Transparent conductive electrode

An a-Si H-based position sensor consists of an intrinsic film sandwiched between two transparent conductive electrodes [637]. Two line contacts on the top are perpendicular to two on the bottom. When a light spot is incident on the device, carriers are generated, and a photocurrent flows to the contacts. The contacts form resistive dividers, so that from the ratio of the photocurrents the lateral position relative to the top or bottom contacts can be determined. The top contacts give the x-position, and the bottom contacts the y-position. 

X. Jiang, F.L. Wong, M.K. Fung, and S.T. Lee, Aluminum-doped zinc oxide films as transparent conductive electrode for organic light-emitting devices, Appl. Phys. Lett., 83 1875-1877, 2003. 

Li XS, Zhu YW, Cai WW, Borysiak M, Han BY, Chen D, Piner RD, Colombo L, Ruoff RS (2009) Transfer of large-area graphene films for high-performance transparent conductive electrodes. Nano Lett 9 4359... 

In this book the chemical, structural, optical, electrical, and interface properties of zinc oxide are summarized with special emphasis on the use of ZnO as transparent conductive electrode in thin film solar cells. This application has a number of requirements, which can be fulfilled by ZnO ... 

A PDLC shutter "sandwiches a film of the PDLC material between conducting substrates and utilizes no insulation or alignment layers. The substrates usually consist of either glass or plastic coated with a transparent conducting electrode such as a thin, vacuum deposited layer of indium tin oxide. The application of the transparent conducting electrode usually requires heating the substrate above 180°C, limiting the types of useable plastics. 

Tin (IV) oxide, Sn02, (rutile-type structure), a well-established n-type semiconductor with a wide band gap ( gap = 3.6 eV at 300 K) also has potential applications as a catalyst support,as transparent conducting electrodes,and as a gas sensor.i This material possesses many advantages, such as (i) high thermodynamic stability in air (at least up to 500 °C), (ii) low cost, and (iii) the possibility of the introduction of catalysts or dopants to enhance the sensitivity or selectivity. ... 

Critical properties of TCO coatings are electrical resistance and transparency [3], but for solar cell applications very often texture and large haze factors, i.e., ratio of diffuse to total transmission, have similar importance. Large haze factors have been shown to influence positively the efficiency of silicon solar cells, because the reflection at the TCO-silicon interface is reduced and the scattering increases the pathway of light inside the active material. The preparation and characteristics of several TCO materials have been reviewed by Chopra et al. [92] and Dawar and Joshi [93]. The optical and electrical properties of ITO and aluminum doped zinc oxide have been studied in detail by Granqvist and coworkers [94, 95], but these films were prepared by sputtering and not by CVD. Very recently they also published an overview of transparent conductive electrodes for electrochromic devices [7]. 

In order to utilize this effect for displays, one needs one or two transparent conductive electrodes consisting of, say, indium tin oxide. (Two in the active case and one in the passive case.) Required specifications are a transmittance of 80 to 90% and an area resistance less than 300 fin 1. Figure 41 shows the spectral transmittance of such electrode coatings. 

The development of transparent conductive electrodes based on SWNT thin films represented an outstanding scientific breakthrough for applications in the area of optoelectronics. However, to build integrated CNT-polymer-based systems it is necessary to engineer the interfaces between the two constituents through organized nanotube architectures. 

In principle, devices are constmcted as a series of thin films on glass. Transparent conducting electrodes, usually indium tin oxide (ITO), serve as electrodes, sandwiching a film of WO3, an ion-conducting electrolyte and a source/sink of metal ions (Eigure 9.9c). In practice, many designs have been explored. 

In addition to its hquid crystalline phase behavior, graphene has been demonstrated as a transparent electrode in LCD devices and a potential substitute for metal oxide electrodes [132]. It has been found that the electrooptical characteristics of such devices are superior in nature. In a similar fashion GO has been utilized in its reduced form in LC cells to study the field-induced reorientation of a nematic LC [133, 134]. These preliminary results are very encouraging for future LC devices. The advantages of graphene compared to conventionally used metal oxide electrodes in terms of low resistivity, high transparency and chemical stability hold great promise for large scale exploitation as transparent conductive electrodes. 

Figure 1. Schematic representation of a polymer dispersed liquid crystal (PDLC) sandwiched between transparent conducting electrodes. The upper pixel is the opaque OFF-state and the lower pixel is the transparent ON-state.

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