Importance of ligands on TiO2 nanocrystals for perovskite solar cells
Zhao Yao, Zhao Yi-Cheng, Zhou Wen-Ke, Fu Rui, Li Qi, Yu Da-Peng, Zhao Qing †
       

(color online) UPS measurement of TiO2 and TiAc2-modified TiO2 film.