Surface modification of platinum counter electrode by amino quinonoid zwitterion to improve the performance of dye-sensitized solar cells

Exploring ways to modify electrode surfaces is key to protecting the electrode while improving the performance of dye-sensitized solar cells (DSC). This study investigated the effect of surface modification with the amino quinonoid 4-methylamino-6-methylamino-3-oxocyclohexa-1,4-dien-1-olate (AQZ) of Pt counter electrode, the most effective and widely-used DSC cathode, on the photovoltaic performance of DSC. The Pt surface on conductive glass substrates was treated with AQZ solutions at various concentrations (0.2–2.0 mg.mL⁻¹) and intervals (0.5–60 min) and characterized by X-ray photoelectron spectroscopy and field emission scanning electron microscopy to examine the chemical environment and morphology, respectively. The I⁻/I₃⁻ reactions with bare and AQZ-treated electrodes were compared using cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarized measurement. Current–voltage analysis showed that Pt cathode treated with 2 mg.mL⁻¹ AQZ for less than 5 min or in diluted AQZ solution (0.2 mg.mL⁻¹) for as long as 60 min could improve the photovoltaic performance of DSC as much as 22%, mostly due to the enhancement of the short circuit current (about 3–4 mA.cm⁻²). The promising results of electrode surface modification with AQZ developed in this report allow future development of simple methods to further improve photovoltaic devices as well as for a wide range of applications in metal surface protection.