Aluminum doped thermomigrated silicon channels for high voltage solar cells: structure and electrical properties

Abstract

The results of a study of the real structure, electrical and photovoltaic characteristics of a monolithic solar module of 15 cells, made based on an array of p-n junctions in a Si (111) silicon wafer, are presented. The p-n junctions were formed by the boundaries of through vertical Al-doped (C= (0.95-1.05)×1019 cm-3) Si channels 100 μm wide at a distance of 3 mm. The perfection of the crystal lattice in the channel and near its boundaries has been investigated by X-ray methods: projection topography and high-resolution diffractometry in the transmission and reflection geometry. It is shown that the channel-matrix interface is coherent and there are no misfit dislocations on it. Typical defects in the p-channel are dislocation half-loops, which are located parallel to the surface of the wafer in its near-surface layer. The investigated solar 15-cells module demonstrates an efficiency of 13% at output 7.5 V and 30 mA. These photovoltaic parameters are comparable with the main electrical parameters of the planar analogues, despite the design features of the Si(Al) channels and the presence of structural distortions near the boundaries of the substrate matrix.