Showing papers on "Indium tin oxide published in 2006"

New Architecture for High-Efficiency Polymer Photovoltaic Cells Using Solution-Based Titanium Oxide as an Optical Spacer

Abstract: reported under AM1.5 (AM: air mass) illumination, this efficiency is not sufficient to meet realistic specifications for commercialization. The need to improve the light-to-electricity conversion efficiency requires the implementation of new materials and the exploration of new device architectures. Polymer-based photovoltaic cells are thin-film devices fabricated in the metal-insulator-metal configuration sketched in Figure 1a. The absorbing and charge-separating bulk-heterojunction layer with a thickness of approximately 100 nm is sandwiched between two charge-selective electrodes; a transparent bilayer electrode comprising poly(3,4-ethylenedioxylenethiophene):polystyrene sulfonic acid (PEDOT:PSS) on indium tin oxide (ITO) glass for collecting the holes and a lower-work-function metal (here, Al) for collecting the electrons. The work-function difference between the two electrodes provides a built-in potential that breaks the symmetry, thereby providing a driving force for the photogenerated electrons and holes toward their respective electrodes. Because of optical interference between the incident (from the ITO side) and back-reflected light, the intensity of the light is zero at the metallic (Al) electrode; Figure 1a shows a schematic representation of the spatial distribution of the squared optical electric-field strength. [9–11] Thus, a relatively large fraction of the active layer is in a dead-zone in which the photogeneration of carriers is significantly reduced. Moreover, this effect causes more electron–hole pairs to be produced near the ITO/PEDOT:PSS electrode, a distribution which is known to reduce the photovoltaic conversion efficiency. [12,13] This “optical interference effect” is especially important for thin-film structures where layer thicknesses are comparable to the absorption depth and the wavelength of the incident light, as is the case for photovoltaic cells fabricated from semiconducting polymers. In order to overcome these problems, one might simply increase the thickness of the active layer to absorb more light. Because of the low mobility of the charge carriers in the polymer:C60 composites, however, the increased internal resistance of thicker films will inevitably lead to a reduced fill factor. An alternative approach is to change the device architecture with the goal of spatially redistributing the light intensity inside the device by introducing an optical spacer between the active layer and the Al electrode as sketched in Figure 1a. [11] Although this revised architecture would appear to solve the problem, the prerequisites for an ideal optical spacer limit the choice of materials: the layer must be a good acceptor and an electron-transport material with a conduction band edge lower in energy than that of the lowest unoccupied molecular orbital (LUMO) of C60; the LUMO must be above (or close to) the Fermi energy of the collecting metal electrode; and it must be transparent to light with wavelengths within the solar spectrum.

Transition metal oxides as the buffer layer for polymer photovoltaic cells

Abstract: Polymer-based photovoltaic cells have been fabricated by inserting a thin, transparent, transition metal oxide layer between the transparent anode (indium tin oxide) and the polymer layer. Two different transition metal oxides, namely vanadium oxide and molybdenum oxide, were used and the device performance was compared. The surface of the oxide films and the interface between the polymer and the oxide was studied with the help of atomic force microscopy. The effect of the thickness of the oxide layer on electrical characteristics of the device was also studied and optimized thickness was achieved to give high power conversion efficiency of 3.3% under simulated AM1.5G illumination of 100mW∕cm2.

The Origin of the High Conductivity of Poly(3,4-ethylenedioxythiophene)−Poly(styrenesulfonate) (PEDOT−PSS) Plastic Electrodes

Abstract: The development of printed and flexible (opto)electronics requires specific materials for the device's electrodes Those materials must satisfy a combination of properties They must be electrically conducting, transparent, printable, and flexible The conducting polymer poly(3,4-ethylenedioxythiophene)− poly(styrenesulfonate) (PEDOT−PSS) is known as a promising candidate Its conductivity can be increased by 3 orders of magnitude by the secondary dopant diethylene glycol (DEG) This “secondary doping” phenomenon is clarified in a combined photoelectron spectroscopy and scanning probe microscopy investigation PEDOT−PSS appears to form a three-dimensional conducting network explaining the improvement of its electrical property upon addition of DEG Polymer light emitting diodes are successfully fabricated using the transparent plastic PEDOT−PSS electrodes instead of the traditionally used indium tin oxide

