Grain Boundary Recombination in Thin Film Silicon Solar Cells

WERNER, J.-H.; TARETTO, K. R.; RAU, U.

DIFFUSION AND DEFECT DATA, SOLID STATE DATA. PART B, SOLID STATE PHENOMENA

Trans-Tech

Lugar: Zurich; Año: 2001 p. 299 - 304

1012-0394

The efficiency of polycrystalline solar cells depends strongly on recombination at grain boundaries. We analyze the open circuit voltage Voc of thin film Si cells over six orders of magnitude in grain size g and obtain typical recombination velocites S of S=105 to 107 cm/s for g>1&mum, if we ascribe the whole recombination to grain boundaries within the bulk material, outside the space charge region. With such S-values, the Voc of nanocrystalline and microcrystalline Si with g>1 &mu m would range far below 500 mV, yielding efficiencies far below 10%. The experimental efficiencies around 10% and Voc-data up to Voc=550 mV are therefore only understood by a much lower S, between S=101 and 103 cm/s. We ascribe this finding to electrically inactive symmetrical [110]-tilt boundaries occurring in the small grained samples, which were all reported to have a {220}-texture.