Back surface field

Figure 13 shows typical results of the degradation of crystalline Si solar cells having a back surface field and reflector structure (Si-BSFR), which were qualified by National Space Development Agency of Japan (NASDA) for space usage, when irradiated by 10-MeV protons and 1 -MeV electrons. The pn junction of the cell samples, with a size of 2 cm x 2 cm X 50 pm, was fabricated by phosphorus (P) doping to a depth of 0.15 pm into boron... 

Figure 2.106 Energy band diagram of the structure of p -lnP substrate (doped in the 10 cm range) and the homoepitaxial p-lnP film (doped in the low 10 cm" range) showing a back surface field band alignment.

In order to optimise V two methods used in Si homojunction cells may be considered. T ese are the use of low resistivity base material and the use of a back surface field with high resistivity base material. Both of these modifications have been made for p-type MIS cells and they are discussed later in para 4.5. The other parameter that can be optimised is (f) and to do this various barrier metals have been used as indicated in table 2. 

The second technique for improving V by introducing a back surface field has been demonstrated by Tarr and Pulfrey . ... 

King, R. R. Sinton, R. A. Swanson, R. M. In Front and Back Surface Fields for Point-Contact Solar Cells, Photovoltaics Specialists Conference, IEEE. 1988 pp. 538-544. 

As light propagates through the stratified layers, it is affected by two basic mechanisms, shown in Figure 3.2. The first mechanism concerns the transmission of the light through a film, and the second arises from reflection and refraction at an interface. An additional subscript, (0,1), has been added to denote whether the electric field exists either at the inside front surface of a film, or at the inside back surface of a film, respectively. In both cases, these interactions induce the following linear transformations ... 

An electric field can be applied to an insulator with no electrode present through electrostatic charging (sometimes called xerographic charging) [42]. The process involves the generation of ions in the vicinity of a metal point or fine wire by the field emission of electrons from (or to) the metal and the subsequent (or prior) capture (or release) of the electrons by gas atoms. The ions are then drifted to the specimen surface in an applied field and, under certain circumstances, the ions remain stable on the surface to generate an electric field between that surface and the back surface that has been held at ground potential. For this process to take place the interaction between the ions and solid surface must create an electronic level (the so-called chemisorption level of the ion on the insulator surface) that lies well within the band gap of the... 

Adhesion is a more difficult problem. There are many chemically different interfaces in a laminant stack glass-EVA, EVA-solar cell surface (oxidized silicon or some anti reflection (AR) coating), cell back surface metallization-EVA, EVA-back sheet, and EVA-bus bars (copper or tinned copper). Each of these interfaces is important, because mechanically good adhesive bonds will often fail by delamination after exposure to humidity in the field. Water vapor will permeate through polymers and, if there is a non-chemically bonded surface, water may collect and cause failure by displacement. Tables I, II, and III provide details of some of the research efforts in adhesion. 

In Eqs. (6.38-6.40) and (6.41-6.43), A, B, R, and T are unknown coeflftcients, which are determined the boundary conditions that require continuity of the electric and magnetic field components, and Hy, at the front and back surfaces, i.e., z = 0 and z = a. By imposing four boundary conditions and solving four algebraic equations, the coefficients can be obtained as follows ... 

To verify the validity of the present finite element calculation of the temperature filed of the samples during ablation. The calculated temperature curves of the ablated surface center and back surface center of the samples are compared with the measured temperature curves. It is found that the calculated temperature curves are consistent with the experimental results. For instance, the temperature curves at ablated surface centers and the back surface centers of the 30TiCAV and 30ZrCAV samples are shown in Figure 10. The calculated temperature curves agree the measured curves. It seems that the present finite element model could be used for the analysis of the temperature field upon ablation/thermal shock. 

A catalyst may play an active role in a different sense. There are interesting temporal oscillations in the rate of the Pt-catalyzed oxidation of CO. Ertl and coworkers have related the effect to back-and-forth transitions between Pt surface structures [220] (note Fig. XVI-8). See also Ref. 221 and citations therein. More recently Ertl and co-workers have produced spiral as well as plane waves of surface reconstruction in this system [222] as well as reconstruction waves on the Pt tip of a field emission microscope as the reaction of H2 with O2 to form water occurred [223]. Theoretical simulations of these types of effects have been reviewed [224]. 

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