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Developing a cost‐saving, high‐efficiency, and simple synthesis of counter electrode (CE) material to replace pricy Pt for dye‐sensitized solar cells (DSSCs) has become a research hotspot. Owing to the electronic coupling effects between various components, semiconductor heterostructures can significantly enhance the catalytic performance and endurance of counter electrodes. However, the strategy to controllably synthesize the same element in several phase heterostructures used as the CE in DSSCs is still absent. Here, we fabricate well‐defined CoS2/CoS heterostructures and use them as CE catalysts in DSSCs. The as‐designed CoS2/CoS heterostructures display high catalytic performance and endurance for the triiodide reduction in DSSCs thanks to the combined and synergistic effects. As a result, a DSSC with CoS2/CoS achieves a high energy conversion with an efficiency of 9.47 % under standard simulated solar radiation, surpassing that of pristine Pt‐based CE (9.20 %). Besides, the CoS2/CoS heterostructures possess a quick activity initiation process and extended stability, broadening their potential applications in various areas. Therefore, our proposed synthetic approach could offer new insights for synthesizing functional heterostructure materials with improved catalytic activities in DSSCs. [ABSTRACT FROM AUTHOR]

If counter electrodes (CEs) could also contribute to light harvesting in dye‐sensitized solar cells (DSSCs), then the power conversion efficiency (PCE) of DSSCs would be further boosted without changing the device structure. Nearly monodispersed Ag2Se nanocrystals with a bandgap of 1.62 eV (∼765 nm) were synthesized via a one‐pot process, and Ag2Se CEs were fabricated by using a spin‐coating and annealing process. Incident photon‐to‐current conversion efficiency and photocurrent spectra indicated that Ag2Se CEs can generate the electricity by harvesting more visible light, which could not be absorbed by dye‐sensitized photoanodes. Thus, compared to Pt CE (7.57 %), the DSSC based on Ag2Se CE exerted a higher PCE of 8.06 %. The development of photovoltaic CEs may offer an alternative way to promote the performance and competitiveness of DSSCs. Photovoltaic counter electrodes not only catalyse I3− reduction, but also harvest transmitted photons of photoanodes to increase the photocurrent of DSSCs (see figure). This offers an alternative method for enhancing the performance and competitiveness of DSSCs. [ABSTRACT FROM AUTHOR]

Abstract: The electrocatalytic performances of semiconductors are closely correlated to their energy structures, and solid solutions can continuously tune the energy structures by controlling their composition. Herein, a series of Fe1‐xCoxS2 (x=0–0.5) solid solutions have been synthesized and served as counter electrodes in dye‐sensitized solar cells (DSSCs). The Fermi level of Fe1‐xCoxS2 solid solutions shifted negatively as the x value changed from 0 to 0.5, and the electrocatalytic performance for I3− reduction gradually enhanced due to the facilitated electron transfer process from electrode to I3−. Benefitting from its negative Fermi level, Fe0.5Co0.5S2 exhibited the smallest charge transfer resistance (Rct) and remarkable electrocatalytic properties. The DSSCs using Fe0.5Co0.5S2 as a counter electrode achieve the lowest Rct (0.84 Ω cm2) and the highest power conversion efficiency (η=8.36%) of these solid solution materials. [ABSTRACT FROM AUTHOR]

Metal-semiconductor based Mott-Schottky (M-S) heterojunctions combining two or more functionalities in one unit can effectively improve their catalytic activity and durability due to the electronic coupling effects between distinct components. Although tremendous progress has been made in structure fabrication, controllable synthesis of one-dimensional (1D) M-S heterojunction and its application as electrocatalysts is still lacking. Herein, uniform and well-defined 1D Ni 3 S 4 -PtCo heteronanorods are synthesized via a facile solution method and employed as counter electrode (CE) catalyst in the dye-sensitized solar cells (DSSCs). By exploiting the benefits of both structural and compositional characteristics, namely, the direct electrical pathways of 1D nanostructure, optimized work function of metal alloy as well as the synergistic effect between Ni 3 S 4 and PtCo, the as-designed Ni 3 S 4 -PtCo heteronanorods exhibit excellent catalytic activity and stability toward the reduction of triiodide in DSSCs. A DSSC with Ni 3 S 4 -PtCo achieves a high power conversion efficiency of 8.66% under AM1.5G illumination (100 mW cm −2 ), higher than that of pristine Pt-based device (8.12%). Moreover, the fast activity onset and relatively long stability further demonstrate that the Ni 3 S 4 -PtCo heteronanorod is a promising alternative to Pt in DSSCs. Considering the diversity of structures and components in heterostructures, the strategy presented here can be extended for synthesizing other well-defined 1D M-S heterojunctions, which may be used in the fields of catalysis, energy conversion and storage. [ABSTRACT FROM AUTHOR]