Highly efficient dielectric barrier discharge -lamp for generating and emitting an ultraviolet radiation comprising: - a discharge gap being at least partly formed and/or surrounded by - at least an inner wall and - an outer wall, - each with an inner surface (2a, 3a), facing the discharge gap and - an outer surface (2b, 3b) arranged opposite of and directed away from the corresponding inner surface (2a, 3a), whereby at least one of the walls is a dielectric wall and/or one of the walls (2, 3) has an at least partly transparent part, - a filling located inside the discharge gap, - at least two electrical contacting means, - a first electrical contacting means associated with the inner wall and - a second electrical contacting means associated with the outer wall, and at least one luminescent coating layer arranged at/on and at least partly covering at least a part of the respective wall's inner surface, arranged such, that at least a part of the radiation generated by means of a gas discharge inside the discharge gap can pass the luminescent coating layer from the discharge gap to the surrounding of the DBD-lamp, whereby at least one of both walls (2, 3) is at least partly arranged with directing means, so that the diffusive radiation, which is generated by means of a gas discharge inside the discharge gap and/or emitted by the luminescent coating layer, is directed in a defined way through at least one of the walls (2, 3) with reduced losses due to absorption effects and the like, whereby the directing means are arranged as at least one reflecting coating layer arranged at/on the inner surface of the inner wall, at/on the inner surface of the outer wall, at least partly at/on the inner surface of the inner wall or at least partly at/on the inner surface of the outer wall, and wherein the reflecting coating layer is coated by a protective layer, characterized in that the protective layer is a highly reflective ultra fine particle oxide layer. - a discharge gap being at least partly formed and/or surrounded by - at least an inner wall and - an outer wall, - each with an inner surface (2a, 3a), facing the discharge gap and - an outer surface (2b, 3b) arranged opposite of and directed away from the corresponding inner surface (2a, 3a), whereby at least one of the walls is a dielectric wall and/or one of the walls (2, 3) has an at least partly transparent part, - a filling located inside the discharge gap, - at least two electrical contacting means, - a first electrical contacting means associated with the inner wall and - a second electrical contacting means associated with the outer wall, and at least one luminescent coating layer arranged at/on and at least partly covering at least a part of the respective wall's inner surface, arranged such, that at least a part of the radiation generated by means of a gas discharge inside the discharge gap can pass the luminescent coating layer from the discharge gap to the surrounding of the DBD-lamp, whereby at least one of both walls (2, 3) is at least partly arranged with directing means, so that the diffusive radiation, which is generated by means of a gas discharge inside the discharge gap and/or emitted by the luminescent coating layer, is directed in a defined way through at least one of the walls (2, 3) with reduced losses due to absorption effects and the like, whereby the directing means are arranged as at least one reflecting coating layer arranged at/on the inner surface of the inner wall, at/on the inner surface of the outer wall, at least partly at/on the inner surface of the inner wall or at least partly at/on the inner surface of the outer wall, and wherein the reflecting coating layer is coated by a protective layer,