Photovoltaic Cells

Abstract

A photovoltaic cell incorporating a semiconductor element (10) composed entirely of a single conductivity type. A biasing agent (26) having a work function different from that of the semiconductor element overlies a face of the element and produces a band bending and thus an electric field in a space charge region. Electrodes are in contact with the semiconductor element within the space charge region. Carriers generated by light absorbed in the semiconductor element are accelerated toward the electrodes by the field.

1 . A method of generating electricity comprising the steps of:
 (a) maintaining a first portion of a first surface of a semiconductor in direct contact with a biasing agent having a normal Fermi level different from the normal Fermi level of the semiconductor, whereby the biasing agent produces band bending in the semiconductor, while also maintaining a second portion of the first surface separate from the first portion in direct contact with a first electrode and maintaining the first electrode out of direct conductive contact with the biasing agent; and   (b) during step (a), maintaining a second electrode in contact with the semiconductor at a location remote from the first surface;   (c) during steps (a) and (b), directing light into semiconductor so that at least some of the light is absorbed by the semiconductor and the absorbed light promotes electrons from the valence band to the conduction band; and;   (d) collecting the resulting electrical current at the electrodes.   
     
     
         2 . A method as claimed in  claim 1  further comprising directing the electrical current through a load connected between the first and second electrodes. 
     
     
         3 . A method as claimed in  claim 1  further comprising the step of blocking transmission of light into a region of the semiconductor aligned with the first electrode. 
     
     
         4 . A method as claimed in  claim 3  wherein the first electrode is opaque and the blocking step is performed at least in part by the first electrode. 
     
     
         5 . A method as claimed in  claim 1  wherein the semiconductor absorbs the light in a direct transition process