In Situ Gravimetric Probing of Copper Sulfide Formation on the Counter Electrode for Quantum Dot Sensitized Solar Cells

摘要

Coppersulfide is a classical counter electrode (CE) catalyticmaterial for the high catalytic activity of polysulfide in quantumdot-sensitized solar cells (QDSSCs). Actually, copper sulfide is acomplicated compound. Different preparation methods will lead to thedifference in the morphology and structure of copper sulfide, whichhas a profound impact on its catalytic activity. However, the formationmechanism and electrochemical properties of copper sulfide are rarelyreported in the field of QDSSCs. Herein, we report an approach toobtain a high-stability counter electrode material by the electrochemicalsynthesis in sodium sulfide solution. The in situ electrochemicalquartz crystal microbalance (EQCM) method was also employed to revealthe detailed transformation mechanism of copper vulcanized into coppersulfide during cyclic voltammetry in sodium sulfide solution. Accordingto the calculation results of mpe theory, the formation of coppersulfide is accompanied by side reactions such as the conversion ofpolysulfide ions and water oxidation. Copper sulfide was proven tobe a copper-rich phase by X-ray photoelectron spectroscopy (XPS) andother characterization methods. The photoconversion and stabilityof QDSSCs were studied using CdSe QD as the sensitizing material.The results show that the performance of copper sulfide prepared bythis working method is better than the CE prepared by chemical bathdeposition (CBD), and the replicability of photoelectric conversionefficiency (PCE) is better than CBD-CE. This work has theoreticalsignificance to reveal the complex formation mechanism, electrochemicalprocess mechanism, and working mechanism of copper sulfide in QDSSCs.

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