The invention relates to a method for producing syngas by means of solar radiation, in which the reactor of a receiver-reactor is periodically heated via an aperture provided in the same for solar radiation by means of the solar radiation to an upper reduction temperature for a reduction process and subsequently cooled to a lower oxidation temperature for an oxidation process in the presence of an oxidation gas, wherein the sunlight is guided through an absorption chamber onto an absorber configured as a reactor, which includes a reducible/oxidizable material, and wherein a gas that absorbs the black-body radiation of the absorber is guided through the absorption chamber and the absorption chamber is configured so that the back radiation of the absorber through the aperture is essentially absorbed by the gas. Radiation losses caused by back radiation of the black-body radiation exiting the optical aperture are thus avoided in accordance with the invention. The heat of the back radiation, however, can be utilized directly in the heat-transporting fluid and is available for a flexible usage. The receiver-reactor has a simple design and is suitable as a low-cost receiver-reactor.