Stable Reverse Bias or Integrated Bypass Diode in HIP-MWT+ Solar Cells Based on Different Industrial Rear Passivation
The Metal Wrap Through+ (HIP-MWT+) solar cell is based on the PERC concept but features two additional electrical contacts, namely the Schottky contact between p-type Si bulk and Ag n-contact and the metal-insulator-semiconductor (MIS) contact on the rear side of the cell below the n-contact pads. To prevent hotspots under reverse bias, both contacts shall either restrict current flow or allow a homogenous current flow at low voltage. In this work we present both options. First the stable reverse bias characteristics up to - 15 V with a MIS contact using industrially manufactured SiON passivation and second, an integrated by-pass diode using AlOX as insulator in the passivation stack allowing current flows at approximately Vrev = - 3.5 V depending on the chosen screen-print paste. The examined Schottky contacts break down at around Vrev = - 2.5 V. Reverse bias testing of the cells proof a solid performance of the cells under reverse bias and an average conversion efficiency of = 21.2 % (AlOX) and = 20.7 % (SiON), respectively.