Inverted bulk-heterojunction organic photovoltaic device using a solution-derived ZnO underlayer

Abstract: Inverted organic photovoltaic devices based on a blend of poly(3-hexylthiophene) and a fullerene have been developed by inserting a solution-processed ZnO interlayer between the indium tin oxide (ITO) electrode and the active layer using Ag as a hole-collecting back contact. Efficient electron extraction through the ZnO and hole extraction through the Ag, with minimal loss in open-circuit potential, is observed with a certified power conversion efficiency of 2.58%. The inverted architecture removes the need for the use of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) as an ITO modifier and for the use of a low-work-function metal as the back contact in the device.

Efficient inverted polymer solar cells

Abstract: We investigate the effect of interfacial buffer layers—vanadium oxide (V2O5) and cesium carbonate (Cs2CO3)—on the performance of polymer solar cells based on regioregular poly-(3-hexylthiophene) and [6,6]-phenyl C60 butyric acid methyl ester blend. The polarity of solar cells can be controlled by the relative positions of these two interfacial layers. Efficient inverted polymer solar cells were fabricated with the structure of indium tin oxide (ITO)/Cs2CO3/polymer blend/vanadium oxide (V2O5)/aluminum (Al). Short-circuit current of 8.42mA∕cm2, open-circuit voltage of 0.56V, and power conversion efficiency of 2.25% under a AM1.5G 130mW∕cm2 condition were achieved. The interfacial layers were also used to fabricate polymer solar cells using ITO and a thin gold (Au) layer as the transparent electrodes. The thickness of V2O5 layer (10nm) makes it an effective protective layer for the active layer so that ITO can be used for both the electrodes, enabling highly efficient transparent polymer solar cells (i.e., p...

Highly efficient inverted organic photovoltaics using solution based titanium oxide as electron selective contact

Abstract: The challenge to reversing the layer sequence of organic photovoltaics (OPVs) is to prepare a selective contact bottom cathode and to achieve a suitable morphology for carrier collection in the inverted structure. The authors report the creation of an efficient electron selective bottom contact based on a solution-processed titanium oxide interfacial layer on the top of indium tin oxide. The use of o-xylene as a solvent creates an efficient carrier collection network with little vertical phase segregation, providing sufficient performance for both regular and inverted solar cells. The authors demonstrate inverted layer sequence OPVs with AM 1.5 calibrated power conversion efficiencies of over 3%.

A method of printing carbon nanotube thin films

Abstract: This paper describes a fabrication method for carbon nanotube thin films on various substrates including PET (polyethylene terephthalate), glass, polymethyl-methacrylate (PMMA), and silicon. The method combines a polydimethysiloxane (PDMS) based transfer-printing technique with vacuum filtration, and allows controlled deposition—and patterning if needed—of large area highly conducting carbon nanotube films with high homogeneity. In the visible and infrared range, the performance characteristics of fabricated films are comparable to that of indium tin oxide (ITO) on flexible substrates.

Thin films engineering of indium tin oxide: large area flat panel displays application

Abstract: Indium Tin Oxide (ITO) thin films with a variety of microstructures were deposited using a large area conventional DC magnetron sputtering system for flat panel displays manufacturing. Highly uniform ITO films with an average thickness of ∼100 ± 3 nm on the ∼0.6 m2 substrate area were obtained. Film structures with small amounts of crystalline sites were produced by room temperature deposition, and an entirely amorphous structure with excellent etching properties was achieved through optimized incorporation of hydrogen in the film, providing a significant increase in the crystallization temperature of ITO. Post-annealing of such a sample yielded a randomly orientated polycrystalline structure with superior conductivity and transparency. The polycrystalline ITO films, produced at the sputtering substrate temperature of 200 °C, provided structures with preferential grain orientation in both and directions, controlled by the amount of oxygen and increased process pressure. The impact of oxygen and pressure with related structures on the macroscopic properties of the layers was studied. Morphological features of the films such as phase/grain structure and surface roughness were investigated using SEM and AFM. Layers with an equiaxed grain structure of about 30 nm crystal size revealed an ultra smooth surface with RMS values of about 1 nm. Specific resistivities as low as 150 μΩ cm and transmittance values above 92% at 550 nm wavelength were obtained for polycrystalline layers with preferential grain orientation.

