Photoelectric and Related Properties of the Potassium—Antimony—Caesium Photocathode†

Abstract

Measurements of photoelectric emission, optical absorption, photoconductivity and electrical conductivity have been used to construct an energy band scheme for the K₂CsSb photocathode. The spectral sensitivity of the photoelectric yield may be fitted to Spicer's equation for photoemission from the valence band of semiconductors, and leads to a value of 2-1 ev for the depth of the top of the valence band below vacuum potential. Photoconductivity and optical absorption measurements suggest a band gap of about 1-0 ev. The temperature variation of electrical conductivity suggests the existence of impurity centres between about 0-2 and 0-5 ev above the top of the valence band. The thermionic work function, determined by a contact potential difference method, is about 1 6 ev.