Preparation and characterization of hydrogenated amorphous boron thin films and thin film solar cells produced by glow discharge decomposition methods. First quarterly report, January 1, 1979-March 31, 1979

Abstract

The energy gap of unhydrogenated amorphous boron is approximately 1.35 eV and therefore the theoretical maximum efficiency for amorphous boron solar cells is approximately 25%. However, in exact analogy with the situation previously existing for amorphous silicon, amorphous boron, without hydrogenation, has poor semiconducting properties due to defect states in the band gap. Large area amorphous boron films can be readily produced by either chemical vapor deposition or pyrolysis of diborane or boron tribromide. Such films do not contain more than minute quantities of hydrogen, however, due to the high (1000/sup 0/C) pyrolysis temperatures required. The substrate temperature during glow discharge decomposition methods, however, can be independently controlled. The decomposition of diborane in a glow discharge has been used to dope amorphous silicon with boron. The decomposition of diborane and of boron tribromide in hydrogen to produce thin films can reasonably be expected to result in amorphous boron thin films containing substantial quantities of hydrogen. If the effect of hydrogen in amorphous boron is similar to that of hydrogen in silicon, then hydrogenated amorphous boron thin films resulting from glow discharge decomposition of gaseous boron compounds could have very great potential as a solar cell material. Initial work and researchmore » plans are outlined.« less