Resistivity analysis on the enhancement of silicon heterojunction solar cells in light-thermal treatment

Enhancement of silicon heterojunction (SHJ) solar cells by light-thermal treatment has been analyzed in terms of their electrical resistivity changes. Three types of transmission line model (TLM) structures were prepared to analyze the changes of the solar cells in their Ag/ITO contact resistivity, and electron and hole transport resistivity respectively, in the light-thermal processes. The results showed that the contact resistivity of Ag/ITO increased by 88.5 m Omega cm2 and the transport performance improvement of holes is significantly better than that of electrons. Further examinations showed that the former was due to the deterioration of the ITO films, while the latter was due to the enhanced dark conductivity of doped a-Si:H layers and the different performance between (n)a-Si:H and (p)a-Si:H during the light-thermal process. A general efficiency gain of 0.3%abs was found for this batch of solar cells. An alternative batch of SHJ solar cells with better ITO films grown elsewhere, which did not deteriorate in the light-thermal process, was found to achieve 0.5%abs gain in efficiency by the same light- thermal process.