Study of Double Layer Indium Tin Oxide in Silicon Hetero-Junction Solar Cells.

In this literature, we discussed the effect of anti-reflection coating of silicon heterojunction (SHJ) solar cells with different characteristics of double layered indium tin oxide (ITO/ITO) structure. Firstly, the OPAL 2 simulation was performed to optimize the values of the photo generation-current density of ITO/ITO/Si device structures. Afterwards, experimental work was conducted by depositing ITO on the SHJ solar cell to analyze the anti-reflection coating effect. ITO was deposited on the SHJ solar cell for 90 to 180 seconds by varying the oxygen flow rate. The highest short-circuit current density of 39.25 mA/cm² was obtained when ITO was deposited for 150 seconds, which was higher than the short-circuit current density of non-deposited cell of ITO (38 mA/cm²). The efficiency of the SHJ solar cell increased by about 2% after additional ITO deposition to 20.75%, which was due to the improvement of short-circuit current density by ITO deposition. The double layer ITO helped to improve the efficiency of SHJ solar cell by increasing light absorption in a silicon wafer.

Improvement of Ohmic Contact Between the Indium Tin Oxide and Copper-Plated Contact of Solar Cells by Using the Cu-Sn Alloy Film.

Copper plating has been considered as a future metallization technique to reduce metal contact area and material cost in silicon heterojunction (SHJ) solar cells. In this paper, a Cu-Sn alloy film is used as a seed layer material on an indium tin oxide (ITO) layer with the goal to enhance contact resistivity between the seed and ITO layer. The contact resistivity between the seed layer and ITO is an important parameter because low contact resistivity is required for the high fill factor of the solar cells. In addition, it was confirmed that tin diffusion to ITO can affect contact resistivity by annealing samples having a Cu-Sn seed layer. Contact resistivity values of the samples were extracted by using transfer length method (TLM). Atomic percentage of tin in the Cu-Sn film was measured by the energy dispersive spectrometer (EDS). Also, tape tests were carried out to simply confirm the adhesion of contacts with the Cu-Sn seed layer.