How to make solar cells

How to make solar cells

was constructed as a light source for photochemical experiments, consisting of a front-surfaced concentrator on a telescope-type mounting. It is used ...

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was constructed as a light source for photochemical experiments, consisting of a front-surfaced concentrator on a telescope-type mounting. It is used without a heliostat. The mirror used for these studies is a two-foot paraboloid of stellite metal (cobalt-chromiunl-tungsten alloy).

Laszlo, Tibor S., Research and Advanced Development Div., Avco Corp., Wilmington, Mass., U.S.A., “New Techniques and Possibilities in Solar Furnaces,” United Nations Conference on New Sources of Energy, Rome, 1961, 30 p. Illus. The limitations on experimentation in a solar furnace are discussed: (1) small size of the hot zone; (2) heating takes place only at the front of the sample; (3) the non-uniform flux across the image area. Amelioration of the limitations are described together with the accompanying instrumentation and some new methods of manufacturing solar furnace components. Determinations are listed for which the restrictions specific to the solar furance may be, according to the author’s suggestions,, overcome. They are concerned with the following categories: (a) Measurement of physical properties. (b) Observation and measurement of chemical properties. (c) Special operations such as growing of simple crystals, zone refining and high temperature fabrication. N., Laboratory of Solar Energy, National Scientific Research Commission, Montlouis, PyreneesOrieutales, France, “Temperature Measurements in the Solar I?urnace,” IJnited Nations Conference on New Sources of Energy, Rome, 1961, 31 p. Illus. French language only.

lcoex,

VIII-Thermionic Hernquist,

Ii. G.,

oratories,

“Thermionic

14th

Conference,

Annual

4 p., May

Converters,”

Proceedings 17,

18,

19,

RCA

I’owcr 1960

Lab-

Sources

Illus.

There are three main problem areas for the thermionic energy converter, namely: a) Space charge problems. That is, to devise methods t)o assure an unhindered flow of electrons from cathode to anode. b) Materials problems. This is the search for cathode and anode materials having the right electrical, mechanical. and thermal properties. c) Technological problems. These are problems connected with the fabrication of devices and depend to a large extent on the properties of the heat source to be used. The present version of the cesium vapor type thermionic energy converter calls for heat source temperatures in excess of 2000 deg C. Some of the construction and application problems for this type of converter are discussed. Considerable progress towards solving these problems for solar, chemical and nuclear energy applications is demonstrated. X-Photoelectric, and

Photovoltaic,

Photogalvanic

Piezoelectric

Rappaport

and H. I. Moss,

P.,

Princeton,

N.

$J.,

U.S.A.,

Conversion

of Solar

ference

New

on

Energy,”

Sources

RCA

“Low-Cost of

United Energy,

Laboratories, Photovoltaic Nations

Con-

Rome,

1961,

10 p. Illus.

The optical pyrometry of substances treated in the solar furnace is subject to a major source of error. The parasitic reflections of the incident radiation generally make the readings too high. This situation can be alleviated by a combination of filters. The filter placed in the path of the incoming solar radiation has an intense absorption band in a very definite wavelength region, but passes as much of the remaining radiation as possible, to avoid excessive diminution of the incident radiation. Another method is to occlude the solar radiation with a screen when measuring the temperature. There is a temperature gradient, often considerable, in substances whose surface is directly subjected to the action of radiation of high irradiance. In the case of molten substances, black-body formation is easily accomplished by melting in centrifugal furnaces in order to form cavities of relatively large size with an orifice corresponding to the focus of the furnace. Finally, t,he paper discusses a method using rapidresponse pyrometers to study various transitory phenomena, and, in particular, to measure the solidification points of refractory oxides melting between 1800 and 2700 deg C, as well as the temperature of certain transformat,ions.

The purpose of this paper is to indicate how the photovoltaic effect (solar cells) can be used as an energy source in terrestrial applications especially for under-developed countries. Present-day solar cells are much too expensive to provide electrical power for everyday terrestrial applications. The major reason for this is the need to make single crystals. Solar cells that are made by a deposition technique from a suitable raw material would be inherently inexpensive. A cost of $1 to $10 per square foot of a 10 percent efficient solar cell would probably bring the cost into the range of economic feasibihty for home use. A practical and inexpensive cadmium sulfide solar cell that is 3.5 percent efficient has been achieved. Such cells may be perfected to yield 6 percent, however! with further research other materials such as silicon may yield an inexpensive filn-type cell with efficiencies approaching 10 percent.

Glaser, Peter E., Arthur D. Little, Inc., Cambridge, Massachusetts, IJ.S.A., “Industrial ApplicationsThe Challenge To Solar Furnace Research,” United Nations Conference on New Sources of Energy, 26 p. Illus.

1. The silicon wafers, obtainable from International Rectifier Corp., are lap-ground with 280 mesh Carborundum. 2. The cells are lightly etched in a mixture of HN03 (nitric acid). 3. One surface is painted with a solution of boric acid, boric oxide or commercial grade borax. 4. To diffuse the boron into the surface, wafers are heated in air for about 10 minutes at about 1,050 deg C and cooled to room temperature. 5. The untreated side is again lap-ground with carborundum. 6. The cells are treated with HF to remove oxides. 7. Part of the diffused surface is covered with acid-resisting tape. 8. Exposed surfaces are electroplated in electrodless nickelplating solution. (The formula and summary of the process appear later in the article.) 9. Plated surfaces are tinned with solder, and lends are attached. 10. The edges of the wafer are ground with Carborundum. 11. HF and HNO, etchant is applied t,o the edges to cornplete the separat,ion of p- and n-areas.

This paper discusses recent developments in the construction of reflecting surfaces, the measurement of the most imexperimental research already accomportant variables, plished, and the potential of industrial applications of solar furnaces. Industry would look to solar energy only if it could be demonstrated that such power costs less than the conventional varieties. To be competitive the cost of the reflector and its auxiliary equipment should not exceed $2.00 per square foot. (This estimate is based on an equivalent cost of fuel for the energy delivered.) In many industrial processes extremely high temperatures and thus collectors of fine quality may not be required, t,herefore, some of the newer plastic material reflect.ors may permit, cost,s to be reduced to about $1.00 per square foot.

Vol. 7, No. 4, 1963

Chapin, D. M., “How To Make Solar Cells”, Reprinted from Radio-Electronics, March, 1960, Bell Telephone Laboratories, Murray Hill, N. .J.? 8 p. Illus.

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