Flexible electronics

Flexible devices can be made from doped PANI and can be directly deposited by inkjet printing on a plastic sheet, such as PI. The functional material shows a crystalline ordering (35). 

The printing inks can be S5mthesized using a water-based process, thus toxic and mutagenic substances are avoided, which are commonly used in the production of PANI. These so printed devices show a very high negative supercapacitance measirred of -2.3 mF at 30 Hz that corresponds to a specific mass capacity of -799 Fg.  

The techniques of low temperature sintering of inkjet-printed metal precursor materials have been reviewed. In particular, the roU-to-roU processing has been described. Inkjet printing can be used as a highly reproducible noncontact patterning technique. In addition, it requires only small amoimts of functional materials (36). 

The fabricated materials can be used as interconnects and contacts for microelectronic apphcations, including organic light-emitting 

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Sazonov, A. Striakhilev, D. Lee, C.-H. Nathan, A. 2005. Low-temperature materials and thin-film transistors for flexible electronics. Proc. IEEE 93 1420-1428. 

MacDonald, B. 2007. Developments in polyester film for flexible electronics. 2007 Flexible Displays and Microelectronics Conference (Phoenix, AZ Feb. 5-8, 2007), p. 15.1. 

Cairns, D. K. Crawford, G. P. 2005. Electromechanical properties of transparent conducting substrates for flexible electronic displays. Proc. IEEE. 93 1451-1458. 

NW-TFT device performance does not change significantly upon slightly flexing the plastic substrate (Fig. 11.14d).67 The use of free-standing nanostructures for flexible electronics has also been demonstrated by various groups using nanotubes,68 nanowires,63 and nano- or micro-ribbons.69,70... 

INORGANIC SINGLE-CRYSTALLINE SEMICONDUCTOR MATERIALS FOR FLEXIBLE ELECTRONICS... 

Figure 14.10. Examples of flexible electronic paper are shown with a Polymer Vision flexible map on the left and an E-Ink-based Sony Digital Book on the right. 

When highly fluorescent ionic fluorophores, such as acridinium or xanthene dyes, are linked to a flexible electron-donor-substituted aryl group, a low-lying intramolecu-... 

G. Eda, G. Fanchini, M. Chhowalla, Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material, Nature Nanotechnology, 3 (2 0 08) 270-274. 

Laskarakis A, Logothetidis S, Kassavetis S et al (2007) Surface modification of poly(ethylene terephthalate) polymeric films for flexible electronics applications. Thin solid films 516 1443-1448... 

The use of UV-polymerized, vacuum-deposifed film has enabled fhe development of mulhlayer barrier coatings for thin-film phofovolfaics and flexible electronics. The patented system uses thin polymer layers that are deposited alternatively with thin barrier layers. The mulhlayer structure is composed from organic (polymer) and inorganic (oxide) layers. 

In addition to the thin-film solar cells, this system is suitable for use in other flexible electronics, such as a flexible, transparent, and light-weight encapsulation of organic light-emitting diode (OLED) displays and lighting. 

A complete stereocontrol is achieved by addition of the bulky silyl radical (Me3Si)3Si to a chiral and conformationally flexible electron-deficient olefin 163, as shown in equation 68213. Replacement of (Me3Si)3Si with a less sterically hindered (n-Bu)3Sn gives a mixture of syn and anti diastereomeric adducts 164 and 165 in a ratio of 7 3. The A values (kcalmol-1) of the tin, carbon and silicon species follow the order (n-Bu Sn (1.1) < Me (1.7) < Me3Si (2.5), and the bond length for C—Sn (2.2 A) is longer than that for C-Si (1.85 A)214 215. 

Fig. 7.2. Cl ass transition of film substrates of interest for applications in flexible electronics.

It is interesting to contrast these films with the other films being considered for flexible electronics especially for the higher performance flexible display market. The main candidates are shown in Fig. 7.2 which lists the substrates on the basis of increasing glass transition temperature (Tg) [5, 6],... 

Fig. 7.3. Upper processing temperature of film substrates of interest for flexible electronics applications.

The main properties of heat-stabilized PET and PEN relevant to flexible electronics are summarized in Fig. 7.9. Unstabilized PET and PEN films have the same set of... 

These properties have been discussed in the text and elsewhere [5, 6], This table shows that both heat-stabilized PET (e.g. Melinex ST504) and heat stabilized PEN (TeonexQ65A) have an excellent balance of the key properties required for flexible electronics. TeonexQ65A has a higher-temperature performance than Melinex (Fig. 7.9) and as a result of this set of properties TeonexQ65A is emerging as a leading material for the base substrate of OLED displays and active matrix backplanes. 

Fig. 7.13. Property requirements for different flexible electronics applications.

Alternatives to conventional photolithography will enable both reduction in cost and complexity for large-area electronics fabrication and will also help enable a transition from rigid substrates to flexible platforms. The transition towards roll-to-roll processing of flexible electronics may be required to follow the roadmap for low-cost large-area electronics. 

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