature (70 °C) Plasma Processing
I can't tell which of these architecture is the most used, is looks like many people achieved different ways to obtain very high quality results. I would suggest you to find out what method you can follow. Please, if you have any issue with this, let me know.