Details

Autor(en) / Beteiligte

• KRAUSE, Jonas
• WOEHL, Robert
• RAUER, Michael
• SCHMIGA, Christian
• WILDE, Jürgen
• BIRO, Daniel

Titel

Microstructural and electrical properties of different-sized aluminum-alloyed contacts and their layer system on silicon surfaces

Ist Teil von

• Solar energy materials and solar cells, 2011-08, Vol.95 (8), p.2151-2160

Ort / Verlag

Amsterdam: Elsevier

Erscheinungsjahr

2011

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The firing of screen-printed aluminum pastes is well established for the formation of a back surface field (BSF) and back contacts since many years in silicon solar cell fabrication. In this paper we investigate the electrical and microstructural properties of Al-alloyed contacts and their layer system, consisting of (i) the Al-doped p[super]+-layer (2-14 [micro]m), the eutectic layer (1-15 [micro]m) and the layer of paste residuals (20-100 [micro]m). We show the influence of process parameters like the amount of printed paste, the alloying time and the peak temperature. Special emphasis is devoted to the properties of small alloyed screen-printed aluminum structures for the formation of local aluminum back contacts. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), electrochemical capacitance voltage (ECV) and conductivity measurements have been applied to characterize the samples. A simple model is qualitatively augmented to describe all effects occurring in a technical alloying process. For example, for increasing aluminum amounts, a saturation of the p[super]+-layer thickness was found in the range of 10 mg/cm[super]2. For small screen-printed structures, the p[super]+-layer is formed very homogenously and with a greater thickness compared to samples with a full-area Al metallization, which have been processed with similar alloying conditions. For the eutectic layer a high electrical conductivity of about 16x10[super]6 S/m, only 2-3 times below that of pure aluminum has been determined. This is advantageous for the lateral conductivity especially for high paste amounts and small structures, which feature a relatively thick eutectic layer.