Surface Patterning of Mesoporous Niobium Oxide Films for Solar Energy Conversion

Abstract

An array of periodic surface features were patterned on mesoporous niobium oxide films by a soft-lithographic technique with the goal of constructing a photonic crystal (PC) structure on the back side of the oxide. The oxide films, fabricated by mixing sol-gel derived niobium oxide nanoparticles and hydroxypropyl cellulose, were employed as photoelectrodes in dye-sensitized solar cells (DSSCs), and their performance evaluated against their flat counterparts. The surface patterns were imprinted using a photocurable perfluoropolyether (PFPE) soft-replica of a silicon master with a two-dimensional array of cylindrical posts (200 nm (D) × 200 nm (H)) in hexagonal geometry. The PC on the niobium oxide surface caused large changes in optical measurements, particularly in the blue wavelengths. To evaluate the optical effect on solar energy conversion, the incident photon-to-current conversion efficiency (IPCE) was measured in the patterned devices and the control group. The IPCE of patterned niobium oxide anodes exhibited a relative enhancement in photocurrent generation over the wavelength range corresponding to the higher absorption in optical measurements.

Temperature-dependent surface porosity of Nb2O5 under high-flux, low-energy He+ ion irradiation

“…Over the past several years niobium (Nb) oxide micro-and nano-structures, particularly Nb 2 O 5 structures, have been studied and tested for a wide range of applications including solar energy conversion [1][2][3], chemical catalysts [4,5], supercapacitors [6], and bioapplications [7,8]. While this is certainly a wide range of applications, every study placed a common emphasis on enhancing Nb 2 O 5 surface area in a controlled manner.…”

Study of the Nb2O5 Insertion in ZnO to Dye-sensitized Solar Cells

“…In an attempt to improve electric conduction and minimize the dark current, several materials have been explored for this purpose, such as Al 2 O 3 , Nb 2 O 5 , ZrO 2 , SnO 2, In 2 O 3 and CeO 2 9,10 . In photovoltaic devices the Nb 2 O 5 forms an energy barrier due to its energy gap being larger when compared to other semiconductors, causing the increase of the open circuit potential, thus suggesting the reduction in the speed of the reactions of charge recombination 11,12,13 . For that reason Nb 2 O 5 layers have also been used as blocking layers of other oxides, preventing electron back-transfer 14 .…”

One‐Step Plasma Synthesis of Nb2O5 Nanofibers and their Enhanced Photocatalytic activity

“…Niobium (Nb) pentaoxide (Nb 2 O 5 ) is popular semiconductor because of its stability and various applications: gas sensor, [1] solar energy conversion, [2,3] lithium ion battery, [4] catalysts, [5] and photocatalysts. [6,7] Concerning photocatalysis application, after the discovery of hydrogen (H 2 ) production from water splitting using titanium oxide (TiO 2 ) by Honda and Fujishima, [8] development of highly effective photocatalysts has been extensively explored.…”

“…[14,15] Enhanced photocatalytic performances were identified on various nanosized Nb 2 O 5 materials including C, N co-modified niobium pentoxide nanoneedles [16] and core-shell nanocomposites. [17] Because highly porous materials are thought to enhance the activity of photocatalysis, [2,18] many works have been reported about fabrication of mesoporous Nb 2 O 5 nanostructures via such as sol-gel process, [19] electrospinning, [15] evaporation induced self-assembly method, [11,13] and solvothermal reaction. [6] Recently, Novakowski et al reported that helium (He) ion beam can be used for one-step fabrication of Nb 2 O 5 nanostructures, [3] nanometer sized protrusion were formed on the surface by He ion irradiation.…”