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HL: Fachverband Halbleiterphysik
HL 79: Photovoltaics: Mainly Silicon
HL 79.8: Vortrag
Donnerstag, 17. März 2011, 16:30–16:45, FOE Anorg
Comparison of the annealing treatments of PVD and ALD Al2O3 passivated silicon for solar cell applications — •Frank Benner1, Maria Tarasova1,3, Steve Kupke1, Stefan Jakschik1, and Thomas Mikolajick1,2 — 1NaMLab gGmbH, Dresden, Germany — 2Lehrstuhl für Nanoelektronische Materialien, TU Dresden, Germany — 3Institut für Elektronik- und Sensormaterialien, TU Bergakademie Freiberg, Germany
One reason for the electrical losses in solar cells is surface recombination, which decreases the effective carrier lifetime. A highly p-doped area is commonly used for the passivation of silicon solar cell rear surfaces. Alternatively, an electric field can be established to prevent the carriers from diffusing towards the surface. Negative charges need to be near the silicon surface in the passivation layer to repel the minority carriers in the p-doped silicon. We have investigated Al2O3 layers to determine the density of interface states and fixed charges. Different annealing times, temperatures and process gases were investigated and their impact on the electrical characteristics and carrier lifetimes compared. Annealing in forming gas (N2/H2) was preferable to nitrogen. Moderate temperatures decreased the density of interface states, increased the density of fixed charges and, therefore, increased the carrier lifetime. A high temperature treatment degraded the passivation layers significantly. Al2O3 layers deposited with ALD were superior to PVD in carrier lifetimes even though the internal charge characteristics are similar. Our results indicate a higher concentration of impurities and a thicker interface layer.