PEDOT-based counter electrodes for dye-sensitized solar cells: rigid, flexible and indoor light applications

Dye-sensitized solar cells (DSSCs) are promising technology owing to their unique properties such as high transparency, good color tunability, and easy large-area fabrication, which make them attractive candidates for emerging photovoltaic applications. However, conventional DSSCs require high-temperature processing for working and counter electrodes (WEs and CEs, respectively), limiting their diverse applications. Low temperature processing for highly catalytic CEs, particularly using poly(3,4-ethylenedioxythiophene) (PEDOT) as a conducting and catalytic replacement for platinum, shows potential for increased efficiency under various light conditions. Despite the high catalytic activity of PEDOT, its limited solubility and processing technologies (e.g., electrochemical deposition and spin-coating) have necessitated the interest in composites of PEDOT either with poly(styrene sulfonate), metal compounds, or in combination with carbon materials, aiming to overcome these limitations. With the combined properties of high conductivity, catalytic activity, porosity, and low temperature processability, these CEs based on PEDOT have higher scientific and industrial prospects. Moreover, the highly transparent PEDOT-based CEs can also be used for bifacial application in DSSCs. To continuously draw interest to further research on these materials, this review provided an overview of PEDOT-based CEs for rigid, flexible, and indoor applications of DSSCs. Additionally, we discuss the changes in electronic, chemical, and stability properties associated with the formation of each type of composite material. The challenges and prospects of PEDOT-based materials are further highlighted, which pave the way for performance improvements in the future, as well as identifying other potential applications in the semiconductor industry.