The advantages and limitations of photovoltaic solar modules for energy generation are reviewed with their operation principles and physical efficiency limits. Although the main materials currently used or investigated and the associated fabrication technologies are individually described, emphasis is on silicon-based solar cells. Wafer-based crystalline silicon solar modules dominate in terms of production, but amorphous silicon solar cells have the potential to undercut costs owing, for example, to the roll-to-roll production possibilities for modules. Recent developments suggest that thin-film crystalline silicon (especially microcrystalline silicon) is becoming a prime candidate for future photovoltaics.

This paper describes the use, within p–i–n‐ and n–i–p‐type solar cells, of hydrogenated amorphous silicon (a‐Si:H) and hydrogenated microcrystalline silicon (μc‐Si:H) thin films (layers), both deposited at low temperatures (200°C) by plasma‐assisted chemical vapour deposition (PECVD), from a mixture of silane and hydrogen. Optical and electrical properties of the i‐layers are described. These properties are linked to the microstructure and hence to the i‐layer deposition rate, that in turn, affects throughput in production. The importance of contact and reflection layers in achieving low electrical and optical losses is explained, particularly for the superstrate case. Especially the required properties for the transparent conductive oxide (TCO) need to be well balanced in order to provide, at the same time, for high electrical conductivity (preferably by high electron mobility), low optical absorption and surface texture (for low optical losses and pronounced light trapping). Single‐junction amorphous and microcrystalline p–i–n‐type solar cells, as fabricated so far, are compared in their key parameters (Jsc, FF, Voc) with the [theoretical] limiting values. Tandem and multijunction cells are introduced; the μc‐Si: H/a‐Si: H or [micromorph] tandem solar cell concept is explained in detail, and recent results obtained here are listed and commented. Factors governing the mass‐production of thin‐film silicon modules are determined both by inherent technical reasons, described in detail, and by economic considerations. The cumulative effect of these factors results in distinct efficiency reductions from values of record laboratory cells to statistical averages of production modules. Finally, applications of thin‐film silicon PV modules, especially in building‐integrated PV (BIPV) are shown. In this context, the energy yields of thin‐film silicon modules emerge as a valuable gauge for module performance, and compare very favourably with those of other PV technologies. Copyright © 2004 John Wiley & Sons, Ltd.

This contribution describes the introduction of hydrogenated microcrystalline silicon (mc-Si:H) as novel absorber material for thin-film silicon solar cells. Work done at IMT Neuch# atel in connection with deposition of mc-Si:H layers by very high frequency glow discharge deposition is related in detail. Corresponding layer properties w.r.t. material microstructure, hydrogen content, stability and electronic transport are referred to. Basic properties of single-junction, entirely microcrystalline, thin-film silicon solar cells are related: Spectral response, stability w.r.t. light-induced degradation, basic solar cell parameters (V oc ; J sc and FF) obtained by IMT Neuch# atel and by other laboratories are listed and commented; the deposition rate issue is addressed. Finally, microcrystalline/amorphous, i.e. ''micromorph'' silicon tandem solar cells, are described, together with recent developments on the research and industrial front.

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