Towards See-Through Displays: Fully Transparent Thin-Film Transistors Driving Transparent Organic Light-Emitting Diodes**

Abstract: Fully transparent computer displays have, until now, been the vision of science-fiction movies. Nevertheless, there are numerous applications for these devices ranging, for example, from head-mounted displays to their integration in automotive windshields. In this paper we demonstrate that this vision is on the verge of becoming reality. The realization of entirely transparent displays requires both transparent light-emitting devices, in our case organic light-emitting diodes (OLEDs) with transparent contacts, and a driving scheme based on transparent thin-film transistors (TTFTs). Since the early reports on electroluminescence from multilayer, thin-film devices composed of vacuum-sublimed small organic molecules [1] and spin-coated conjugated polymers, [2] substantial research has been devoted to the improvement of device efficiencies, color purity, and lifetime. Incitement of this development is the potential use of OLEDs in future commercial flat-panel displays. OLEDs usually consist of a layer sequence of organic functional materials (charge transporters/blockers/emitters) with an overall thickness of the order of 100 nm. Most of these materials absorb light in the deep-blue or ultraviolet spectral region and are nearly transparent in the visible part of the spectrum. Organic layers applied to emit visible light are often based on so-called guest–host systems, in which a wide-bandgap host material (absorbing in the UVonly) is doped with a few weight percent of a light-emitting dye. [3] As a result, the emitting layer appears transparent. Transparent conductive oxides, most prominently indium tin oxide (ITO) and aluminum-doped ZnO (AZO), may be used as electrical contacts to OLEDs. Therefore, OLEDs seem to be promising devices for the realization of entirely transparent visible-light emitters. [4–6] OLED displays driven in passive-matrix mode are based on conventional bottom-emitting OLEDs and are considered as an approach to fabricate small-sized, low-information-content displays with moderate pixel counts. To accomplish largerarea, high-resolution OLED displays an active-matrix-addressing scheme has been suggested. [7] Conventional a-Si:H or poly-Si TFT backplanes are not suitable as drivers for transparent displays because they are opaque in the visible part of the spectrum. Putting pixels and transistors next to each other would compromise the displays’ fill factor. Organic field-effect transistors (OFETs) as pixel drivers for OLEDs have been discussed by Sirringhaus et al. [8] Transparent OFETs have also been reported. [9] However, their performance is still poor; transparent active pixels using OFETs have not yet been demonstrated. Therefore, in this paper we focus on the production of TTFTs based on the wide-bandgap oxide semiconductor zinc tin oxide (ZnO)x(SnO2)1–x ,a s a viable alternative to previously fabricated devices. Recently, research on TTFTs with channels made from ox

Green fluorescent organic light-emitting device with external quantum efficiency of nearly 10%

Abstract: Green fluorescent organic light-emitting device (OLED) exhibiting a high external quantum efficiency of nearly 10% has been developed. The OLED consists of simple three organic layers, using NPB, 0.8% C545T doped TPBA, and DBzA as a hole-transporting layer, an emitting layer, and an electron-transporting layer, respectively, [fluorocarbon coated indium tin oxide/NPB (60 nm)/08% C545T doped TPBA (40 nm)/DBzA (20 nm)/LiF (1 nm/Al], where NPB is 4,4′-bis (N-phenyl-1-naphthylamino)biphenyl, C545T is 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo[l]pyrano[6 7 8-ij]quinolizin-11-one, TPBA is 9,9′,10,10′-tetraphenyl-2,2′-bianthracene, and DBzA is 9,10-bis[4-(6-methylbenzothiazol-2-yl)phenyl]anthracene. The high external quantum efficiency is maintained in the wide range of current density of 2–100 mA∕cm2. The current efficiency and power efficiency of the OLED are also very high, 29.8 cd/A and 26.2 lm/W, respectively, at a current density of 20 mA/cm2. The OLED is promising for prac...

