Composition engineered ternary copper chalcogenide alloyed counter electrodes for high-performance and stable quantum dot-sensitized solar cells

Abstract

The rational design and development of economical, high-performance, and stable counter electrodes (CE) are critical to bringing the quantum dot-sensitized solar cell (QDSSCs) from the laboratory to a practical application. In this respect, we used a two-step approach to fabricate ternary copper chalcogenide (Cu 2−x S y Se 1−y ) alloyed semiconductors onto fluorine-doped tin oxide (FTO). In the first step, the binary copper chalcogenides CuS nanostructures that are synthesized using the microwave-irradiation technique are screen-printed onto the FTO substrate and annealed in a nitrogen atmosphere to obtain Cu 2−x S CE. In the second step, ternary Cu 2−x S y Se 1−y alloyed electrocatalyst is obtained through a composition engineering approach in which the elemental Se was incorporated on the surface of as-synthesized Cu 2−x S nanostructures using the drop-casting method. Compared to the pristine Cu 2−x S CE, the as-synthesized Cu 2−x S y Se 1−y CE has exhibited tunable crystal structures, compositions, morphologies. The electrochemical analysis revealed that the optimized Cu 2−x S y Se 1−y CE has exhibited low charge transfer resistance (R ct ), and excellent reduction activity to S n 2− species of the polysulfide electrolyte. Accordingly, QDSSCs assembled with Cu 2−x S y Se 1−y CE have delivered conversion efficiencies of 8.02%, which are higher than those of pristine Cu 2−x S CE (7.24%). Noticeably, Cu 2−x S y Se 1−y CE has demonstrated outstanding electrochemical stability in polysulfide redox couple , exhibiting no substantial fluctuations in either the current density or shape of the curve even after 200 continuous cyclic voltammetry (CV) cycles. Moreover, the best cell devices constructed using Cu 2−x S y Se 1−y CE validated remarkable stability under open-air conditions, retaining <60% of the original performance after 120 h of illumination. Overall, the ease of synthesis, low cost, time efficiency, and excellent electrocatalytic characteristics of the Cu 2−x S y Se 1−y alloyed semiconductors film demonstrated in this work make it an encouraging applicant for use as a CE material in photovoltaic applications. The two-step synthesis procedure of the ternary copper chalcogenide counter electrode. • Ternary copper chalcogenide (Cu 2−x S y Se 1−y ) alloyed electrocatalyst developed. • Cu 2−x S y Se 1−y exhibited compositions dependent tuneable crystal structures and surface morphologies. • Cu 2−x S y Se 1−y served as an efficient and stable counter electrode in the QDSSCs.