Organic–inorganic hybrid perovskite solar cells (PSCs) have become a promising candidate in the photovoltaic field due to their high power conversion efficiency and low material cost. However, the ...development of PSCs is limited by their poor stability under practical conditions in the presence of oxygen, moisture, sunlight, heat, and the current–voltage (I–V) hysteresis. In particular, the hysteretic I–V issue casts doubt on the validity of the photovoltaic performance results that are achieved, making it difficult to evaluate the authentic performance of PSCs. This review article focuses on understanding the I–V hysteresis behavior in PSCs and on exploring the possible reasons leading to this hysteresis phenomenon. The various strategies attempted to suppress the I–V hysteresis in PSCs are summarized, and a brief future recommendation is provided.
One of the problems that restrict the further development of perovskite solar cells (PSCs) is hysteresis, making it difficult to evaluate the reliable performance of PSCs. Recent process regarding the strategies to efficiently reduce hysteresis in PSCs is reviewed. The influential factors and possible reasons are also outlined.
The organic-inorganic hybrid perovskite CH
3
NH
3
PbI
3
is a novel light harvester, which can greatly improve the solar-conversion efficiency of dye-sensitized solar cells. In this article, a ...first-principle theoretical study is performed using local, semi-local and non-local exchange-correlation approximations to find a suitable method for this material. Our results, using the non-local optB86b + vdWDF functional, excellently agree with the experimental data. Thus, consideration of weak van der Waals interactions is demonstrated to be important for the accurate description of the properties of this type of organic-inorganic hybrid materials. Further analysis of the electronic properties reveals that I 5p electrons can be photo-excited to Pb 6p empty states. The main interaction between the organic cations and the inorganic framework is through the ionic bonding between CH
3
and I ions. Furthermore, I atoms in the Pb-I framework are found to be chemically inequivalent because of their different chemical environments.
The properties of organic-inorganic hybrid orthorhombic perovskite CH
3
NH
3
PbI
3
materials have been theoretically investigated with consideration of van der Waals interactions.
Earth-abundant first-row (3d) transition metal–based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodynamic ...requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 millivolts) reported at 10 milliamperes per square centimeter in alkaline electrolyte. The catalyst shows no evidence of degradation after more than 500 hours of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER.
The electrocatalytic reduction of CO
2
presents a promising strategy in addressing environmental and energy crisis. Significant progress has been achieved via CO
2
gas diffusion electrolysis, to ...react at high selectivity and high rate. However, the gas diffusion layer (GDL) of the gas diffusion electrode (GDE) still suffers from low tolerance and limited active sites. Here, the hydrophobic 1-octadecanethiol molecular was functionalized over the Cu catalyst layer of the GDE, which simultaneously stabilizes the GDL and exposes abundant active solid-liquid-gas three-phase interfaces. The resultant GDE exhibits multi-carbon (C
2+
) product selectivity over faradaic efficiency (FE) of 70.0% in the range of 100 to 800 mA·cm
−2
, with the peak FE
C2+
of 85.2% at 800 mA·cm
−2
. Notably, the strengthened GDE could continuously drive high-current electrolysis for more than 100 h without flooding. This work opens a new way to improve CO
2
gas diffusion electrolysis via surface molecular engineering.
Dye-sensitized solar cells (DSSCs) are expected to be a powerful competitor of conventional silicon devices due to their simple, low-cost, and pollution-free processing. Platinum (Pt) as commonly ...used counter electrode (CE) material is, however, limited to its expensive cost and undesired reverses. The development of an efficient Pt-free CE material with high electrical conductivity and excellent electrocatalytic activity is a feasible strategy to solve the above limitations. Herein, we have proposed a simple two-step strategy to synthesize hierarchical Co
3
O
4
/graphene oxide composite catalysts. The as-prepared nanoporous Co
3
O
4
cubes with hierarchical architecture may provide a mass of electrocatalytic activity sites. The combination of hierarchical structures and graphene oxide may enable the electrons to rapidly transfer on the submicron-sized graphene oxide. As a novel and low-cost CE material, DSSCs based on hierarchical Co
3
O
4
/graphene oxide composite exhibit photovoltaic performance comparable to the traditional Pt CE. This is due to the ideal combination of excellent electrocatalytic activity and high conductivity. Our finding provides a judicious strategy for nanoscale synthesis of hierarchical composites and may facilitate the preparation of efficient and low-cost CE materials for DSSCs.
