μc-Si SOLAR CELLS BY DIRECT DEPOSITION WITH APCVD

The rapid thermal direct deposition of micro-crystalline silicon (μc-Si) layers by atmospheric pressure chemical vapour deposition (APCVD) can be done on different intermediate layers and on various substrates. The deposition is done at temperatures between 850 °C and 1150 °C. A deposition rate of 1.6 μm/min has been achieved using standard process conditions. The microcrystalline structure changes depending on the deposition temperature and the layer thickness. Electron backscatter diffraction measurements show grain sizes of 0.5-10.0 μm with a columnar structure. The doping concentration depending on cell concept and layer thickness can be adjusted from 1 x 10 cm to 1 x 10 cm using diborane and from 1 x 10 cm to 1 x 10 cm using phosphine. Based on these process parameters and material properties the μc-Si layers have been simulated and optimised for two different solar cell concepts featuring different metallisation schemes and a comparison between epitaxial μc-Si emitter, diffused POCl3 emitter, and plasma enhanced chemical vapour deposition (PECVD) deposited a-Si heterojunction solar cells.