Using Self‐Assembling Dipole Molecules to Improve Charge Collection in Molecular Solar Cells

Abstract: Surface modification of indium tin oxide (ITO)-coated substrates through the use of self-assembled monolayers (SAMs) of molecules with permanent dipole moments has been used to control the anode work function and device performance in molecular solar cells based on a CuPc:C60 (CuPc: copper phthalocyanine) heterojunction. Use of SAMs increases both the short-circuit current density (Jsc) and fill factor, increasing the power-conversion efficiency by up to an order of magnitude. This improvement is attributed primarily to an enhanced interfacial charge transfer rate at the anode, due to both a decrease in the interfacial energy step between the anode work function and the highest occupied molecular orbital (HOMO) level of the organic layer, and a better compatibility of the SAM-modified electrodes with the initial CuPc layers, which leads to a higher density of active sites for charge transfer. An additional factor may be the influence of increasing electric field at the heterojunction on the exciton-dissociation efficiency. This is supported by calculations of the electric potential distribution for the structures. Work-function modification has virtually no effect on the open-circuit voltage (Voc), in accordance with the idea that Voc is controlled primarily by the energy levels of the donor and acceptor materials.

Carbon nanotube sheets as electrodes in organic light-emitting diodes.

Abstract: High performance organic light-emitting diodes (OLEDs) were implemented on transparent and conductive single-wall carbon nanotube sheets. At the maximum achieved brightness of 2800cdm−2 the luminance efficiency of our carbon nanotube-based OLED is 1.4cdA−1 which is comparable to the 1.9cdA−1 measured for an optimized indium tin oxide anode device made under the same experimental conditions. A thin parylene buffer layer between the carbon nanotube anode and the hole transport layer is required in order to readily achieve the measured performance.

Transparent conductive Al-doped ZnO films for liquid crystal displays

Abstract: Al-doped zinc oxide (ZnO:Al) films were applied to liquid crystal displays (LCDs) as transparent electrodes substituting indium tin oxide (ITO). While the ZnO:Al-based twisted nematic LCD cell showed similar operational behavior to ITO-based counterpart, its electro-optical (EO) and residual dc (r‐dc) characteristics were somewhat improved. Capacitance-voltage relations suggested that these improved EO and r‐dc characteristics of the ZnO:Al-based LCD cell are due to the substantially lower density of charge carrier trapping centers in the polyimide layer∕electrode interface region, demonstrating high application potential of ZnO:Al films as transparent electrodes of LCDs.

Highly Efficient Electroluminescence from Green‐Light‐Emitting Electrochemical Cells Based on CuI Complexes

Abstract: The complexes [Cu(dnpb)(DPEphos)](+)(X-) (dnpb and DPEphos are 2,9-di-n-butyl-1,10-phenanthroline and bis[2-(diphenyl-phosphino)phenyl]ether, respectively, and X- is BF4-, ClO4-, or PF6-) can form high quality films with photoluminescence quantum yields of up to 71 +/- 7% Their electroluminescent properties are studied using the device-structure indium tin oxide (ITO)/complex/metal cathiode The devices emit green light efficiently, with an emission maximum of 523 nm, and work in the mode of light-emitting electrochemical cells The response time of the devices greatly depends on the driving voltage, the counterions, and the thickness of the complex film After pre-biasing at 25 V for 40 s, the devices turn on instantly, with a turn-on voltage of ca 29 V A current efficiency of 56 cd A(-1) and an external quantum efficiency of 16% are realised with Al as the cathode Using a low-work-function metal as the cathode can significantly enhance the brightness of the device almost without affecting the turn-on voltage and current efficiency With a Ca cathode, a brightness of 150 cd m(-2) at 6 V and 4100 cd m(-2) at 25 V is demonstrated The electroluminescent performance of these types of complexes is among the best so far for transition metal complexes with counterions

