Influence of PbS Quantum Dots-Doped TiO2 Nanotubes in TiO2 Film as an Electron Transport Layer for Enhanced Perovskite Solar Cell Performance

Lead sulfide quantum dots-doped titanium dioxide nanotubes (PbS QDs-doped TNTs) were successfully prepared by the hydrothermal and impregnation methods. A thin layer of titanium dioxide (TiO
₂
) comprising of PbS QDs-doped TNTs was applied as an electron transport layer (ETL) in order to improve the planar perovskite solar cell efficiency. The role of incorporating a high surface area of one-dimensional nanotube structure of TiO
₂
in the conventional TiO
₂
layer provided a special unidirectional charge transport and a high charge collection. Moreover, doping PbS QDs onto the surface of TNTs modified the electronic and optical properties of the ETL by downshifting the conduction band of TiO
₂
from -4.22 to -4.58 eV, therefore promoting the driving force of an electron injection to the transparent conductive electrode. By varying the concentration of PbS QDs-doped TNTs dispersed in 2-butanol from 0.1 to 0.9 mg/mL, a concentration of 0.3 mg/mL PbS QDs-doped TNTs was the optimum concentration to be mixed with TiO
₂
solution for the ETL deposition. The best perovskite solar cell performance with the optimum loading of PbS QDs-doped TNTs provided 14.95% power conversion efficiency, which was increased from 12.82% obtained from the cell with pristine TiO
₂
film as ETL.