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Inorganic electron-selective layers (ESLs) are fabricated at extremely low temperatures of 70°C or even 25°C by a simple solution route. This is of great significance because the attained PCEs confirm the feasibility of room-temperature coating of inorganic amorphous ESLs through a solution method for the first time.

Single-atom catalysts (SACs) are a frontier research topic in the catalysis community. Carbon materials decorated with atomically dispersed Ti are theoretically predicted with many attractive applications. However, such material has not been achieved so far. Herein, a Ti-based SAC, consisting of isolated Ti anchored by oxygen atoms on reduced graphene oxide (rGO) (termed as Ti1 /rGO), is successfully synthesized. The structure of Ti1 /rGO is characterized by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy, being determined to have a five coordinated local structure TiO5 . When serving as non-Pt cathode material in dye-sensitized solar cells (DSCs), Ti1 /rGO exhibits high electrocatalytic activity toward the tri-iodide reduction reaction. The power conversion efficiency of DSCs based on Ti1 /rGO is comparable to that using conventional Pt cathode. The unique structure of TiO5 moieties and the crucial role of atomically dispersed Ti in Ti1 /rGO are well understood by experiments and density functional theory calculations. This emerging material shows potential applications in energy conversion and storage devices.

Single-atom catalysts (SACs) with individual and isolated metal atoms anchored to supports can act as active centers. Single-atom catalysis is powerful and attractive because SACs have demonstrated distinguishing performances, such as drastic cost-reduction, notable catalytic activity, and selectivity. Herein, we firstly introduce SAC, including the concept and some key issues in synthesis and catalysis. Then, the power of single-atom catalysis is highlighted and the most recent advances are summarized. It is very encouraging that in recent years our understanding of SACs has increased, owing to substantial studies regarding sample preparation, characterization, evaluation, and also mechanistic interpretation. On the other hand, great challenges still remain for SACs.

Electron transport layer (ETL) is a functional layer of great significance for boosting the power conversion efficiency (PCE) of perovskite solar cells (PSCs). To date, it is still a challenge to simultaneously reduce the surface defects and improve the crystallinity in ETLs during their low-temperature processing. Here, a novel strategy for the mediation of in situ regrowth of SnO2 nanocrystal ETLs is reported: introduction of controlled trace amounts of surface absorbed water on the fluorinated tin oxide (FTO) or indium-tin oxide (ITO) surfaces of the substrates using ultraviolet ozone (UVO) pretreatment. The optimum amount of adsorbed water plays a key role in balancing the hydrolysis-condensation reactions during the structural evolution of SnO2 thin films. This new approach results in a full-coverage SnO2 ETL with a desirable morphology and crystallinity for superior optical and electrical properties, as compared to the control SnO2 ETL without the UVO pretreatment. Finally, the rigid and flexible PSC devices based on the new SnO2 ETLs yield high PCEs of up to 20.5% and 17.5%, respectively.

Solid-state synthesis of ZnO nanostructured building blocks is presented in this work for the fabrication of high efficiency quasi-solid dye-sensitized solar cells (DSSCs). The sponge-like photoanode has high optical density and better connections. Baking the photoanode at low temperature, photoconversion efficiencies of up to 6.46% are yielded by the quasi-solid DSSCs. Furthermore, we demonstrate better stability of our ZnO quasi-solid DSSCs.

Single-atom catalysts (SACs) with individual and isolated metal atoms anchored to supports can act as active centers. Single-atom catalysis is powerful and attractive because SACs have demonstrated distinguishing performances, such as drastic cost-reduction, notable catalytic activity, and selectivity. Herein, we firstly introduce SAC, including the concept and some key issues in synthesis and catalysis. Then, the power of single-atom catalysis is highlighted and the most recent advances are summarized. It is very encouraging that in recent years our understanding of SACs has increased, owing to substantial studies regarding sample preparation, characterization, evaluation, and also mechanistic interpretation. On the other hand, great challenges still remain for SACs.

In this paper, a novel hierarchically structured ZnO photoanode for use in quasi-solid state dye-sensitized solar cells (DSCs) is presented. The film is composed of polydisperse spindle-shaped ZnO particles that are prepared through direct precipitation of zinc acetate in aqueous solution. Without additional pore-forming agents, the microporous structure is well constructed through the packing of polydisperse ZnO particles. In the film, small ZnO particles are able to improve interparticle connectivity and offer a large internal surface area for sufficient dye-adsorption; on the other hand, particles of larger size can enhance the occurrence of light-scattering and introduce micropores for the permeation of quasi-solid state electrolytes. Meanwhile, morphologies, particle size, and specific areas of the products are controlled by altering the reactant concentration and synthetic temperature. Combined with a highly viscous polymer gel electrolyte, a device based on this ZnO photoanode shows high conversion efficiencies, 4.0% and 7.0%, under 100 and 30 mW cm -2 illumination, respectively. Finally, the unsealed device is demonstrated to remain above 90% of its initial conversion efficiency after 7 days, showing excellent stability.