Recent Progress in Non‐Platinum Counter Electrode Materials for Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) have gained increasing attention with regard to photovoltaic devices, because of their low cost and simple fabrication methods; they are mostly investigated in indoor light‐harvesting and portable applications. The focus has been on three main parameters of photovoltaic devices, that is, lifetime, and cost effectiveness. A DSSC consists of four prominent components including a photoanode, a photosensitizer, a redox electrolyte, and a counter electrode. The counter electrode is a crucial component, in which triiodide is reduced to iodide by electrons flowing through the external circuit. An effective approach to improve the performance of a counter electrode is to enhance the power conversion efficiency and to reduce the cost of the device. Platinum‐coated conducting glass electrodes give the best performance, but their high cost and the scarcity of platinum restricts large‐scale application in DSSCs. This has prompted researchers to develop low‐costing platinum‐free electrodes for DSSCs. In this review, we focus mainly on counter electrode materials for the electrocatalytic redox reaction for the I−/${{\rm{I}}_{\rm{3}}^ - }$ electrolyte, and apart from this, other counter electrode materials for iodine‐free redox electrolytes are discussed. Different counter electrode materials are highlighted in different categories such as carbon materials, conducting polymers, oxide and sulfide materials, transition‐metal nitrides and carbides, and composite materials. The stability of counter electrodes in DSSCs is also presented. Getting a little sun: Recent progress in the replacement of the platinum counter electrode with other cheaper materials for dye‐sensitized solar cells (DSSCs) is presented. Platinum‐free counter electrode materials are categorized into carbon materials, conducting polymers, inorganic metal oxides and metal sulfides, transition‐metal nitrides and carbides, and composite materials, and the advantages of these platinum‐free catalysts for DSSCs are highlighted.