Publication of joint results from cooperation betweeen IMEC Leuven, Shanghai Institute of Microsyste
Results of joint research from cooperation between IMEC Leuven, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences and Suntech R&D Australia were published in Solar Energy Materials and Solar Cells, 2014, Vol 122, pages 31-39, doi: 10.1016/j.solmat.2013.11.017, see http://www.sciencedirect.com/science/article/pii/S0927024813006016.
The hydrogen plasma passivation of thin film polycrystalline silicon (pc-Si) was investigated in conjunction with plasma texturing process to make efficient heterojunction solar cells. The pc-Si layers were first treated using direct and remote hydrogen plasma technologies. The heterojunction solar cells were then fabricated by subsequent deposition of i/n+ a-Si:H. Hydrogenation at high temperature (610 °C) results in enhanced dissolution and diffusion of hydrogen in pc-Si by a factor of about 3 and 4, respectively, in comparison with those at low temperature (420 °C). The hydrogen atoms in the pc-Si layer mainly bond to the silicon dangling bonds and form complexes with dopant atoms. In addition, platelets defects are generated by the hydrogen plasma in the sub-surface region of pc-Si hydrogenated at 420 °C and cause higher saturation current in the space charge region whilst they form in the region deeper than 1 ?m at 610 °C. Removal of the platelets using SF6/N2O plasma post-texturing after low-temperature hydrogenation not only enhances the short circuit current but also improves the open circuit voltage and the fill factor simultaneously. Combining plasma pre-texturing with high-temperature hydrogenation, the best 2 µm-thick pc-Si heterojunction solar cell reaches an efficiency of 8.54%.