Facile synthesis of ordered Nb2O5 coated TiO2 nanorod arrays for efficient perovskite solar cells

Reducing defect density and hindering charge recombination in perovskite film and at perovskite/semiconductor interface are crucial to perovskite solar cells (PSCs) performance. In this paper, hydrothermally prepared TiO 2 nanorod arrays (TNRAs) were coated with Nb 2 O 5 layer using a spin-coating method, and the modified TNRAs were used as scaffold for the deposition of perovskite films and corresponding PSCs in air environment. The effect of NbCl 5 concentration on the micro structure and photovoltaic properties of the formed perovskite films were investigated, and the enhancement mechanism was also elucidated. A champion efficiency of 16.50% (enhanced of 9.49% compared with the pristine one) was achieved when the concentration of NbCl 5 solution was 0.005 M. Such an enhanced performance of PSC might be mainly ascribed to two reasons: one was the improved perovskite film qualities including the enlarged average grain size, higher crystallinity and reduced defect density; the other was the formed energy barrier (Nb 2 O 5 ) between perovskite layer and TNRAs interface that hindered the charge recombination.