@article{went_wong_jahelka_kelzenberg_biswas_hunt_carbone_atwater_2019, title={A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics}, volume={5}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.aax6061}, abstractNote={We develop a new technique for transferring metal contacts to create ultrathin solar cells from 2D materials. Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin optoelectronic devices due to their high absorption coefficients and intrinsically passivated surfaces. To maintain these near-perfect surfaces, recent research has focused on fabricating contacts that limit Fermi-level pinning at the metal-semiconductor interface. Here, we develop a new, simple procedure for transferring metal contacts that does not require aligned lithography. Using this technique, we fabricate vertical Schottky-junction WS2 solar cells, with Ag and Au as asymmetric work function contacts. Under laser illumination, we observe rectifying behavior and open-circuit voltage above 500 mV in devices with transferred contacts, in contrast to resistive behavior and open-circuit voltage below 15 mV in devices with evaporated contacts. One-sun measurements and device simulation results indicate that this metal transfer process could enable high specific power vertical Schottky-junction transition metal dichalcogenide photovoltaics, and we anticipate that this technique will lead to advances for two-dimensional devices more broadly.}, number={12}, journal={SCIENCE ADVANCES}, author={Went, Cora M. and Wong, Joeson and Jahelka, Phillip R. and Kelzenberg, Michael and Biswas, Souvik and Hunt, Matthew S. and Carbone, Abigail and Atwater, Harry A.}, year={2019}, month={Dec} }
 @article{zoellner_o'donnell_wu_itanze_carbone_osterloh_geyer_maggard_2019, title={Impact of Nb(V) Substitution on the Structure and Optical and Photoelectrochemical Properties of the Cu-5(Ta1-xNbx)(11)O-30 Solid Solution}, volume={58}, ISSN={["1520-510X"]}, DOI={10.1021/acs.inorgchem.9b00304}, abstractNote={A family of solid solutions, Cu5(Ta1- xNb x)11O30 (0 ≤ x ≤ 0.4), was investigated as p-type semiconductors for their band gaps and energies and for their activity for the reduction of water to molecular hydrogen. Compositions from 0 to 40 mol % niobium were prepared in high purity by solid-state methods, accompanied by only very small increases in the lattice parameters of ∼0.05% and with the niobium and tantalum cations disordered over the same atomic sites. However, an increasing niobium content causes a significant decrease in the bandgap size from ∼2.58 to ∼2.05 eV owing to the decreasing conduction band energies. Linear-sweep voltammetry showed an increase in cathodic photocurrents with niobium content and applied negative potential of up to -0.6 mA/cm2 (pH ∼7.3; AM 1.5 G light filter with an irradiation intensity of ∼100 mW/cm2). The cathodic photocurrents could be partially stabilized by heating the polycrystalline films in air at 550 °C for 1 h to produce surface nanoislands of CuO or using protecting layers of aluminum-doped zinc oxide and titania. Aqueous suspensions of the Cu5(Ta1- xNb x)11O30 powders were also found to be active for hydrogen production under visible-light irradiation in a 20% aqueous methanol solution with the highest apparent quantum yields for the 10% and 20% Nb-substituted samples. Electronic structure calculations show that the increased photocurrents and hydroen evolution activities of the solid solutions arise near the percolation threshold of the niobate/tantalate framework wherein the Nb cations establish an extended -O-Nb-O-Nb-O- diffusion pathway for the minority carriers. The latter also reveals a novel pathway for enhancing charge separation as a function of the niobium-oxide connectivity. Thus, these results illustrate the advantages of using solid solutions to achieve the smaller bandgap sizes and band energies that are needed for solar-driven photocatalytic reactions.}, number={10}, journal={INORGANIC CHEMISTRY}, author={Zoellner, Brandon and O'Donnell, Shaun and Wu, Zongkai and Itanze, Dominique and Carbone, Abigail and Osterloh, Frank E. and Geyer, Scott and Maggard, Paul A.}, year={2019}, month={May}, pages={6845–6857} }
 @article{zoellner_hou_carbone_kiether_markham_cuomo_maggard_2018, title={Activating the Growth of High Surface Area Alumina Using a Liquid Galinstan Alloy}, volume={3}, ISSN={["2470-1343"]}, DOI={10.1021/acsomega.8b02442}, abstractNote={The growth of high surface area alumina has been investigated with the use of a liquid Galinstan alloy [66.5% (wt %) Ga, 20.5% In and 13.0% Sn] as an activator for aluminum. In this process, the aluminum is slowly dissolved into the gallium-indium-tin alloy, which is then selectively oxidized at ambient temperature and pressure under a humid stream of flowing CO2 or N2 to yield amorphous alumina. This preparative route represents a simple and low toxicity approach to obtain amorphous high surface area alumina with very low water content. The as-synthesized high surface area alumina aerogel was a blue-colored solid owing to the Rayleigh scattering by its dendritic fibrous nanostructure consisting of mainly alumina with small amounts of water. Upon annealing at 850 °C, the amorphous product transformed into γ-Al2O3, as well as θ-Al2O3 upon annealing at 1050 °C. Elemental analysis by energy-dispersive spectroscopy provides further evidence that the high surface area alumina is composed of only aluminum and oxygen. The surface area of the amorphous alumina varied from ∼79 to ∼140 m2/g, depending on the initial weight percentage of aluminum used in the alloy. A correlation between the initial concentration of aluminum in the alloy and the surface area of the alumina product was found to peak at ∼30% Al. These results suggest a novel route to the formation of amorphous alumina aerogel-type materials.}, number={12}, journal={ACS OMEGA}, author={Zoellner, Brandon and Hou, Feier and Carbone, Abigail and Kiether, William and Markham, Keith and Cuomo, Jerome and Maggard, Paul A.}, year={2018}, month={Dec}, pages={16409–16415} }