Interfacial engineering of mp-TiO 2 /CH 3 NH 3 PbI 3 with Al 2 O 3 : Effect of different phases of alumina on performance and stability of perovskite solar cells

In this paper, α , γ and amorphous Al 2 O 3 were deposited on mesoporous TiO 2 by spin coating technique. Among the phases of alumina used for coating the TiO 2 layer, photo anode electrode prepared by γ -Al 2 O 3 showed better photovoltaic properties than those covered by α and amorph-Al 2 O 3 . The perovskite solar cells which constructed by surface passivated TiO 2 films showed worse performance and stability than the unpassivated devices. Also, using the amorphous phase of alumina as substrate of perovskite in the structure of perovskite solar cells leads to lower solar cell stability (remain about 49% of efficiency after 70 days) compared to using α and γ -Al 2 O 3 as substrate of perovskite (remain about 68% of efficiency after 70 days). Our findings provide vital understanding to improve the performance and stability of TiO 2 - and Al 2 O 3 -based perovskite solar cells. Graphical abstract