Electrochromic performance of sol-gel deposited WO3–V2O5 films

Özer, Nilgün; Lampert, Carl M.

doi:10.1016/s0040-6090(99)00144-3

Cited by 112 publications

(66 citation statements)

References 10 publications

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“…[ 23 ] X-ray diffraction (XRD) studies did not show any characteristic peaks that could be assigned to any crystalline or polycrystalline structure of V 2 O 5 . In agreement with previous reports, [ 24 ] we can therefore assume that our sol-gel V 2 O 5 layers are amorphous. This is the prerequisite for the extreme smoothness of the layers verifi ed by the AFM studies.…”

supporting

confidence: 92%

Solution Processed Vanadium Pentoxide as Charge Extraction Layer for Organic Solar Cells

Zilberberg

Trost

Schmidt

et al. 2011

Advanced Energy Materials

246

234

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Organic solar cells (OSCs) based on polymers and small molecules have seen a tremendous increase in interest during the past few years. Signifi cant progress in this fi eld seeded the prospect for a cost-effective and easy-to-fabricate photovoltaic technology-typical advantages claimed for organic (opto-)electronic devices. Very recently, certifi ed cell effi ciencies in excess of 7% have been reported for polymer based cells. [ 1 ] For large-scale and high-throughput production of OSCs, liquid processing of the functional layers is desirable. Aside from the active organic layers, inter-layers are typically required to facilitate the extraction of the photo-generated charges. Specifi cally, on the anode side, polyethylene dioxythiophene:polystyrenesulfonate (PEDOT:PSS) is regularly used. [ 2 ] However, PEDOT:PSS is burdened with structural and electrical inhomogeneity [ 3,4 ] and has been demonstrated to be an origin of limited device lifetime. [ 5 ] Particularly, the aqueous PEDOT:PSS dispersion and the acidic nature can cause substantial degradation. [6,7 ] Very recently, transition metal-oxides (TMOs) such as molybdenum-, vanadium-, or tungsten-oxide (MoO 3 , V 2 O 5 , and WO 3 ) with high work functions (WFs) of up to 6.9 eV have been shown to be promising alternatives to PEDOT:PSS. [8][9][10][11] TMOs have also been used as constituents of the connecting architecture in stacked organic light-emitting diodes and organic tandem solar cells. [12][13][14][15] The unique energetics of these TMOs has so far been predominantly accessible for fi lms thermally evaporated in high-vacuum.The fi rst results for TMO layers obtained by solution processing from nano-particle (NP) dispersions have been reported only very recently. [ 16,17 ] Meyer et al. prepared MoO 3 layers by dispersing MoO 3 NPs using a polymer as dispersing agent. After deposition, the layers had to be treated by an oxygen plasma to remove the polymer. A high WF of the resulting layers of 5.7-6 eV was obtained. A substantial drawback of the approach, however, is the observation of larger NP aggregates with a size of 100 nm and an overall high roughness of 25 nm (rms). Owing to their roughness these NP-layers are critical sources of shorts, especially over a large device area.In contrast, TMO layers (WO 3 , V 2 O 5 and MoO 3 ) have been prepared by sol-gel deposition, predominantly for electrochromic, catalytic and sensing applications. [18][19][20][21] Post processing of the sol-gel TMO layers at high temperatures (300 ° C-600 ° C) is routinely applied in order to achieve specifi c microstructures or crystalline phases in the materials, as required by the particular application. These high processing temperatures are not compatible with the temperature-sensitive substrates (e.g. poly mer foils) envisaged for low-cost, high-throughput fabrication of organic solar cells. In spite of this limitation, Steirer et al. have very recently used NiO prepared via a sol-gel route as a replacement for PEDOT:PSS in an organic solar cell. [ 22 ] The requirement of pos...

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supporting

confidence: 92%

Solution Processed Vanadium Pentoxide as Charge Extraction Layer for Organic Solar Cells

Zilberberg

Trost

Schmidt

et al. 2011

Advanced Energy Materials

246

234

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“…Among a broad range of mixed elements (Ni, Cr, Ti, Nb, etc. ), films containing less than 20% V were presented as being most promising for its color neutrality in its reduced state; similar results are reported in literature [7][8][9]. Some results pertaining to Sn, Zr, Li, Mo, and TiO 2 -doped Nb 2 O 5 were reported [10][11][12].…”

Section: Introductionsupporting

confidence: 79%

Electrochromism in composite WO3–Nb2O5 thin films synthesized by spray pyrolysis technique

et al. 2010

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Composite WO 3 -Nb 2 O 5 thin films were deposited on the glass and fluorine-doped tin oxide (FTO)-coated glass substrates using simple and inexpensive spray pyrolysis technique. The process parameters, like nozzleto-substrate distance, spray rate, concentration of sprayed solution, etc., were optimized to good quality films. The films were characterized for the structural, morphological, optical, and electrochromic properties. Structural and morphological characterizations of the films were carried out using scanning electron microscopy and X-ray diffraction techniques. Electrochemical properties of the Composite WO 3 -Nb2O 5 thin films were further studied using cyclicvoltammetry, chronoamperometry, chronocoulometry, and electrochemical Impedance spectroscopy.

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“…spin coater. To obtain homogenous and quite uniform thin films, the xerogel, once obtained, has been diluted with bidistilled water, and this solution has been spin-coated on indium tin oxide (ITO)-glass substrate (sheet resistivity ρ s =20 Ω/ρ, Unaxis GmbH) previously ultrasonically cleaned in acetone, bidistilled water and isopropanol and then dried with warm air (50°C) [17,18]. Different spinning rates have been used to obtain homogeneous films: here shown are the results regarding the films obtained at 2,400 rpm, spinning time 25 s, and ramp time (time employed to go from 0 to 2,400 rpm and back from 2,400 to 0 rpm) of 4 s. The thermal treatments for some of the films have been carried out in oven for 1 h, in air, at the following different temperatures: 100, 300, and 600°C.…”

Section: Methodsmentioning

confidence: 99%

Evolution from vanadium pentoxide xerogel to sodium-containing vanadates in thin films on ITO-coated glasses

Castriota

Epervrier

Barone

et al. 2007

Ionics

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In this work, the mechanism of the "gelation" process and the thermal-induced structural modifications of thin film of vanadium pentoxide xerogels deposited on indium tin oxide (ITO)-coated glasses have been studied. Vanadium pentoxide xerogel has been prepared by using the sol-gel proton exchange resin route without any resin pretreatment. To monitor the effect of the "resin efficiency" on the gelation process, the solution coming out from the resin has been collected in a sequence of different containers (vials), separately investigated by Raman spectroscopy. After the spin coating deposition, the thin films of vanadium pentoxide gel have been subjected to different annealing treatments. The highest thermal treatment (600°C) induces a complete transformation of the gel phase into an anhydrous polycrystalline phase of a sodiumcontaining vanadate, different from the usual V 2 O 5 crystal. It is due to the diffusion of foreign ions (mainly sodium) coming from the substrate into the vanadium oxide layer.

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Electrochromic performance of sol-gel deposited WO3–V2O5 films

Cited by 112 publications

References 10 publications

Solution Processed Vanadium Pentoxide as Charge Extraction Layer for Organic Solar Cells

Solution Processed Vanadium Pentoxide as Charge Extraction Layer for Organic Solar Cells

Electrochromism in composite WO3–Nb2O5 thin films synthesized by spray pyrolysis technique

Evolution from vanadium pentoxide xerogel to sodium-containing vanadates in thin films on ITO-coated glasses

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