N‐doped titania powders prepared by different nitrogen sources and their application in quasi‐solid state dye‐sensitized solar cells

Nitrogen‐doped TiO₂ nanocrystalline particles are synthesized by a microwave‐assisted hydrothermal growth method using different amines (Dipropylamine, Diethanolamine and Ammonium hydroxide) as nitrogen sources. Characterization of the nanoparticles was performed with X‐ray diffraction, UV–vis diffuse reflectance spectroscopy, Field Emission Scanning Electron Microscopy and X‐ray Photoelectron Spectroscopy. The prepared N‐doped TiO₂ nanoparticles exhibit pure anatase phase with average diameter of 9 nm and reduced optical energy gap compared to undoped TiO₂. Immobilization of N‐doped and pure TiO₂ nanoparticles on SnO₂:F conductive glass substrates was successfully performed by using doctor‐blade technique and paste of the aforementioned nanoparticles. A series of N‐doped TiO₂ photoelectrodes with varying N dopant source and concentrations were fabricated for quasi‐solid state dye‐sensitized solar cells. The N‐doped solar cells achieve an overall conversion efficiency ranging from 4.0 to 5.7% while undoped TiO₂ showed 3.6%. The basic difference to the electrical performance of the cells is focused to the enhancement in the current density of N‐doped TiO₂‐based cells which was from 11% to 58% compared with undoped TiO₂ cells. Current densities were directly proportional with nitrogen doping level in TiO₂ lattice which differs depending on the amine source nature such as basicity differences, hydrogen bonding abilities and steric inherences. Copyright © 2013 John Wiley & Sons, Ltd.