Highly Efficient Pure-White-Light-Emitting Diodes from a Single Polymer: Polyfluorene with Naphthalimide Moieties†

Abstract: Light-emitting diodes exhibiting efficient pure-white-light electroluminescence have been successfully developed by using a single polymer: polyfluorene derivatives with 1,8-naphthalimide chromophores chemically doped onto the polyfluorene backbones. By adjusting the emission wavelength of the 1,8-naphthalimide components and optimizing the relative content of 1,8-naphthalimide derivatives in the resulting polymers, white-light electroluminescence from a single polymer, as opposed to a polymer blend, has been obtained in a device with a configuration of indium tin oxide/poly(3,4-ethyleiledioxythiophene)(50 nm)/polymer(80 nm)/Ca(10 nm)/Al(100 nm). The device exhibits Commission Internationale de I'Eclairage coordinates of (0.32,0.36), a maximum brightness of 11900 cd m(-2), a current efficiency of 3.8 cd A(-1), a power efficiency of 2.0 lm W-1. an external quantum efficiency of 1.50 %, and quite stable color coordinates at different driving voltages, even at high luminances of over 5000 cd m(-2).

Hydrothermal synthesis of In2O3 for detecting H2S in air

Abstract: Nanocrystalline In 2 O 3 gas sensing material was prepared by sintering a precursor In(OH) 3 at 600 °C which was hydrothermally synthesized at 250 °C for 24 h by using InCl 3 ·4H 2 O as a starting material The nanopowder was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry–differential scanning calorimetry (TG–DSC) and X-ray photoelectron spectrometer (XPS) The results indicated that the precursor of indium oxide was cubic indium hydroxide with range size of 50–80 nm, and indium oxide was composed of In and O Gas sensing properties of the sensors were tested by mixing a gas in air at static state, the tested results showed that the sensor based on In 2 O 3 nanocrystals had satisfying H 2 S gas sensing properties at rather low temperature

Direct Electrodeposition of Gold Nanoparticles onto Indium Tin Oxide Film Coated Glass: Application to the Detection of Arsenic(III)

Abstract: Gold nanoparticle modified indium tin oxide (ITO) film coated glass electrodes were prepared for the first time through direct electrochemical deposition from 0.5 M H2SO4 containing 0.1 mM HAuCl4. The resulting electrode surfaces were characterized with AFM. Cyclic voltammetry and linear sweep voltammetry (LSV) of arsenic(III) on the modified electrodes were performed. After optimization, a LOD of 5 +/- 0.2 ppb was obtained with 60 s deposition at -0.6 V (vs. SCE) in 1 M HNO3 using LSV.

Nonaqueous synthesis of uniform indium tin oxide nanocrystals and their electrical conductivity in dependence of the tin oxide concentration

Abstract: Indium tin oxide nanoparticles with tin oxide contents varying from 2 to 30 wt % have been synthesized via a nonaqueous sol−gel procedure involving the solvothermal treatment of indium acetylacetonate and tin tert-butoxide in benzyl alcohol. According to powder X-ray diffraction analysis combined with Rietveld refinement all the materials are crystalline with the cubic bixbyite structure of indium oxide without any indication of SnO2 as an additional phase. Transmission electron microscopy studies proved that the nearly spherical particles are relatively uniform in size and shape with crystallite sizes in the range of 5−10 nm. X-ray photoelectron spectroscopy results showed that the final composition of the nanoparticles coincided well with the initial indium acetylacetonate-to-tin tert-butoxide ratio. Furthermore, a high amount of oxygen vacancies was detected, which contribute to the good electrical conductivity of the nanoparticles. Conductivity measurements on the as-synthesized nanopowders pressed in...

GaInN light-emitting diode with conductive omnidirectional reflector having a low-refractive-index indium-tin oxide layer

Abstract: Enhancement of light extraction in a GaInN light-emitting diode (LED) employing a conductive omnidirectional reflector (ODR) consisting of GaN, an indium-tin oxide (ITO) nanorod low-refractive-index layer, and an Ag layer is presented. An array of ITO nanorods is deposited on p-type GaN by oblique-angle electron-beam deposition. The refractive index of the nanorod ITO layer is 1.34 at 461nm, significantly lower than that of dense ITO layer, which is n=2.06. The GaInN LEDs with GaN∕low-n ITO/Ag ODR show a lower forward voltage and a 31.6% higher light-extraction efficiency than LEDs with Ag reflector. This is attributed to enhanced reflectivity of the ODR that employs the low-n ITO layer.

