semiconductor materials, generally has absorption under sun light commonly employed as self cleaning materials. TiO2, due to low cost, high availability in earth crust and with good activity people will choose as the self cleaning material. but other semiconductors like ZnO, SnO2 and ZrO2 will also shows good photocatalytic activity.   

ZnO is promising semiconductor material that is cheaper than TiO2 and you can synthesis it easily.

By doping other metals into ZnO or synthesis of its composites by graphene or other metal oxides with lower enery band gap you  can improve its photocatalytic activity significantly.

This strategy is also used to enable ZnO  to have photocatalytic activity under visible light.

You can find useful information in the article on my page.

Regards,

Habib