Because of the danger in the materials used, and the risk of contaminating the delicate cells, most companies require near perfect sanitation in work rooms. "Space suits" are often required when working with the silicon wafers.
Every company has its own procedure for making photovoltaic cells. This is a highly competitive industry where procedures are kept confidential.
Every company tries to produce more efficient cells than others. All of this competition has brought on many scientific advances, and has resulted in cells approaching 25% efficiency.
An Average Cell
Today, most cells measure around 5 by 10 centimeters. Usually, they produce about one watt of electricity, and have an efficiency around 20%.
Sandia National Laboratories
The Department of Energy runs a multi-program national security lab called Sandia, located in California and New Mexico. Sandia has a Photovoltaic Systems Assistance Center, which specializes in researching photovoltaic science.
There are a wide variety of corporations that deal with the production of solar cells or cell ingredients, including Astropower, Carborundum, Ferro, and Solarex.