Thin film technology for electron beam crystallized silicon solar cells on low cost substrates

In the design described a combination of nitride and carbide layers enables the recrystallization of a silicon absorber deposited on graphite or glass substrates. The interface layer siliconcarbide improves the wettability of the silicon film and the substrate during electron beam recrystallization. To prevent entrapment of deep impurities from the glass substrate aluminumnitride is used as a diffusion barrier. Furthermore AlN is used as a supporting mechanical layer during Si crystallization, and titaniumnitride as electrical backside contact. Additionally the absorption of light is enhanced due to reflection at the TiN layer. Efficient Si deposition rates up to 300 nm/min are achieved by means of a PECVD process using trichlorosilane (SiHCl₃) and hydrogen (H₂). Scanning of a line shaped electron beam across the silicon surface significantly enlarges the grains as well as it reduces impurities. A crystalline absorber thickness up to 20 μm is achieved without epitaxial growth. The layer interfaces are analyzed by scanning electron microscopy, x-ray diffraction and elastic recoil detection analysis.