The electronic structure of the interface between the boron-doped oxygenated amorphous silicon “window layer” (a-SiOx:H(B)) and aluminum-doped zinc oxide (ZnO:Al) was investigated using hard x-ray photoelectron spectroscopy and compared to that of the boron-doped microcrystalline silicon (μc-Si:H(B))/ZnO:Al interface. The corresponding valence band offsets have been determined to be (−2.87 ± 0.27) eV and (−3.37 ± 0.27) eV, respectively. A lower tunnel junction barrier height at the μc-Si:H(B)/ZnO:Al interface compared to that at the a-SiOx:H(B)/ZnO:Al interface is found and linked to the higher device performances in cells where a μc-Si:H(B) buffer between the a-Si:H p-i-n absorber stack and the ZnO:Al contact is employed.

The chemical and electronic properties of a-Si:H(B)/ZnO:Al and µc-Si:H(B)/ZnO:Al thin-film solar cell structures are studied by hard X-ray photoelectron spectroscopy (HAXPES). Using a combination of different X-ray excitation energies and deliberate sample design, we were able to select the probed volume, i.e., the silicon capping layer only or the silicon and zinc oxide layer (including the buried interface). For the a-Si:H(B) material, we find a higher deposition rate and a smaller value for the modified Auger parameter than for µc-Si:H(B). In addition, we find indications of a pronounced band bending limited to the very surface of the a-Si:H(B) and the µc-Si:H(B) layers, which is more distinct in the latter case.

Transparent conductive oxides are often used as transparent front electrodes for thin film solar cells. Besides their conductivity and transparency in the absorption range of the solar cell also the light scattering ability is important for light management. The TCOs are textured, e.g. as grown LPCVD ZnO:B or texture-etched ZnO:Al, and depending on their morphology they are differently adequate for their application as front electrode in solar cells. An evaluation method based on angular resolved light scattering (ARS) is presented in this paper. Measurement results and evaluation of different types of textured doped TCOs like reactively MF sputtered ZnO:Al (Zn:Al target), RF sputtered ZnO:Al (ZnO:Al2O3 target) and LPCVD ZnO:B are shown. A correlation between ARS and short-circuit density of a-Si:H/μc-Si:H p-i-n solar cells was found for LPCVD ZnO:B and reactively or RF sputtered and etched ZnO:Al until a saturation current was reached.