Bandgap tailored

Another material with similar property is GaAs in which the addition of aluminum atoms in the crystal lattice results in the increase in the bandgap with the formation of AlxGa(i x)As. Electrodeposition therefore provides a convenient platform for bandgap tailoring in some semiconductor materials and devices. 

The many possible combinations of II-V and II-VI compounds allow the tailoring of electronic and opto-electronic properties to suit specific applications. Of particular importance is the control of the stoichiometry of the element involved. This is achieved by the proper handling of the MOCVD reactions. Being able to tailor the bandgap imparts great flexibility in the design of transistors and optoelectronic devices. 

The m-V and II-VI semiconductor compounds have excellent optical properties and are the most important group of optoelectronic materials, which are all produced by CVD for many optoelectronic applications. The properties of these materials and their CVD reactions are reviewed in Ch. 12, Secs. 3.0 and 4.0 and Ch. 13, Sec. 6.0. It is possible to tailor the bandgap, by the proper combination of these materials, to suit any given application (See Fig. 13.2 of Ch. 13). 

Ballato, J., Tailorable visible photonic bandgaps through microstructural order and coupled material effects in SiOj colloidal crystals, J. Opt. Soc. Am. B, 17, 219, 2000. 

Germanium Photovoltaic devices, photodetectors, tailor bandgap on silicon. 

Only the semiconductor SWNT are suitable for the preparation of field-effect transistors (FET) so IBM researchers (Science, April 27. 2001) have developed a destructive technique for eliminating conducting tubes from conductor/semiconductor clumps with a current burst. The technique can also be used to remove the outer layers of multiwallcd tubes that consist of multiple concentric tubes about a common axis. Bandgaps increase as the diameter of multiwalled tubes is decreased which means that the destructive technique can be used to tailor a semiconductor tube to specific requirements. 

A lot of work has been devoted to the elaboration of more and more purposely tailored monomers, followed by electropolymerization, in order to improve a given property of the resulting polymer, e.g., a low bandgap. Approaches have also been made to synthesize oligomers, in order to prepare a better-defined polymer with improved properties. However, little work has been published outside the three main families, namely thiophene (especially EDOT), pyrrole, and aniline derivatives. In this section, we will only recall which kind of approach in monomer tailoring has been followed, and focus on some examples where the electrochemical behavior of the monomers has been found different from what could be expected. 

The performance of NC-polymer hybrid solar cells increased constantly as well during the past years, but PCE values are still by a factor of 2 lower than that for pure OPV. Here, hybrid solar cell technologies benefit from the development of low-bandgap polymers from OPV, leading to an increased utilization of the incident solar radiation [81, 19]. However, the development of suitable low-bandgap polymers has been optimized for their utilization with fullerene-based acceptors such as PCPM and its derivatives, and the tailored design of polymers for specific... 

It is easy to tailor their optical properties by modifying the polythiophenes (PTs) via simple substitution on the main chain, at least for bandgaps varying from 1 to 3 eV [31, 32], The chemical control of bandgaps is not easily achieved for the poly(/ -phenylenevinylene) (PPV) [33] or poly(p-phenylene) (PPP) [34] systems that represent two of the other processable polymer families. 

Agarwal V, del Rio JA (2003) Tailoring the photonic bandgap of a porous silicon dielectric mirror. Appl Phys Lett 82 1512-1514... 

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