Yantao Shi

Hole-Conductor-Free, Metal-Electrode-Free TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on a Low-Temperature Carbon Electrode

Low cost, high efficiency, and stability are straightforward research challenges in the development of organic-inorganic perovskite solar cells. Organolead halide is unstable at high temperatures or in some solvents. The direct preparation of a carbon layer on top becomes difficult. In this study, we successfully prepared full solution-processed low-cost TiO2/CH3NH3PbI3 heterojunction (HJ) solar cells based on a low-temperature carbon electrode. Power conversion efficiency of mesoporous (M-)TiO2/CH3NH3PbI3/C HJ solar cells based on a low-temperature-processed carbon electrode achieved 9%. The devices of M-TiO2/CH3NH3PbI3/C HJ solar cells without encapsulation exhibited advantageous stability (over 2000 h) in air in the dark. The ability to process low-cost carbon electrodes at low temperature on top of the CH3NH3PbI3 layer without destroying its structure reduces the cost and simplifies the fabrication process of perovskite HJ solar cells. This ability also provides higher flexibility to choose and optimize the device, as well as investigate the underlying active layers.

Low-cost and high-performance CoMoS4 and NiMoS4 counter electrodes for dye-sensitized solar cells

Porous chalcogels CoMoS4 and NiMoS4 made by a facile solution reaction displayed good electrocatalytic activity in the redox reaction of the I(-)/I3(-) shuttle. Dye-sensitized solar cells with these ternary compounds as counter electrodes (CEs) showed photovoltaic performance similar to the devices made with noble metal platinum CE (7.46%).

Low-Temperature and Solution-Processed Amorphous WO(x) as Electron-Selective Layer for Perovskite Solar Cells.

The electron-selective layer (ESL) is an indispensable component of perovskite solar cells (PSCs) and is responsible for the collection of photogenerated electrons. Preparing ESL at a low temperature is significant for future fabrication of flexible PSCs. In this work, solution-processed amorphous WO(x) thin film was prepared facilely at low temperature and used as ESL in PSCs. Results indicated that a large quantity of nanocaves were observed in the WO(x) thin film. In comparison with the conventional TiO2 ESL, the WO(x) ESL exhibited comparable light transmittance but higher electrical conductivity. Compared with the TiO2-based PSCs, PSCs that use WO(x) ESL exhibited comparable photoelectric conversion efficiency, larger short-circuit current density, but lower open-circuit voltage. Electrochemical characterization indicated that the unsatisfied open-circuit voltage and fill factor were caused by the inherent charge recombination. This study demonstrated that this material is an excellent candidate for ESL.

The Power of Single‐Atom Catalysis

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.

Amorphous Inorganic Electron-Selective Layers for Efficient Perovskite Solar Cells: Feasible Strategy Towards Room-Temperature Fabrication.

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.

Solid‐State Synthesis of ZnO Nanostructures for Quasi‐Solid Dye‐Sensitized Solar Cells with High Efficiencies up to 6.46%

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.

Notable catalytic activity of oxygen-vacancy-rich WO2.72 nanorod bundles as counter electrodes for dye-sensitized solar cells

For the first time, nonstoichiometric WO2.72 was used as a counter electrode (CE) in dye-sensitized solar cells (DSSCs). Oxygen-vacancy-rich WO2.72 nanorod bundles with notable catalytic activity for triiodide and thiolate reduction were prepared in this study. The photovoltaic parameters of dye-sensitized solar cells (DSSCs) with WO2.72 nanorod bundles as CEs are superior compared with those of the WO3-based cells, and nearly the same as those of the precious metal Pt-based cells. In a non-corrosive organic redox couple, the performance of WO2.72 CEs is better than that of Pt and WO3 CEs in DSSCs.

Atomically thin MoSe2/graphene and WSe2/graphene nanosheets for the highly efficient oxygen reduction reaction

As a conceptually new class of 2D materials, inorganic graphene analogue (IGA) ultrathin nanosheets perform an increasingly vital function in various electronic devices. However, the relatively low electrical conductivity of IGA ultrathin nanosheets severely hampers their application as electrode materials in devices. Through in situ synthesis, we report the combination of inorganic graphene and graphene into atomically thin nanosheets as efficient electrocatalysts for the oxygen reduction reaction (ORR). Benefitting from the advantages of both IGAs and reduced graphene oxide, the g–MoSe2 and g–WSe2 nanocomposites showed excellent ORR activity associated with a number of exchanged electrons close to four, which corresponded to the complete reduction of oxygen into water. In particular, the two electrocatalysts exhibited a positive onset potential of −0.02 V (close to that of Pt/C, 0.02 V) and a high kinetic current density (JK) of 10.22 mA cm−2 for g–MoSe2 and 10.77 mA cm−2 for g–WSe2 at −0.20 V. Compared with commercial Pt/C, these catalysts possess outstanding long-term durability and fuel crossover resistance capacity in alkaline media. Therefore, nanocomposites of inorganic graphene and graphene can be developed into low-cost and efficient alternatives (to the noble metal Pt) to be used as cathodic electrodes in fuel cells.

Optimizing nanosheet-based ZnO hierarchical structure through ultrasonic-assisted precipitation for remarkable photovoltaic enhancement in quasi-solid dye-sensitized solar cells

For ZnO hierarchical structures composed of interlaced nanosheets, it has been proved that they are more favorable for electron transportation in the photoanodes of ZnO-based dye-sensitized solar cells (DSCs). Here, we introduce ultrasonic-assisted precipitation for fabricating novel nanosheet-based ZnO hierarchical flowers (HFs) in aqueous solution. With the powerful ultrasound irradiation, these nanosheets on the HFs are not only interlaced and monocrystalline, but also axially oriented, porous and ultrathin. Furthermore, broad channels enclosed by adjacent nanosheets can deeply extend into the inner parts of the HFs. Structural improvements reveal that the specific area of the novel HFs as well as their performances on light-capturing and electron transport have been largely improved compared with those prepared through direct precipitation. Remarkably, when assembled into quasi-solid DSCs, ZnO HF photoanodes show a high conversion efficiency up to 6.19% (under AM 1.5, 100 mW cm−2 illumination), the highest record of quasi-solid ZnO-based DSCs up to now.

Single‐Atom Catalysis in Mesoporous Photovoltaics: The Principle of Utility Maximization

FeOx -supported single Pt atoms are used for the first time as counter electrodes (CEs) in dye-sensitized solar cells (DSCs), which are mesoporous photovoltaic devices. This system enables the investigation of the electrocatalytic behavior of a single-atom catalyst (SAC). Compared with conventional Pt CEs, the SAC-based CEs exhibit better reversibility as indicated by the peak-to-peak separation (Epp ). A high degree of atom utilization is demonstrated.