10 × 10 cm2 Hit Solar Cells Contacted with Lead-Free Electrical Conductive Adhesives to Solar Cell Interconnectors

In the present study we have investigated the optical and electrical properties of 10times10 cm
²
HIT solar cells with evaporated Cr/Ag grids. Contacts were done with low temperature lead-free electrically conductive adhesives to standard solar cell interconnector tabs (IT). Compared to solder joints conductive adhesives have the advantage of lower contact formation temperature with reasonable low contact resistances (less than 1 mOmegacm
²
). ITs glued directly on ITO are not long term stable if the applied pressure during manufacturing is too low. Their contact resistance increases by about three to four orders of magnitude after 50 temperature cycles (-40degC/85degC). Thin Ag layers beneath the glue avoid contact degradation. Depending on the contact gluing process parameters (temperature, time, pressure and glue material) especially on textured substrates the polymer constituent of the conductive adhesive can bleed out into the solar cell light exposed area and provoke a higher optical reflection