Sustainable coconut shell charcoal counter electrodes for efficiency enhancement in CdS quantum dot solar cells

The use of activated coconut shell charcoal (ACSC) was explored as a cost-effective and viable alternative to platinum (Pt) counter electrodes (CE) in CdS quantum dot–sensitized solar cells (QDSSCs). The photovoltaic performances of QDSSCs with newly fabricated ACSC CEs by spraying method and Pt CEs were evaluated using current density–voltage measurements under 100 mWcm−2 light illumination. While the QDSSC with a Pt CE showed an efficiency of 1.26%, the QDSSC with an ACSC CE, with an optimal thickness of 25 μm, corresponding to a spray time of 60 s, showed an efficiency of 2.93%, demonstrating a more than two-fold increase in the efficiency. The physicochemical parameters of ACSC CEs were analyzed using FTIR, Raman, X-ray diffraction, cyclic voltammetry (CV), and Tafel characterization. CV, Tafel, and electrochemical impedance (EIS) analysis confirmed the superior electrocatalytic activity of the ACSC CE compared to the Pt CE for QDSSCs. The efficiency enhancement can be attributed to the increased photocurrent density due to the superior electrocatalytic activity of ACSC, which promotes efficient polysulfide reduction at the electrolyte/counter electrode interface. The porous nature of ACSC provides an increased specific surface area, facilitating redox reactions and improving the interaction between the electrolyte and the counter electrode. Additionally, the enhanced charge transfer capabilities of the ACSC-based counter electrode contribute to efficient electron transport and reduced recombination losses. These properties collectively optimize the cell’s performance by ensuring effective energy conversion. Consequently, ACSC is emerging as a promising novel material for counter electrodes in QDSSCs.