Ion layer gas reaction (ILGAR®) is a non-vacuum, thin-film deposition technique developed and patented by the group of Professor Dr. Christian-Herbert Fischer at the Helmholtz-Zentrum Berlin for materials and energy in Berlin, Germany. It is a sequential and cyclic process that enables the deposition of semiconductor thin films, mainly for (although not restricted to) photovoltaic applications, specially chalcopyrite absorber layers and buffer layers. The ILGAR technique was awarded as German High Tech Champion 2011 by the Fraunhofer Society. ILGAR is a chemical process that allows for the deposition of layers in a homogeneous, adherent and mechanically stable form without using vacuum or high temperatures. It is a sequential and cyclic process which can be automated and scaled up. It consists basically of the following steps: Application of a precursor solution on a substrate by dipping (Dip-ILGAR) or spraying (Spray ILGAR). Reaction of the dry solid precursor layer with a hydrogen chalcogenide gas. These steps are repeated until the desired layer thickness is obtained. In the case of spray-ILGAR, the spray deposition of the ionic layer is performed using similar equipment to atmospheric pressure aerosol assisted chemical vapour deposition or spray pyrolysis. Spray pyrolysis can be regarded as a simplified version of the spray ILGAR process, where there is no reaction of the precursor layer with a reactant gas. The cyclical nature of this process makes it similar to atomic layer deposition (ALD), which is also used for buffer layer deposition. Applications The applications of the ILGAR and spray-pyrolysis techniques at the Helmholtz-Zentrum Berlin lie mainly in the field of chalcopyrite thin-film solar cells, although these techniques can be used for other applications involving substrate coating with thin films. The following list summarizes the applications of these techniques: Buffer layers for chalcopyrite-based thin-film devices: Replacement of the standard CdS by ecologically more favorable materials (In2S3, etc.) deposited using Spray-ILGAR on different absorber materials. Nano-dots passivation layers: nanodots can be deposited in a controlled way using the spray ILGAR technique. ZnS nanodots have been used as passivation layers-point contact buffer layers in chalcopyrite based thin-film solar cells. These dots (5–10 nm in diameter) act as a passivation layer at the absorber-buffer interface which results is some cases in an efficiency gain up to 2% absolute. Al2O3 barrier layers: Thin-film solar modules on metallic substrates like steel foil need a barrier layer between substrate and Mo back-contact for electrical insulation and to prevent