Although sunlight-driven water splitting is a promising route to sustainable hydrogen fuel production, widespread implementation is hampered by the expense of the necessary photovoltaic and photoelectrochemical apparatus. Here, we describe a highly efficient and low-cost water-splitting cell combining a state-of-the-art solution-processed perovskite tandem solar cell and a bifunctional Earth-abundant catalyst. The catalyst electrode, a NiFe layered double hydroxide, exhibits high activity toward both the oxygen and hydrogen evolution reactions in alkaline electrolyte. The combination of the two yields a water-splitting photocurrent density of around 10 milliamperes per square centimeter, corresponding to a solar-to-hydrogen efficiency of 12.3%. Currently, the perovskite instability limits the cell lifetime.

Researchers developed a perovskite solar cell with high power-conversion efficiency (>20%) and intense electroluminescence yield (0.5%).

TiO 2 /FTO, the cross sectional scanning electron microscopy (SEM) image of which is shown in Fig. 1a. Employing this solar cell configuration, we achieve the best PCE of 21.6% with a PMMA concentration C PMMA =0.6mg/ml. The photovoltaic metrics of the device are as follows: short-circuit current density (J SC ) = 23.7 mA cm -2 , open circuit voltage (V OC ) = 1.14 V, and a fill factor (FF) = 0.78 (Fig. 1b). One of the devices was sent for certification to Newport Corporation PV Lab, an accredited PV testing laboratory, confirming a PCE of 21.02% (supplementary Fig.1 Fig. 3, Tab. 2a and 2b). The photovoltaic metrics of the PSCs fabricated from PTNG method varying C PMMA are summarized in Fig. 1c.Upon increasing the PMMA concentrations (C PMMA , mg/ml) in mixed chlorobenzene and toluene (volume ratio of cholorobenzene and toluene is 9:1) solution, the PCE first augments and subsequently decreases with a peak at C PMMA = 0.6. Upon increasing the C PMMA from 0 to 0.6 mg/ml, the V oc rises from 1.10V to 1.14 V, and the FF from 0.74 to 0.78. To further examine the crystal structure, we conducted thin layer X-ray diffraction (XRD) measurements for perovskite films deposited on m-TiO 2 /blTiO 2 /FTO substrates (Fig.3a). The peak at 12.5 o arises from the (001) lattice planes of hexagonal (2H polytype) PbI 2. The excess PbI 2 is believed to passivate surface defects, increasing the solar cell performance 13 . All the samples show the same trigonal perovskite phase with the dominant (111) lattice reflection. We speculate the (111) plane to exhibit the smallest surface energy because the majority of grains exhibit this orientation to minimize the total Gibbs free energy of the system. With increasing C PMMA , the (111) oriented grains grew faster by consuming neighboring non-oriented crystals, either by regular grain growth or grain attachment, as evidenced by the increased ratio between the (111) and (123) peak at 13.9 ° and 31.5° in the presence of PMMA. By taking the full width at half maximum (FWHM) of the (111) reflection, we calculate the crystallite size using Scherrer's equation. Their dimension increases from 41 to 55, 70, 94, and 112 nm by increasing C PMMA from 0 to 4mg/ml.We attribute the larger crystal sizes to the templating effect of PMMA on the crystal The X-ray photoelectron spectroscopy (XPS) in Fig. 3d shows Pb 4f spectra.There are two main peaks Pb 4f7/2 and Pb 4f5/2 at 138 and 142.8 eV, respectively.We attribute the two small peaks located at 136.4 and 141.3 eV to the presence of In conclusion, we introduce a new method for preparing high-electronic quality perovskite films and implement it for the fabrication of PSC with excellent performance their certified PCE attaining 21 %. Further development of the method will enable further performance gains. Acknowledgement:

Metal halide perovskite solar cells (PSCs) currently attract enormous research interest because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication costs, but their practical development is hampered by difficulties in achieving high performance with large-size devices. We devised a simple vacuum flash-assisted solution processing method to obtain shiny, smooth, crystalline perovskite films of high electronic quality over large areas. This enabled us to fabricate solar cells with an aperture area exceeding 1 square centimeter, a maximum efficiency of 20.5%, and a certified PCE of 19.6%. By contrast, the best certified PCE to date is 15.6% for PSCs of similar size. We demonstrate that the reproducibility of the method is excellent and that the cells show virtually no hysteresis. Our approach enables the realization of highly efficient large-area PSCs for practical deployment.

A mixture of CsPbI3 and FAPbI3 is thermodynamically stabilized in the perovskite phase with respect to the pure δ phases.

In the past few years, organic-inorganic halide perovskites have rapidly emerged as promising materials for photovoltaic applications, but simultaneously achieving high performance and long-term stability has proved challenging. Here, we show a one-step solution-processing strategy using phosphonic acid ammonium additives that results in efficient perovskite solar cells with enhanced stability. We modify the surface of methylammonium lead triiodide (CH3NH3PbI3) perovskite by spin-coating its precursor solution in the presence of butylphosphonic acid 4-ammonium chloride. Morphological, structural and elemental analyses show that the phosphonic acid ammonium additive acts as a crosslink between neighbouring grains in the perovskite structure, through strong hydrogen bonding of the -PO(OH)2 and -NH3(+) terminal groups to the perovskite surface. The additives facilitate the incorporation of the perovskite within a mesoporous TiO2 scaffold, as well as the growth of a uniform perovskite layer at the surface, enhancing the material's photovoltaic performance from 8.8 to 16.7% as well as its resistance to moisture.

Fe3O4 has long been regarded as a promising anode material for lithium ion battery due to its high theoretical capacity, earth abundance, low cost, and nontoxic properties. However, up to now no effective and scalable method has been realized to overcome the bottleneck of poor cyclability and low rate capability. In this article, we report a bottom-up strategy assisted by atomic layer deposition to graft bicontinuous mesoporous nanostructure Fe3O4 onto three-dimensional graphene foams and directly use the composite as the lithium ion battery anode. This electrode exhibits high reversible capacity and fast charging and discharging capability. A high capacity of 785 mAh/g is achieved at 1C rate and is maintained without decay up to 500 cycles. Moreover, the rate of up to 60C is also demonstrated, rendering a fast discharge potential. To our knowledge, this is the best reported rate performance for Fe3O4 in lithium ion battery to date.

Although large research efforts have been devoted to photoelectrochemical (PEC) water splitting in the past several decades, the lack of efficient, stable and Earth-abundant photoelectrodes remains a bottleneck for practical application. Here, we report a photocathode with a coaxial nanowire structure implementing a Cu 2 O/Ga 2 O 3-buried p-n junction that achieves efficient light harvesting across the whole visible region to over 600 nm, reaching an external quantum yield for hydrogen generation close to 80%. With a photocurrent onset over + 1 V against the reversible hydrogen electrode and a photocurrent density of ~10 mA cm −2 at 0 V versus the reversible hydrogen electrode, our electrode constitutes the best oxide photocathode for catalytic generation of hydrogen from sunlight known today. Conformal coating via atomic-layer deposition of a TiO 2 protection layer enables stable operation exceeding 100 h. Using NiMo as the hydrogen evolution catalyst, an all Earth-abundant Cu 2 O photocathode was achieved with stable operation in a weak alkaline electrolyte. To show the practical impact of this photocathode, we constructed an all-oxide unassisted solar water splitting tandem device using state-of-the-art BiVO 4 as the photoanode, achieving ~3% solar-to-hydrogen conversion efficiency.