Effects of PbS Quantum Dot doped TiO2 Nanotubes as Electron Transporting Layer on the Efficiency of Perovskite Solar Cells

Abstract

TiO2 nanotubes (TNTs) are used as an excellent electron transporting layer for high efficiency perovskite solar cells. In this work, TNTs were synthesized via hydrothermal process from different particle sizes of TiO2 nanoparticle precursors as follows: 5 nm, 25 nm, and 50 nm. The highest surface area of 312.39 m2/g of TNTs was obtained from TiO2 precursor with particle size of 25 nm and was used to dope with lead sulfide quantum dots (PbS QDs). Due to a large band gap and poor conductivity of TNTs which limits the efficiency to transport electrons in the perovskite solar cell, PbS QDs doped TNTs were prepared to modify the valence and conduction energy bands of TNTs which can enhance the power conversion efficiency of perovskite solar cells. A slight decrease in the energy band gap of PbS QDs doped TNTs to about 2.97 eV was obtained. Both pure TNTs and PbS QDs doped TNTs were deposited onto the perovskite layer as the ETL with various concentrations of TNTs and PbS QDs doped TNTs in TiOX. The best power conversion efficiency (PCE) of the perovskite device prepared from the concentrations of 0.3 mg/ml of PbS QDs doped TNTs in TiOX is 14.95%, which is about 15% higher than that of perovskite solar cell with pure TNTs in TiOX. As a consequence, ETL in nanotube structure has proved to be an efficient structure for transporting electrons in the perovskite solar cell. Moreover, high surface area TNTs offer the enhanced interfacial area for doping with PbS QDs, which ultimately improved the property of ETL and resulted in the enhanced PCE as a consequence of appropriate band gap.