Three classes (carbides, nitrides and oxides) of nanoscaled early-transition-metal catalysts have been proposed to replace the expensive Pt catalyst as counter electrodes (CEs) in dye-sensitized solar cells (DSCs). Of these catalysts, Cr(3)C(2), CrN, VC(N), VN, TiC, TiC(N), TiN, and V(2)O(3) all showed excellent catalytic activity for the reduction of I(3)(-) to I(-) in the electrolyte. Further, VC embedded in mesoporous carbon (VC-MC) was prepared through in situ synthesis. The I(3)(-)/I(-) DSC based on the VC-MC CE reached a high power conversion efficiency (PCE) of 7.63%, comparable to the photovoltaic performance of the DSC using a Pt CE (7.50%). In addition, the carbide catalysts demonstrated catalytic activity higher than that of Pt for the regeneration of a new organic redox couple of T(2)/T(-). The T(2)/T(-) DSCs using TiC and VC-MC CEs showed PCEs of 4.96 and 5.15%, much higher than that of the DSC using a Pt CE (3.66%). This work expands the list of potential CE catalysts, which can help reduce the cost of DSCs and thereby encourage their fundamental research and commercial application.

We report photovoltaic performances of all-solid state Sn/Pb halide-based perovskite solar cells. The cell has the following composition: F-doped SnO2 layered glass/compact titania layer/porous titania layer/CH3NH3SnxPb(1-x)I3/regioregular poly(3-hexylthiophene-2,5-diyl). Sn halide perovskite itself did not show photovoltaic properties. Photovoltaic properties were observed when PbI2 was added in SnI2. The best performance was obtained by using CH3NH3Sn0.5Pb0.5I3 perovskite. 4.18% efficiency with open circuit voltage 0.42 V, fill factor 0.50, and short circuit current 20.04 mA/cm(2) are reported. The edge of the incident photon to current efficiency curve reached 1060 nm, which was 260 nm red-shifted compared with that of CH3NH3PbI3 perovskite solar cells.

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.

Sunny prospects for renewable energy: Molybdenum and tungsten carbides embedded in ordered nanomesoporous carbon materials as well as Mo2C and WC are proposed as alternatives to the expensive platinum counter electrode (Pt CE). The preparation of the CEs was optimized, and the dye‐sensitized solar cells (DSCs; see picture) equipped with these CEs show a higher energy conversion efficiency than those devices with a Pt CE.

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Tungsten dioxide (WO(2)) nanorods were synthesized, which showed excellent catalytic activity for the reduction of triiodide to iodide. The dye-sensitized solar cell (DSC) using WO(2) as a counter electrode (CE) reached a high energy conversion efficiency of 7.25%, which can match the performance of the DSC based on a Pt CE.

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