In order to realize transparent CdTe solar cells, we reduced the absorber layer thickness to as little as 0.25 mu m using a low-temperature close space sublimation process. Furthermore, we developed a transparent ZnO:Al back contact with a high transmittance of more than 65 % over the whole wavelength range of 400-1300 nm. Thin solar cells with this back contact achieve performances comparable to solar cells with a low-ohmic non-transparent Cu-Au back contact. These beneficial properties suggest the application in a tandem cell configuration. The viability of this concept is demonstrated for a mechanically stacked tandem configuration with CdTe as top filter and CuInSe2 as bottom cell. (C) 2013 Elsevier B.V. All rights reserved.