Cadmium and ytterbium Co-doped TiO2 nanorod arrays perovskite solar cells: enhancement of open circuit voltage and short circuit current density

Abstract

TiO2 nanorod arrays of crystalline Cd, Y-co-doped rutile were synthesized and successfully assembled in perovskite solar cells (PSCs) as the photoanode. In this work, CH3NH3PbI3−xClx was used as the light absorber and spiro-OMeTAD as hole transport material (HTM). The synthesized TiO2 nanorod arrays were investigated by field emission-scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRD) and UV–Vis diffused reflectance. FE-SEM images indicate that the co-doped TiO2 nanorod arrays were slightly sparser and shorter in length than that of un-doped ones. XRD pattern demonstrates that the as-prepared TiO2 nanorod arrays were rutile phase. The UV–Vis spectrum proves that the co-doped samples possess higher light scattering intensity than the un-doped samples, which may contribute to improve the short current density of PSCs. And the band gap of the TiO2 nanorod shows a positive shift when doped with cadmium and ytterbium. Furthermore, a negative shift in the flat-band potential (Vfb) was also observed. Finally, the device based on co-doped TiO2 nanorod arrays has improved open circuit voltage (Voc) and short circuit current density (Jsc). A higher power conversion efficiency (η) of 9.06% was obtained for the co-doped device while 8.12% for the un-doped TiO2 nanorod arrays. This paper opens a door to multi-element co-doped 1-D nanostructured materials for the improving the open circuit voltage and short circuit current density of perovskite solar cells.