Transparent CdTe solar cells with a ZnO:Al back contact

Abstract In order to realize transparent CdTe solar cells, we reduced the absorber layer thickness to as little as 0.25 μm 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 CuInSe 2 as bottom cell.