Random nanowires of nickel doped TiO2 with high surface area and electron mobility for high efficiency dye-sensitized solar cells

Mesoporous TiO2 with a large specific surface area (similar to 150 m(2) g(-1)) is the most successful material in dye-sensitized solar cells so far; however, its inferior charge mobility is a major efficiency limiter. This paper demonstrates that random nanowires of Ni-doped TiO2 (Ni:TiO2) have a dramatic influence on the particulate and charge transport properties. Nanowires (dia similar to 60 nm) of Ni:TiO2 with a specific surface area of similar to 80 m(2) g(-1) were developed by an electrospinning technique. The band gap of the Ni:TiO2 shifted to the visible region upon doping of 5 at% Ni atoms. The Mott-Schottky analysis shows that the flat band potential of Ni:TiO2 shifts to a more negative value than the undoped samples. The electrochemical impedance spectroscopic measurements showed that the Ni:TiO2 offer lower charge transport resistance, higher charge recombination resistance, and enhanced electron lifetime compared to the undoped samples. The dye-sensitized solar cells fabricated using the Ni:TiO2 nanowires showed an enhanced photoconversion efficiency and short-circuit current density compared to the undoped analogue. The transient photocurrent measurements showed that the Ni:TiO2 has improved charge mobility compared with TiO2 and is several orders of magnitude higher compared to the P25 particles.