Thin layers of aluminum oxide (Al2O3) are highly relevant for various high-efficiency silicon solar cell designs, as Al2O3 can provide an excellent passivation of crystalline silicon surfaces. One main part of this thesis deals with the evaluation, optimization and in-depth analysis of such passivating Al2O3 layers deposited by atomic layer deposition. In particular the results regarding the properties of the c Si/Al2O3 interface allowed to identify the underlying passivation mechanisms for various process variations.Another part of the thesis deals with the realization of p+nn+ silicon solar cells through the application and evaluation of industrially feasible technologies, i.e. for the front side boron-doped p+ emitter (based on the Al2O3 surface passivation), as well as for the diffusion and passivation of the rear side n+ back surface field.The excellent silicon surface passivation obtained in this thesis allowed in addition the experimental investigation of the Auger recombination in high-purity crystalline silicon with an improved precision, based on which results a new parameterization of the Auger recombination was developed. This parameterization was used to reassess the intrinsic efficiency limit of crystalline silicon solar cells.