Highly efficient dye-sensitized solar cells based on nitrogen-doped titania with excellent stability
2011
Guo, Wei | Wu, Liqiong | Chen, Zhuo | Boschloo, Gerrit | Hagfeldt, Anders | Ma, Tingli
A series of nitrogen-doped and undoped TiO₂ nanocrystals was prepared by several simple methods. Needle-like N-doped TiO₂ nanocrystals and nanoparticles were obtained from commercial TiO₂ powders. Several dye-sensitized solar cells (DSCs) were fabricated based on N-doped and undoped TiO₂ electrodes. The N-doped DSCs achieved a high conversion efficiency of 10.1% and 4.8% using an organic electrolyte and an ionic liquid electrolyte, respectively. Systemic investigations were carried out on the properties of N-doped and undoped TiO₂ powders, films, and DSCs. The electron transport time and electron lifetime were investigated by intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS). Moreover, the electron injection of N-doped DSCs was studied by surface photovoltage spectroscopy (SPS). The synergetic effect of higher dye uptake, faster electron transport and higher photovoltage contributes to a higher conversion efficiency of N-doped DSCs. The stability test also demonstrated that the photodegradation of the DSCs was not accelerated and the DSC system was stabilized by the introduction of nitrogen into the TiO₂ photoelectrode. These results indicate that the N-doped TiO₂ nanocrystals prepared by our approach from commercial TiO₂ are ideal semiconductor materials for DSCs.
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