Electroluminescence from ZnO nanowire/polymer composite p-n junction

Abstract: The characteristics of a hybrid p-n junction consisting of the hole-conducting polymer poly(3,4-ethylene-dioxythiophene)-poly(styrene-sulfonate) (PEDOT/PSS) and n-ZnO nanorods grown on an n-GaN layer on sapphire are reported. Spin coating of polystyrene was used to electrically isolate neighboring nanorods and a top layer of transparent conducting indium tin oxide (ITO) was used to contact the PEDOT/PSS. Multiple peaks are observed in the electroluminescence spectrum from the structure under forward bias, including ZnO band edge emission at ∼383nm as well as peaks at 430, 640, and 748nm. The threshold bias for UV light emission was <3V, corresponding to a current density of 6.08Acm−2 through the PEDOT/PSS at 3V.

Adaptive liquid crystal lens with large focal length tunability.

Abstract: We demonstrate a tunable-focus lens using a spherical glass shell and a homogeneous liquid crystal (LC) cell. The inner surface of the glass shell and the bottom surface of the LC cell are coated with indium tin oxide (ITO) electrodes while the LC layer is sandwiched between the spherical and flat ITO electrodes. When a voltage is applied to the electrodes, a centro-symmetric gradient refractive index is generated within the LC layer and the focusing behavior occurs. Based on our analysis, the focal length tunability of the LC lens depends significantly on the filled material in the sag region. For the air-filled LC lens we designed, its focal length can be tuned from infinity to ~96 cm. A method for reducing the operating voltage is proposed.

Band gap shift in the indium-tin-oxide films on polyethylene napthalate after thermal annealing in air

Abstract: Indium-tin-oxide (ITO) thin films on polyethylene napthalate (PEN) with high carrier concentration (∼1021∕cm3) have been grown by electron-beam deposition without the introduction of oxygen into the chamber. The electrical properties of the ITO films (such as, carrier concentration, electrical mobility, and resistivity) abruptly changed after annealing in the air atmospheres. In addition, optical transmittance and optical band gap values significantly changed after heat treatment. The optical band gap narrowing behavior is observed in the as-deposited sample because of impurity band and heavy carrier concentration. The influence of annealing in air on the electrical and optical properties of ITO∕PEN samples can be explained by the change in the free electron concentration, which is evaluated in terms of the oxygen content. Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy analyses are used to determine the oxygen content in the film. Hall effect measurements are used to determine...

Metallic Photonic Crystals Based on Solution-Processible Gold Nanoparticles

Abstract: We demonstrate the fabrication of metallic photonic crystals, in the form of a periodic array of gold nanowires on a waveguide, by spin-coating a colloidal gold suspension onto a photoresist mask and subsequent annealing. The photoresist mask with a period below 500 nm is manufactured by interference lithography on an indium tin oxide (ITO) glass substrate, where the ITO layer has a thickness around 210 nm and acts as the waveguide. The width of the nanowires can be controlled from 100 to 300 nm by changing the duty cycle of the mask. During evaporation of solvent, the gold nanoparticles are drawn to the grooves of the grating with apparently complete dewetting off the photoresist for channels less than 2 μm in width, which therefore form nanowires after the annealing process. Strong coupling between the waveguide mode and the plasmon resonance of the nanowires, which is dependent on the polarization and incidence angle of the light wave, is demonstrated by optical extinction measurements. Continuity of t...

