Highly efficient all-screen-printed back-contact back-junction silicon solar cells with aluminum-alloyed emitter
All-screen-printed back-contact back-junction silicon solar cells with aluminum-alloyed emitter on n-type base material were fabricated and analyzed at Fraunhofer ISE PV-TEC. Three different process sequences are compared to each other. One process flow with shallow phosphorus profiles realizes cells with efficiencies of 19.7%. Using a long thermal oxidation, cells with deep driven-in phosphorus profiles (front and back surface field) were processed where solar cell efficiencies of 20.0% are realized. Both cell efficiencies are independently measured at Fraunhofer ISE CalLab on a designated area of 16.65 cm2. The specific contact resistivity of screen-printed and fired silver paste to silicon surfaces with different phosphorus profiles was determined in dependence of several firing conditions. The main developed features of the presented cell structure comprise the firing-stable front and rear passivation layers, the spiking-free passivation layer against aluminum and t he deep driven-in phosphorus profile that can be contacted by silver screen-printing paste in a firing step.