This study successfully demonstrates the application of inorganic p-type nickel oxide (NiOx ) as electrode interlayer for the fabrication of NiOx /CH3 NH3 PbI3 perovskite/PCBM PHJ hybrid solar cells with a respectable solar-to-electrical PCE of 7.8%. The better energy level alignment and improved wetting of the NiOx electrode interlayer significantly enhance the overall photovoltaic performance.

extensive research efforts have been dedicated to develop effi cient OER electrocatalysts with high activity and low overpotential. [ 3 ] Among which, noble metal-based oxides, such as ruthenium oxide and iridium oxide, are regarded as the best OER electrocatalysts, [ 4 ] but the scarcity of ruthenium and iridium limits their widespread applications. Accordingly, materials based on fi rst-row transition metal oxides that are naturally abundant and catalytically active have received considerable attention, since these metal oxide materials show great promises as alternative electrocatalysts for OER. [ 5 ] For example, cobalt-based materials such as Co(PO 3 ) 2 , [ 6 ] Co 3 O 4 , [ 7 ] NiCo 2 O 4 , [ 8 ] Zn X Co 3-X O 4 , [ 9 ] Mn-Co oxide, [ 10 ] and Ni X Co 3-X O 4 [ 11 ] have been extensively studied as competent electrocatalysts for water oxidation reaction because of their good catalytic activity and excellent stability under oxidizing conditions in alkaline medium. Catalytic reaction commonly takes place on the surface of a catalyst, which indicates that activities of electrocatalysts can be strongly infl uenced by the geometric structure. Furthermore, cobaltbased oxides for OER are usually employed in the form of thin fi lms or agglomerates bound together by polymer binders, [ 12 ] which leads to the low surface area and ineffective electronmass transfer and signifi cantly restricts the electrocatalytic activity due to poor contact between active material/electrolyte and boundaries among particles. As a result, it is highly desirable to design 3D electrocatalysts with large surface area, good electroconductivity, and high porosity for OER. [ 9,13 ] In the present work, we report a solution chemical method to construct a Ni-Co oxide (NCO) OER electrocatalyst with unique hierarchical 3D nanosheets (HNSs) structure. The NCO-HNSs showed high surface area with a Ni 3+ -rich surface, delivering a stable current density of 10 mA cm −2 for OER at an overpotential of ≈0.34 V with a Tafel slope of 51 mV dec −1 . The improved OER activity of NCO-HNSs as compared with other cobaltbased oxide counterparts such as Co 3 O 4 nanorods (Co 3 O 4 -NRs), Co 3 O 4 nanosheets (Co 3 O 4 -NSs), and Ni-Co oxide nanorods (NCO-NRs) can be ascribed to the synergy of Ni 3+ -enriched surface which facilitates the formation of NiOOH as active sites for improving the catalytic reaction and the high surface area offered by the unique 3D hierarchical nanostructure.Effi cient and earth abundant electrocatalysts for high-performance oxygen evolution reaction (OER) are essential for the development of sustainable energy conversion technologies. Here, a new hierarchical Ni-Co oxide nanostructure, composed of small secondary nanosheets grown on primary nanosheet arrays, is synthesized via a topotactic transformation of Ni-Co layered double hydroxide. The Ni 3+ -rich surface benefi ts the formation of NiOOH, which is the main redox site as revealed via in situ X-ray absorption near edge structure and extended X-ray absorption fi ne structure ...

A flexible cloth-like electrode, which can efficiently split water to produce H2 at neutral pH, is successfully demonstrated.

