Iridium–palladium binary alloy as a counter electrode in dye-sensitized solar cells

Abstract

This study is concerned with the iridium–palladium (Ir–Pd) binary alloy as a counter electrode (CE) for DSSC. The CE was prepared using the liquid phase deposition (LPD) technique. The influence of the concentration of hydrogen hexachloroiridate(IV) hydrate (H₂Cl₆Ir·H₂O) on the properties and the performance of the device was investigated. The source of iridium was H₂Cl₆Ir·H₂O. XRD analysis confirmed that the dominant phase of Ir–Pd existed in the sample. The grain size of Ir–Pd increased with the increase in the concentration of H₂Cl₆Ir·H₂O until an optimum concentration of 0.7 mM was reached. The % wt of Ir was found to increase with the concentration of H₂Cl₆Ir·H₂O. The device utilizing Ir–Pd CE with 0.7 mM H₂Cl₆Ir·H₂O demonstrated the highest power conversion efficiency (PCE) of 5.84%, beating that of the device with Pt CE having a PCE of 5.04%. This is because the device possesses the lowest charge transfer resistance (R_ct), highest recombination resistance (R_cr), and longest carrier lifetime (τ), and the device possesses the highest reduction current (J_pc) and incident-photon conversion efficiency (IPCE). The PCE was significantly affected by Ir content in the binary alloy of Ir–Pd. According to the PCE result, Ir–Pd CE was found as a suitable substitution for Pt as CE for the device.