Silicon Thin Films: Functional Materials for Energy, Healthcare, and IT Applications

The authors review selected topics in the development of hydrogenated amorphous silicon (a-Si:H), from its emergence some 50 years ago to its present status as a mature thin-film semiconductor, with market successes including flat-panel displays, solar modules, and x-ray scanners. By altering process gas mixtures and deposition conditions, films with a range of atomic, structural, and amorphous/crystalline phase compositions may be deposited, offering tunable bandgap, refractive index, and light-scattering properties. Films thus functionalized have greatly increased scope and utility. Three emerging applications are reported, and more extensive sections on two topics of current importance are presented: 1) Multi-junction thin film silicon solar cells for water splitting applications; and 2) thin-film silicon solar cells on flexible substrates.