Performance enhancement of dye-sensitized solar cells with KMnO₄-modified photoelectrodes

In order to reduce the interfacial charge recombination between photoinjected electrons and triiodide ions in the electrolyte, a TiO₂ surface was modified with potassium permanganate (PM). The PM-modified TiO₂ electrodes were prepared by soaking the TiO₂ films in an aqueous PM solution, and the resulting electrodes were applied to the photoanodes of dye-sensitized solar cells (DSSCs). The power conversion efficiency of a DSSC with a PM-modified TiO₂ electrode was improved from that of the reference device without any modification, due to an enhancement in the open-circuit voltage (V_oc), short-circuit photocurrent (J_sc), and fill factor (FF). By monitoring open-circuit voltage decay, electrochemical impedance, dark current, and UV-visible absorbance, it was revealed that the incorporation of the permanganate group on the TiO₂ surface induced a longer electron lifetime because of the suppression of charge recombination between photoinjected electrons and I₃ ^- ions, leading to the increase in V_oc, J_sc, and FF.