Recent advances in counter electrodes of quantum dot-sensitized solar cells

Over the past few decades, various types of solar cells provided alternative ways for solar energy conversion. Among them, quantum dot-sensitized solar cells (QDSCs) have gained significant interest due to the advantages of quantum dots (QDs) including easy fabrication, multiple exciton generation, band-gap energy controllability and high absorption coefficient. A QDSC consists of a metal oxide photoanode, QDs, electrolyte and a counter electrode (CE). In comparison with the photoanode and QDs, the CE has not been paid much attention. As an essential part of QDSCs, the CE plays an important role in the charge transport and collection of the device. Here, the recent progress in the development of CEs is reviewed, and the key issues for the materials, structures and performance evaluation of CEs are also addressed.