Recrystallized silicon on SiO2-layers for thin film solar cells

Using optically heated furnaces, silicon layers of 30-50 μm thickness were recrystallized on 2 μm thick SiO₂ intermediate layers which were deposited on Si substrate wafers. In one case, the SiO₂-layers were prepared with 1% of the area being opened as contact and seeding holes, and the recrystallization was done with a large area heater (LAH). In the second case, a zone melting recrystallization (ZMR) process was applied on a compact SiO₂-layer without any seeding. Since the active layer is not electrically contacted to the substrate, a newly developed interdigitated front grid was used to contact both the base and the emitter from the front side. The differential spectral response of the solar cells prepared on a SiO₂-intermediate layer with seeding holes depends on the bias light for long wavelengths, where the contribution of the base is dominant. Rocking curve analysis was used to characterize the crystallographic structure of the recrystallized layers. It was found that the seeding holes mostly caused a tiled structure of squares in the silicon layer which, like the substrate, was completely (100)-oriented