Recent developments of silicon thin film solar cells on glass substrates

Among various semiconductor technologies applied in photovoltaics, thin-fil m technologies offer several attractive features, both technically and econ omically. Recent developments of silicon thin-film devices predominantly ba sed on amorphous silicon (a-Si), are described. Particular emphasis is plac ed on the importance of the substrates that consist of glass coated with a transparent conductive oxide (TCO) to serve as front contact layer of the p hotovoltaic film combination. The electrical conductivity and optical absor ption of the TCO substantially affect the energy conversion efficiency of s olar modules. An essential enhancement of the light absorption within the p hotoactive a-Si layer is derived from a surface texture of the TCO, that pr ovides index-grading for lower front reflection, and light scattering to re sult in light trapping due to total internal reflections within the a-Si. T he requirements for optimal TCO properties are reviewed in the context of t heir availability. Additionally, novel cell structures involving microcryst alline silicon, are expected to lead to higher efficiencies. Thin-film tech nologies, led by those based on a-Si, will take on an increased role in mod ule production worldwide, which is consistent with favorable manufacturing cost expectations. (C) 1999 Elsevier Science S.A. All rights reserved.