Optical and Electrical Improvement of Rear Side ITO for Heterojunction Back Contact Solar Cells

29th European Photovoltaic Solar Energy Conference and Exhibition; 1024-1027
In this paper, the electrical and optical characteristics of the Indium-Doped Tin Oxide (ITO) are tuned in order to design an ITO-based spacer between the a-Si:H and the metal contact suited for Amorphous / Crystalline Heterojunction interdigitated Back Contact Solar Cells (a-Si:H / c-Si HJ i-BC). ITO carrier concentration, mobility, resistivity, extinction coefficient, and work function, as well as the ITO / a-Si:H specific contact resistances are evaluated as a function of O2 relative flow rate during ITO deposition. An ITO having carrier concentration of 4.5x1019 cm-3, mobility of 20.2 cm2/(V.s) and resistivity of 6.24 mΩ.cm is found to be an optimum leading to ITO / a-Si:H(p/i) and ITO / a-Si:H(n/i) specific contact resistances values of 0.6 Ω.cm2 and 0.1 Ω.cm2 respectively and a RS reflectance of 58% at 1200nm when integrated in Silver / ITO / a-Si:H / c-Si(textured) test structures.