Effect of Annealing Temperature on Tantalum-Doped TiO2 as Electron Transport Layer in Perovskite Solar Cells

Plasma-enhanced atomic layer deposition is used to fabricate compact tantalum (Ta)-doped titanium oxide (TiO
₂
) thin films as electron transport layers (ETLs) and hole blocking layers for perovskite solar cells (PSCs). The effects of Ta-doped TiO
₂
with different annealing temperatures on film structure and electronic properties are researched. The experimental results exhibit that the substitutional Ta-doping into TiO
₂
(Ta content of ~1.5%) increases the stability of crystal structure and passivates the material defects, thereby improving the film quality. The annealed Ta-doped TiO
₂
films have a resistivity of approximately 6.5
$\boldsymbol {\Omega } \cdot $
cm which is three orders of magnitude lower than 3.4
$\times 10^{{3}}\,\, \boldsymbol {\Omega } \cdot $
cm of intrinsic TiO
₂
. Finally, the annealing process eliminates the defects, and therefore, improves electron transport for PSCs, leading to a clearly enhanced fill factor (FF) of 0.77 and conversion efficiency of 19.62% when compared to that of undoped TiO
₂
ETL devices.