Low-temperature plasma processes for silicon thin-film deposition : from amorphous to crystalline

Abstract

Plasma processes enable the deposition of a wide variety of materials under non-equilibrium conditions. Here we retrace the evolution of the silicon thin-film industry: from hydrogenated amorphous silicon (a-Si:H) in the 1980s to polymorphous silicon and nano- and micro-crystalline, not forgetting its respective alloys with carbon, germanium and oxygen, which gave rise to band gap engineering and the manufacture of tandem and triple junction cells, and enabled spectacular development of electronics on large surfaces, particularly with flat screens. The quest for greater efficiency has led the industry to take an interest in radial junction cells and the deposition of a-Si:H thin films on crystalline silicon to produce so-called heterojunction cells, which hold the efficiency record for crystalline silicon-based technology. We'll also be outlining the future of this sector: the development of crystalline silicon layers epitaxialized at 200°C, opening the way to thin, flexible crystalline cells. What's more, this low-temperature epitaxy has also been demonstrated on GaAs, enabling the creation of c-Si/GaAs tandem cells.

Biography

Pere Roca i Cabarrocas is Director of Research at the CNRS, Professor at the École Polytechnique and Scientific Director of the IPVF. He obtained his doctorate from the University of Paris-VII in 1988. After a post-doctorate at Princeton University, he joined the LPICM at École polytechnique. From 2012 to 2020, he was Director of LPICM and of the French Photovoltaic Federation. He has thirty years' experience in the plasma deposition of silicon-based thin films, and has used in situ diagnostic techniques to understand the growth of materials and apply them to the production of devices such as solar cells and transistors. More recently, he has applied plasma-synthesized silicon nanocrystals for epitaxial growth and extended plasma processes to the growth of silicon nanowires. He was awarded the École Polytechnique Innovation Prize in 2009 and the CNRS Silver Medal in 2011. He has published over five hundred articles in peer-reviewed journals, holds thirty-eight patents and has supervised fifty doctoral students.