Dye-sensitized solar cells (DSSCs) have attracted widespread attention in recent years as potential cost-effective alternatives to silicon-based and thin-film solar cells. Within typical DSSCs, the counter electrode (CE) is vital to collect electrons from the external circuit and catalyze the I3- reduction in the electrolyte. Careful design of the CEs can improve the catalytic activity and chemical stability associated with the liquid redox electrolyte used in most cells. In this Progress Report, advances made by our groups in the development of CEs for DSSCs are reviewed, highlighting important contributions that promise low-cost, efficient, and robust DSSC systems. Specifically, we focus on the design of novel Pt-free CE catalytic materials, including design ideas, fabrication approaches, characterization techniques, first-principle density functional theory (DFT) calculations, ab-initio Car-Parrinello molecular dynamics (CPMD) simulations, and stability evaluations, that serve as practical alternatives to conventional noble metal Pt electrodes. We stress the merits and demerits of well-designed Pt-free CEs, such as carbon materials, conductive polymers, transition metal compounds (TMCs) and their corresponding hybrids. Also, the prospects and challenges of alternative Pt catalysts for their applications in new-type DSSCs and other catalytic fields are discussed.

New-generation integrated devices based on dye-sensitized and perovskite solar cells for energy harvesting and storage are significantly important for self-powering systems and portable/wearable electronics.

We report a confined proton transportation in the CeO 2 /CeO 2−δ core−shell structure to build up proton shuttles, leading to a super proton conductivity of 0.16 S cm −1 for the electrolyte and advanced fuel cell performance, 697 mW cm −2 at 520 °C. The semiconductor nature of the CeO 2 (i-type) core and the CeO 2−δ (n-type) shell reveals a unique proton transport mechanism based on the charged layers formed at the interface of the CeO 2−δ /CeO 2 heterostructure. Two key factors of this structure confine proton transport to the particle surface. The first is the high concentration of oxygen vacancies in the surface layer, which benefits proton conduction. The second is a depletion region created by the core−shell interface that allows proton migration only on the surface layer rather than into the bulk CeO 2 . The constrained surface region of the CeO 2−δ builds up continuous proton shuttles. This work presents a new methodology and understanding for proton transport in general oxides and a new generation proton ceramic fuel cells.