Occurrence of Random Photovoltaic Barriers in Photoconductive Layers

Abstract

In two previous communications^1,2 the photo-conductive properties of lead sulphide layers and a new photovoltaic effect were described. The latter effect is essentially a property of the semi-conductor and is not associated with the electrodes. A theory of the effect was outlined which attributed the photo-e.m.f. to the barrier between regions of excess and defect semi-conductors. It was further postulated that, in an apparently homogeneous photoconductive layer showing no external photo-e.m.f., there existed regions distributed at random which were predominantly either excess or defect semi-conductors. The photoconductive properties of the layer were also attributed to the barriers between these regions. Experimental evidence has now been obtained to justify this assumption.