Amorphous TiO2 film with fiber like structure: An ideal candidate for ETL of perovskite solar cells

• E T L A m o r p h o u s T i O 2 was prepared by DCP-MS at room temperature. • Lots fiber like structures run through the E T L A m o r p h o u s T i O 2 directly. • Fiber like structures in E T L A m o r p h o u s T i O 2 improves electron transfer efficiency. • PCE of PSCs improves from 4.7% of E T L A n a t a s e T i O 2 to 11.5% of E T L A m o r p h o u s T i O 2 . Organic-inorganic hybrid metal halide perovskite solar cells (PSCs) with planar heterojunction structures were fabricated. The amorphous and anatase TiO 2 electron transfer layer (ETL) was deposited by the direct current pulsed magnetron sputtering technology. With the ordinary CH 3 NH 3 PbI 3 , PSCs with amorphous and anatase TiO 2 ETL showed the average power conversion efficiency in (11.5±0.7)% and (4.7±1.5)%, respectively. Combining with XRD and TEM results, the fiber like structure in amorphous TiO 2 ETL resulted in the increase of average power conversion efficiency of PSCs. Finally, amorphous TiO 2 with fiber like structure is an ideal ETL for PSCs, which is prepared by sputtering.