Electrochemically converting water into oxygen/hydrogen gas is ideal for high-density renewable energy storage in which robust electrocatalysts for efficient oxygen evolution play crucial roles. To date, however, electrocatalysts with long-term stability have remained elusive. Here we report that single-crystal Co3O4 nanocube underlay with a thin CoO layer results in a high-performance and high-stability electrocatalyst in oxygen evolution reaction. An in situ X-ray diffraction method is developed to observe a strong correlation between the initialization of the oxygen evolution and the formation of active metal oxyhydroxide phase. The lattice of skin layer adapts to the structure of the active phase, which enables a reversible facile structural change that facilitates the chemical reactions without breaking the scaffold of the electrocatalysts. The single-crystal nanocube electrode exhibits stable, continuous oxygen evolution for >1,000 h. This robust stability is attributed to the complementary nature of defect-free single-crystal electrocatalyst and the reversible adapting layer.

The decomposition of methanol catalyzed with Rh nanoclusters supported on an ordered thin film of Al2O3/NiAl­(100) became enhanced on decreasing the size of the clusters. The decomposition of methanol (and methanol-d 4) proceeded through dehydrogenation; the formation thereby of CO became evident above 200 K, depending little on the cluster size. In contrast, the production of CO and hydrogen (deuterium) from the reaction varied notably with the cluster size. The quantity of either CO or hydrogen produced per Rh surface site was unaltered on clusters of diameter >1.5 nm and height >0.6 nm, corresponding to about 65% of methanol undergoing decomposition on adsorption in a monolayer on the clusters. For clusters of diameter <1.5 nm and height <0.6 nm, the production per Rh surface site increased with decreasing size, up to 4 times that on the large clusters or Rh(100) single-crystal surface. The reactivity was enhanced largely because, with decreasing cluster size, the activation energy for the scission of the O–H bond in the initial dehydrogenation became smaller than the activation energy for the competing desorption. The property was associated with the edge Rh atoms at the surface of small clusters.

Red-green-blue (RGB) full-color micro light-emitting diodes (μ-LEDs) fabricated from semipolar (20-21) wafers, with a quantum-dot photoresist color-conversion layer, were demonstrated. The semipolar (20-21) InGaN/GaN μ-LEDs were fabricated on large (4 in.) patterned sapphire substrates by orientation-controlled epitaxy. The semipolar μ-LEDs showed a 3.2 nm peak wavelength shift and a 14.7% efficiency droop under 200    A / cm 2 injected current density, indicating significant amelioration of the quantum-confined Stark effect. Because of the semipolar μ-LEDs’ emission-wavelength stability, the RGB pixel showed little color shift with current density and achieved a wide color gamut (114.4% NTSC space and 85.4% Rec. 2020).

The band-edge levels of CdS-, CdSe-, and CdS/CdSe-sensitized TiO2 electrodes were determined by ultraviolet photoelectron spectroscopy (UPS) to explore the reason leading to the high performance of the TiO2/CdS/CdSe electrode. The obtained UPS results show the stepwise energy level in the TiO2/CdS/CdSe electrode, indicating energy level alignment occurrence between CdS and CdSe in the TiO2/CdS/CdSe. Time-resolved photoluminescence and open-circuit photovoltage decay experiments reveal that the photogenerated electrons in the TiO2/CdS/CdSe have higher injection efficiency, but lower recombination rate to the electrolyte, attributable to the stepwise structure of band-edge levels constructed by the effect of the energy level alignment.

Photovoltaic performance of a perovskite solar cell is observed to decrease with increasing humidity, which might be attributed to the formation of hydrated intermediates leading to a decrease in extraction of photocarriers. However, direct evidence of the interplay between the perovskite layer and the photovoltaic performance under operating conditions (consecutive illumination) has not yet been reported. Herein, we investigated the degradation of perovskite solar cells under operating situations through in situ X-ray diffraction and in situ X-ray absorption spectroscopies, which revealed that lead hydroxide iodide (PbIOH), a new phase that has not previously been identified as the degradation product of perovskite solar cells, was formed as an end decomposition product inside the cell. The formation of PbIOH could break the interface inside and be the key reason behind the problem of reduced cell life. This work illustrates that in operando direct observation of the photo-and moisture-induced effects can provide needed insights toward realizing stable perovskite solar cells.