Novel MWT cell design on monocrystalline silicon wafers

On multicrystalline silicon wafers the "Metal Wrap Through" (MWT) concept is a well established cell design. Some cells are available on the market or were announced to be available soon. Using this wafer material a MWT design can improve the cell efficiency by up to 0.6 % abs. However, on monocrystalline wafers the MWT concept faces additional challenges like reduced yield by breakage and additional electrical losses. The first one is due to the laser grooves which are needed for the isolation of emitter and base areas on the back side and extend across the whole wafer forming predetermined breaking lines in our standard MWT design. The electrical losses are due to an increased series resistance because of lateral currents above the back sided emitter busbars and to higher j02 losses because of the additional laser isolation. In this work we show concepts and technologies designed to overcome these disadvantages and to reduce the monocrystalline specific efficiency losses of the MWT concept.