Semitransparent organic photovoltaic cells

Abstract: We demonstrate semitransparent, small molecular weight organic solar cells employing a thin silver/indium tin oxide compound cathode with a maximum transmission of (60±6)% averaged over the visible spectral range and with a power conversion efficiency, ηp=(0.28±0.03)% under simulated, AM1.5G, 1 sun illumination. By increasing the Ag thickness, an average transmission of (26±3)% is achieved with ηp=(0.62±0.06)%, a value approximately half of that obtained for the same structure employing a conventional, reflective, and thick Ag cathode. A semitransparent tandem organic solar cell with ηp=(0.48±0.02)% and an average transmission of (44±4)% is also demonstrated. Semitransparent organic photovoltaic cells have potential uses as tinted and power-generating thin-film coatings on architectural surfaces, such as windows and walls. The use of a transparent top electrode also significantly simplifies the design of tandem cells, relaxing requirements for the placement of different absorbing materials at the maxima o...

Organic Solar Cells Using Transparent SnO2–F Anodes

Abstract: Organic solar cells have attracted attention as a means to achieve low-cost solar-energy conversion owing to their ease of manufacture and compatibility with flexible substrates. Conventional organic molecular photovoltaic (PV) devices and light-emitting diodes (OLEDs) are typically grown on transparent indium tin oxide (ITO) anodes that are also widely used for flat-panel displays (FPDs). The scarcity of In, along with the rapid expansion of FPD production, has resulted in a soaring price of ITO-coated glass substrates, with the current price up to ten times greater than in 2003. Alternative transparent conducting oxides such as doped SnO2 or ZnO have been used as electrodes in dye-sensitized, CdTe, microcrystalline Si, and amorphous Si PV devices. Organic small-molecule or polymeric devices, with active layers typically < 1000 A thick, can readily be shorted owing to the pronounced surface-roughness characteristic of these oxide variants. Nevertheless, the cost of F-doped SnO2 (SnO2–F)coated glass is less than one third that of ITO-coated glass. While there have been reports of using SnO2–F as the transparent anode for polymeric OLEDs and solar cells, to our knowledge there has yet to be a demonstration of an organic heterojunction (HJ) PV cell based on SnO2–F anodes with an efficiency greater than 0.1 %. Here, we report on copper phthalocyanine (CuPc)/C60 HJ PV cells on SnO2–F anodes [8] with a power conversion efficiency of 2.5 % at 1 sun simulated AM 1.5 G (AM: air mass; G: Global) illumination. The organic layers were grown by organic vapor-phase deposition (OVPD) that enabled complete coverage of the rough oxide surface, effectively preventing shorts between opposing cathode and anode contacts. In addition, we show that by controlling the organic-film morphology, we can grow the donor–acceptor (D–A) interface into a three-dimensional interdigitated bulk HJ (BHJ) structure, resulting in power-conversion efficiencies nearly twice those of analogous devices with a planar heterointerface. As shown in Figure 1a, the 750 nm thick SnO2–F-coated glass substrates have 70–80 % transmittance in the visible range, or approximately 10 % less than that for glass with 150 nm thick ITO coatings. The absorption of both substrates has a high-energy cutoff at wavelengths less than 350 nm, implying a match of the transparency window to that of the solar radiation spectrum. The sheet resistance of SnO2–F-coated glass is less than 12 X/sq., lower than that of ITO-coated glass (15 X/sq.) The high transparency and small resistance C O M M U N IC A TI O N S

Atomic Layer Deposition of In2O3 Using Cyclopentadienyl Indium: A New Synthetic Route to Transparent Conducting Oxide Films

Abstract: Indium oxide (In2O3) forms the basis for an important class of transparent conducting oxides that see wide use in optoelectronic devices, flat-panel displays, and photovoltaics. Here we present a new method for depositing In2O3 thin films by atomic layer deposition (ALD) using alternating exposures to cyclopentadienyl indium and ozone. Using a precursor vaporization temperature of 40 °C and deposition temperatures of 200−450 °C, we measure growth rates of 1.3−2.0 A/cycle. A significant advantage of this synthesis route over previous techniques is the ability to conformally coat porous materials such as anodic aluminum oxide membranes. The deposited films are nanocrystalline, cubic phase In2O3 and are highly transparent and conducting. In situ quadrupole mass spectrometry and quartz crystal microbalance measurements elucidate the details of the In2O3 growth mechanism.