Band gap energies of solar micro/meso-porous composites of zinc (hydr)oxide with graphite oxides

Abstract

The band gap energies of micro/meso-porous zinc (hydr)oxide and its composites with 2 wt. % and 5 wt. % graphite oxides are reported using three optical characterization techniques. The obtained energy gaps (from 2.84 eV to 2.95 eV) of the composites are smaller than that for zinc oxide (∼3.2 eV) and zinc (hydr)oxide (∼3.06 eV). The band gap narrowing of the composite materials is due to the presence of defects, larger particle size, and weaker confinement. The bonds between zinc (hydr)oxide lattice and the carbon of graphene phase also contribute to this phenomenon. The structural properties of these materials are presented using Transmission Electron Microscopy, Scanning Tunneling Electron Microscopy, X-Ray analysis, and Two-Photon Fluorescence imaging Microscopy.

Key role of terminal hydroxyl groups and visible light in the reactive adsorption/catalytic conversion of mustard gas surrogate on zinc (hydr)oxides

“…The E g of ZnSA, ZnRA and ZnO C is 3.22 eV, 3.05 eV and 2.98 eV, respectively. While the E g of ZnRA and ZnO C are in the range of other ZnO materials reported in the literature [25], the ZnSA band gap energy represents a typical value found for zinc (hydr)oxides [26,27]. A wide band gap feature is an advantage of our materials, since this characteristic is beneficial for the development of optical and electronic devices [28].…”

The effects of fabrication temperature on current-voltage characteristics and energy efficiencies of quantum dot sensitized ZnOH-GO hybrid solar cells

“…The morphologies of zinc (hydr)oxide and its composites were previously reported using the images obtained by Two Photon Fluorescence (TPF) Microscopy, Scanning Electron Microscopy (SEM), and Scanning Tunneling Microscopy (STEM). [8][9][10][11] Third, graphite-oxide (GO) was synthesized by oxidation of graphite (Sigma-Aldrich) using Hummers method, detailed elsewhere. 8,12 Fourth, prior to chemical synthesis of ZnOH-GO composites, the structures of the precursor materials were investigated.…”

“…Using this imaging technique, particle size and their distribution were reported earlier. [9][10][11] TPF imaging was performed with the Ultima Multi-Photon-Microscope (Olympus BX-51 of Prairie Tech. Inc., WI, USA).…”

“…Presence of pores in the ZnOH-GO structure at room temperature was previously reported. 9,10 Changes in the texture and chemistry of the samples, due to an increase in fabrication temperature, observed are responsible for better performance of the solar cells. The initial samples of ZnOH-GO exhibit some porosity, especially in the mesoscopic range ($11.94 6 3.21 lm).…”

“…4,8 A large band gap of TiO 2 (3.0-3.23 eV) 4 and of zinc (hydr)oxide, Zn(OH) 2 , and its graphite oxide (GO)-based composite, such as ZnGO ($2.90 eV) 9 are suitable for their use in a dye-or QD-sensitized solar cells, because the band gap influences the efficiency of a solar cell. 4 Composite materials, such as zinc (hydr)oxide-graphite-oxides (ZnOH-GO) are synthesized using Zn(OH) 2 with GO, where GO has been identified as an interesting material for large scale graphene processing.…”