Enhanced performance of perovskite solar cells based on vertical TiO2 nanotube arrays with full filling of CH3NH3PbI3

Abstract

Due to a wide range of intriguing properties, such as efficient one-dimensional (1D) electron pathways and extraordinarily large surface areas, titanium dioxide (TiO2) nanotube arrays are considered as the promising electron transport material for high-performance perovskite solar cells (PVSCs). However, it is still a great challenge to directly synthesize the TiO2 nanotube arrays with well-controlled geometries (e.g., diameter and height, etc.) on the surface of fluorine-doped tin oxide (FTO). Here, vertically standing TiO2 nanotube arrays with desirable heights and diameters are directly synthesized on the FTO surface by employing the aqueous TiO2 sol-gel method on tubular photoresist templates. The tube height can be precisely tailored within a range of 350–900 nm for the effective loading of perovskite precursor solution. Importantly, it is demonstrated that TiO2 nanotube arrays with the optimized tube diameter and length can facilitate the infiltration of perovskite precursor solution, and thus ensuring the formation of a dense, smooth and large grain-sized perovskite film. Moreover, the contact between the perovskite and TiO2 nanotube arrays are enhanced simultaneously. Benefiting from the high-quality perovskite film, good interfacial contact at the perovskite/TiO2 tube interface, enhanced light trapping as well as rapid electron collection and transport induced by one-dimensional TiO2 nanotubes, the fabricated PVSCs exhibit an impressive power conversion efficiency (PCE) of up to 14.13%. Our work does not only demonstrate the promising potential of vertical TiO2 nanotube arrays for PVSCs, but also provides valuable insights into the design and utilization of TiO2 nanotubes for practical applications.