Abstract

Herein, a further investigation about the effect of imidazolium cations on electron transport and recombination behavior in dye-sensitized solar cells (DSCs) is developed in this paper. MPII is synthesized and used as iodide sources and TBAI is applied as a reference. The adsorption amount of MPI⁺ and TBA⁺ onto TiO₂, band edge shifts, trap states distribution, electron recombination/transport processes and ion transport within the electrolyte are detected. It is found that the multilayered adsorption of MPI⁺ can induce much less photoinduced electrons and has competition with the effect of lithium ion. As the TBA⁺ is weak adsorption species, in comparison to MPI⁺, its coexistence with lithium ion contributes a more band edge positive shift. Furthermore, the reduced effect of Li⁺ in MPII cell induces a lower short-circuit current density (J_sc) and a higher open-circuit voltage (V_oc). Electrochemical impedance spectroscopy indicates that MPI⁺ can improve the ions transport process in electrolyte, but TBA⁺ induces large power dissipation due to its large ion radius for contrast. Overall, MPII cell gives a higher efficiency ascribe to the effective improvement of fill factor.

© 2013 Optical Society of America