BARTOL ~SSARCH
The photoelectric cell is fast becoming an FOUNDATION indispensable unit in the modern laboratory, Communication No. 23. and, although there are some cells to be had on the commercial market, they may not always satisfy the particular physical or electrical requirements of special applications. In answer to just such a need, this laboratory has developed a method by which photoelectric cells of high sensitivity can be made. There is, we think, nothing unique in the method and there may be other ways which we have not thought of which are better. All that we claim for the following instruction is that it describes in detail a procedure by which photoelectric cells can be easily produced in the laboratory with a fairly high degree of certainty that the cells will turn out successfully and be reasonably uniform in their sensitivity.
In the most general terms, the method usually followed in the production of this type of photoelectric cell is as follows:
(I) The cell is designed and constructed carrying two electrodes, the "outside" electrode connecting to the lightsensitive surface, and the "central" electrode, which is the collector of the electrons.
(2) The tube is connected to a suitable vacuum system, evacuated, and baked out at high temperature.
(3) The potassium is distilled in "vacuum" through part of the system and condensed on the surface of the cell.
(4) Hydrogen is then introduced to suitable pressure and a glow discharge is operated between the "outside" and the "central" electrodes until the potassium-hydride surface so produced shows the maximum sensitivity.