AVS 52nd International Symposium
    Thin Films Monday Sessions
       Session TF+EM-MoM

Paper TF+EM-MoM9
Silicon Thin Films from Trichlorosilane for Electron Beam Recrystallized Solar Cells

Monday, October 31, 2005, 11:00 am, Room 306

Session: Thin Films for Photovoltaic and Energy Applications
Presenter: C. Groth, Hamburg University of Technology, Germany
Authors: C. Groth, Hamburg University of Technology, Germany
K. Ong, Hamburg University of Technology, Germany
Correspondent: Click to Email
The project's aim is to produce polycrystalline thin film solar cells on low cost substrates, especially on float glass. The chemical processing is entirely dry, which leads to high efficiency and throughput. There is no size limitation using this sequence of processing; even the in-line production of complete solar panels is feasible. An intermediate Tungsten (W) layer of approximately 1 µm is used to maintain mechanical stability at high temperatures. Furthermore, it is used as diffusion barrier during the recrystallisation process and serves as back surface reflector and electrical contact. Two deposition processes are currently under investigation: DC-magnetron sputtering and plasma enhanced chemical vapour deposition (PECVD) using tungstenhexafluoride (WF@sub 6@) as precursor. Both processes are using substrate temperatures of ~400 °C. Analysis using XRD (x-ray diffraction) shows formation of @alpha@-W for sputtered layers while PECVD layers consist of @alpha@- and @beta@-W, depending on the process parameters. The silicon (Si) basis with a thickness of 15 µm is deposited by PECVD directly from trichlorosilane (SiHCl@sub 3@) as precursor at high rates of ~200 nm/min. Substrate temperature during the process is ~550 °C. RF frequencies of 13.56 MHz are used in both PECVD processes. P-doping of the basis is done in-situ using borontrichloride (BCl@sub 3@). The nanocrystalline silicon film is recrystallised by a line-shaped electron beam at high velocities of about 60 mm/s. This leads to grain sizes of up to several 100 µm. A PECVD deposited amorphous silicon layer will be used as hetero emitter to complete the solar cell.