The activity and durability of electrocatalysts are important factors in their practical applications, such as electrocatalytic oxygen evolution reactions （OERs） used in water splitting cells and ...metal-air batteries. In this study, a novel electrocatalyst, comprising few-layered graphitic carbon （-5 atomic layers） encapsulated heazlewoodite （Ni3S2@C） nanoparticles （NPs）, was designed and synthesized using a one-step solid phase pyrolysis method. In the OER test, the Ni3S2@C catalyst exhibited an overpotential of 298 mV at a current density of 10 mA·cm^-2, a Tafel slope of 51.3 mV·dec^-1, and charge transfer resistance of 22.0 Ω, which were better than those of benchmark RuO2 and most nickel- sulfide-based catalysts previously reported. This improved performance was ascribed to the high electronic conductivity of the graphitic carbon encapsulating layers. Moreover, the encapsulation of graphitic carbon layers provided superb stability without noticeable oxidation or depletion of Ni3S2 NPs within the nanocomposite. Therefore, the strategy introduced in this work can benefit the development of highly stable metal sulfide electrocatalysts for energy conversion and storage applications, without sacrificing electrocatalytic activity.
Here we report a hydrothermal approach to build and tailor the hierarchical structure of brookite TiO2 crystal under multiple hierarchical scales. Benefiting from the hierarchical structure and the ...existence of oxygen vacancy, these as-prepared hierarchical brookite TiO2 crystals can not only enhance photocatalytic activity, but also demon- strate their potential in the treatment of superficial malig-nant tumor.
Metal-organic frameworks (MOFs) possess the features of highly porosity-tunable and electronic-tunable structures. Taking advantages of these merits, we successfully installed high-valence W
6+
ions ...onto the Ti-oxo clusters of MIL-125(Ti) (W-MIL-125). The installed W
6+
ions which form a W-O-Ti structure trigger the metal-to-cluster charge transfer (MCCT), together with an enhanced light absorption. Structural and spectroscopic characterizations reveal that the MCCT process optimizes the charge transfer process and efficiently separates the photogenerated electron-hole spatially. The as-obtained sample of 3.45 W-MIL-125 with optimized electronic structure demonstrates an enhanced photocatalytic hydrogen evolution performance of 1110.7 ± 63.7 µmol g
−1
h
−1
under light irradiation, which is 4.0 times that of the pristine MIL-125(Ti). This work will open up a new avenue for local structural modification of MOFs to boost photocatalytic performance.
Bismuth vanadate （BiVO4） has been identified as one of the excellent visible-light-responsive photoanode for use in the photoelectrochemical water splitting. Recently intense research efforts have ...been devoted to the development of highly efficient BiVO4 photoanode. Herein, we reported a low-cost and scalable method for preparing nanostructured BiVO4 film. A much enhanced photocurrent （1.5 mAocm 2） was obtained for such film, which was 6.5 times higher than that of planar film at 1.23 V vs. RHE （Reversible Hydrogen Electrode）. The method provides an eco-friendly, reproducible and facile way to scale up on different substrates with attractive potential.
Anatase TiO2 as a promising photocatalyst has been widely employed in the decontamination treatment of polluted water, air purification and water splitting. Coupling TiO2 with other semiconductor ...materials could further enhance the photocatalytic activity. Here, we successfully synthesized the SnOz/TiO2 catalyst by depositing SnO2 particles on the anatase TiO2 {105} facets through a gas phase oxidation process. The SnOz/TiO2 catalyst shows higher photocatalytic activity for decomposition of MB than that of the pure YiO2 catalyst. The enhanced photo- catalytic activity can be attributed to the efficient charge separation since TiO2 and SnO2 catalyst have staggered energy level.
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