The internal resistance of the selenium rectifier photocell, with special reference to the sputtered metal film

Abstract

This paper describes the effect of the internal resistance (other than the barrier-layer) of the selenium rectifier photocell upon its observed characteristics. Methods of measuring the resistance of the selenium layer are cited. This resistance is of the order of 10 ohms in most modern cells. A method of measuring the resistance of the sputtered film is also described. This method is based on measurements, on unlacquered cells, of the distribution of potential over the film resulting from the flow of photocurrent across it when the cell is exposed to a steady uniform illumination. The results obtained with four cells tested gave values between 100 and 600 ohm.cm. for the resistivity of the film. They suggest that for a cell of normal type the value is in the region of 100-300 ohm.cm., while a value exceeding 500 or 600 ohm.cm. is likely to be associated with non-uniformity of the film over the area of the cell, and less satisfactory performance at high values of illumination. The experiments were made on cells of a production type supplied by a regular maker