Design of robust carbon dot-wrapped PtCu as an efficient counter electrode in liquid junction photovoltaic devices

This study explores a green and straightforward strategy to modify and protect counter electrodes (CEs) in dye-sensitized solar cells (DSCs). All synthesis steps, including plasma reduction, microwave treatment, and dip-coating, were designed to minimize environmental impact. PtCu-based CEs modified with carbon dots (CDs) exhibited changes in electrocatalytic performance, as suggested by CV, EIS, and Tafel analyses. The effect of CDs loading, adjusted via immersion time, on power conversion efficiency (PCE) was also evaluated. Among the DSCs examined, the highest PCE (6.21 %) was recorded for the device employing a PtCu/CDs counter electrode immersed for 40 min, although the improvement was relatively modest compared to the cell using a PtCu CE (5.83 %). The most notable finding was revealed by impedance measurements on symmetric cells before and after one week of aging. While the charge transfer resistance (R_ct) of the cell using a PtCu CE increased from 39.83 to 789.4 Ω, those incorporating CDs exhibited stable or reduced R_ct values. These findings suggest a potential stabilizing role of CDs at the electrode–electrolyte interface. Nonetheless, further long-term stability tests on complete DSC devices are needed to confirm this effect. This work highlights the potential of CDs for environmentally responsible CE modification in DSCs.