Photovoltaic devices applications

Beaujuge PM, Subbiah J, Choudhury KR, Ellinger S, McCarley TD, So F, Reynolds JR (2010) Green dioxythiophene-benzothiadiazole donor-acceptor copolymers for photovoltaic device applications. Chem Mater 22 2093... 

In low-dimensional systems, such as quantum-confined. semiconductors and conjugated polymers, the first step of optical absorption is the creation of bound electron-hole pairs, known as excitons [34). Charge photogcncration (CPG) occurs when excitons break into positive and negative carriers. This process is of essential importance both for the understanding of the fundamental physics of these materials and for applications in photovoltaic devices and photodctcctors. Since exciton dissociation can be affected by an external electric field, field-induced spectroscopy is a powerful tool for studying CPG. 

Single-Crystal Silicon. Silicon is still the dominant material in photovoltaic. It has good efficiency, which is 25% in theory and 15% in actual practice. Silicon photovoltaic devices are made from wafers sliced from single crystal silicon ingots, produced in part by CVD (see Ch. 8, Sec. 5.1). However, silicon wafers are still costly, their size is limited, and they cannot be sliced to thicknesses less than 150 im. One crystalline silicon wafer yields only one solar cell, which has an output of only one watt. This means that such cells will always be expensive and can only be used where their high efficiency is essential and cost is not a major factor such as in a spacecraft applications. 

Originally photovoltaic devices were restricted to space applications, due to their high cost. In the last few years, cost has been reduced by more than an order of magnitude and the spectrum of applications is now much broader. 

Metal chalcogenide semi-conducting materials have found many applications in opto-electronic, solar cell and photovoltaic devices. Deposition of these materials can be achieved by a variety of techniques of which one of the most... 

Seager, C.H., and Ginley, D.S., (1982). Fundamental Studies of Grain Boundary Passivation in Polycrystalline Silicon with Application to Improved Photovoltaic Devices, Sandia Report, SAND82-1701, p. 19-21. 

Esterification constitutes a valuable alternative to the amidation strategy. As with amidation, the formation of the ester bond is performed following a first reaction step with acyl chloride. The ester bond has been extensively utilized to attach many organic and inorganic moieties. Porphyrins are a classic example of substrates covalently bound via esterification strategies their photoinduced electron transfer to the nanotube has been studied for applications in molecular electronics and photovoltaic devices (Fig. 3.6) [21]. 

Polythiophenes (PTs)/CNTs composites have emerged as an intriguing system for use as photovoltaic devices and field effect transistors [57]. Swager and Bao independently reported methods for the assembling of PTs/CNTs systems and showed their great potential as transparent conductive films [58]. Another interesting application arises from the possibility to functionalize the polythiophene backbone for applications as chemical sensors [134]. 

The reaction of solid porphyrin films with light in the presence of oxygen by producing MgTPP must affect electrical properties, in particular semi conduct on, photoconduction, and photovoltaic properties. We have provided evidence for "photodoping" by light and oxygen, a phenomenon that must be clearly understood if these materials are to have device applications. 

Films—Films have been formed from CNTs that are high strength, conductive, and transparent. They are being investigated for use in LCDs, photovoltaic devices, flexible displays (foldable TV screens) and touch screens, and are intended to replace indium tin oxide (ITO) in many applications. 

The application of Langmuir-Blodgett films as rectifiers and/or switches have been also proposed. Peterson [106] investigated two semiconductors polyparaphenylene 178 and polyphenylenevinylene 179 with these purposes in mind. These systems with the chain lengths of at least 20 units could also be used as photovoltaic devices since their electroluminescence should be readily detectable. The doping of such materials may be necessary but at present it is not clear whether they will form Langmuir-Blodgett films when doped. 

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