Semiconductors in solar cells

If neither of these goals can be realized, layered semiconductors may not become useful electrode material in either semiconductor liquid junction or Schottky junction devices. Fortunately, evidence is already being obtained that the negative effects due to steps can be at least temporarily and partially alleviated (35, 36). Future development of chemical methods to inhibit deflection of minority carriers to the edges of steps and to reduce the high recombination rates at steps may open the way for the use of polycrystalline layered chalcogenide semiconductors in solar cell devices. 

Use Semiconductor in solar cells, thin-film transistors, infrared detectors, ultrasonic amplifiers. 

Titanium oxide, Ti02, is used as a white pigment in paint and paper, also as a semiconductor in solar cells. 

Semiconductor and Solar Cells. High purity (up to 99.9%) antimony has a limited but important appHcation in the manufacture of semiconductor devices (see Semiconductors). It may be obtained by reduction of a chemically purified antimony compound with a high purity gaseous or soHd reductant, or by thermal decomposition of stibine. The reduced metal may be further purified by pyrometaHurgical and zone melting techniques. 

The most common oxidation state of titanium is +4, in which the atom has lost both its 4s-electrons and its two 3d-electrons. Its most important compound is tita-nium(IV) oxide, Ti02, which is almost universally known as titanium dioxide. This oxide is a brilliantly white (when finely powdered), nontoxic, stable solid used as the white pigment in paints and paper. It acts as a semiconductor in the presence of light, and so it is used to convert solar radiation into electrical energy in solar cells. 

By 1927, another metal semiconductor junction solar-cell (In this case made of copper and the semiconductor copper oxide), had been... 

The majority of important semiconducting materials are isoelectronic with elemental silicon. Important semiconductor materials include the III-V (13-15) materials such as GaAs or InP, and II-VI (12-16) materials such as CdS or ZnSe (Table 1). These compound semiconductors are most often formed by combining elements displaced on either side of silicon by one place (i.e., Ill = Ga or In and V = N or As for a III-V material) or two places (i.e., II = Zn or Cd and VI = S or Se for a II-VI material) in the periodic table. Other materials are of specialist importance, especially ternary materials such as CuInE2 (E = S and Se), which find applications in solar cell technologies, as do materials of III-VI composition such as InxS, although their properties are often complicated by the potential for the formation of a wide range of similar phases. 

The different types of quinones active in photosynthesis are being used as electron acceptors in solar cells. The compounds such as Fd and NADP could also be used as electron/proton acceptors in the photoelectrochemical cells. Several researchers have attempted the same approach with a combination of two or more solid-state junctions or semiconductor-electrolyte junctions using bulk materials and powders. Here, the semiconductors can be chosen to carry out either oxygen- or hydrogen-evolving photocatalysis based on the semiconductor electronic band structure. 

Mora-Sero, I. Bisquert, J., Breakthroughs in the Development of Semiconductor-Sensitized Solar Cells Full./. Phys. Chem. Lett. 2010,1 3046-3052. 

The photosensitive nature of selenium makes it useful in devices that respond to the intensity of light, such as photocells, light meters for cameras, xerography, and electric eyes. Selenium also has the ability to produce electricity directly from sunlight, making it ideal for use in solar cells. Selenium possesses semiconductor properties that make it useful in the electronics industry, where it is a component in some types of solid-state electronics and rectifiers. It is also used in the production of ruby-red glass and enamels and as an additive to improve the quality of steel and copper. Additionally, it is a catalyst (to speed up chemical reactions) in the manufacture of rubber. 

Memming R (1978) The role of energy levels in semiconductor-electrolyte solar cells. J Electrochem Soc 125 117-123... 

Four different types of junctions can be used to separate the charge earners in solar cells (1) a homojunction joins semiconductor materials of the same substance, e.g., the homojunction of a p — n silicon solar cell separates two oppositely doped layers of silicon (2) a heterojunction is formed between two dissimilar semiconductor substances, e.g., copper sulfide, Cu S, and cadmium sulfide, CdS, in CuxS—CdS solar cells (3) a Schottky junction is formed when a metal and semiconductor material are joined and (4) in a metal-insulator-semiconductor junction (MIS), a thin insulator layer, generally less than 0.003-pim thick, is sandwiched between a metal and semiconductor material. 

Semiconductors used in solar cells are described under Solar Energy. 

In summary, it has been demonstrated that surface morphology is critically important in determining the performance of solar cells with layered compound semiconductors. Steps on structured surfaces of transition metal dichalcogenides have been identified as carrier recombination sites. The region defined by the depth of the space charge layer parallel to the van der Waals planes can be considered as essentially "dead" in the sense that its photoresponse is negligible. As the "step model" predicts, marked improvement in solar cell performance is found on samples with smooth surfaces. 

Based on our observations, we have reason to believe that single crystal performance will be approached in future thin film, polycrystalline semiconductor based solar cells with grain boundary recombination velocities reduced by strongly chemisorbed species. 

Electronic materials have already been encountered under imaging (e g., in OPCs) and displays (e.g., in OLEDs). Two areas worthy of further consideration are organic semiconductors and solar cells. 

Here we will discuss some concrete technologies based on photovoltaic (PV) effect in solar cells. Actually PV energy systems and computer technology based on the semiconductor p-n junctions that is why energy supply systems based on PV systems are very suitable to computer systems by electrical matching. 

ZnTe is usually applied in switching devices and in solar cells. It is one of the II—VI compound semiconductors with a direct band gap of 2.3 eV at room temperature. The electrodeposition of ZnTe was investigated by Sun et al. in the Lewis basic ZnCl2/l-ethyl-3-methylimidazolium ionic liquid containing propylene carbonate as a cosolvent at 40 °C [37]. 8-Quinolinol was added to the solution to shift the reduction of Te(IV) to more negative potential, thus facilitating the codeposition. The composition of the ZnTe deposits is dependent on the deposition potential and... 

In the most general situation, the current density in semiconductors and in solar cells is composed of electron and hole contributions jq = jh+ Je The relevant carrier concentrations ne(x) and rih(x) are subject to generation and recombination and have to obey continuity equations... 

Our interest in quantum dot-sensitized solar cells (QDSSC) is motivated by recent experiments in the Parkinson group (UW), where a two-electron transfer from excitonic states of a QD to a semiconductor was observed [32]. The main goal of this section is to understand a fundamental mechanism of electron transfer in solar cells. An electron transfer scheme in a QDSSC is illustrated in Figure 5.22. As discussed in introduction, quantum correlations play a crucial role in electron transfer. Thus, we briefly describe the theory [99] in which different correlation mechanisms such as e-ph and e-e interactions in a QD and e-ph interactions in a SM are considered. A time-dependent electric field of an arbitrary shape interacting with QD electrons is described in a dipole approximation. The interaction between a SM and a QD is presented in terms of the tunneling Hamiltonian, that is, in... 

The MigdaTs theorem is valid for wide-gap semiconductors where the fermi energy is approximately equal to a half of the gap. Semiconductors used in solar cells are usually wide-gap semiconductors. For example, the gap for a Ti02 is 3.2 eV, whereas a typical Debye frequency is about 0.1 eV. Thus, the expression for the photocurrent (130) holds true. 

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