The Irresistible Charm of a Simple Current Flow Pattern – 25% with a Solar Cell Featuring a Full-Area Back Contact

Screen-printed Al-BSF silicon solar cells have dominated the PV market for decades. Their long-term success is based on a low-complexity cell architecture and a robust production sequence. The full-area rear contact allows a simple and effective one-dimensional current flow pattern in the base resulting in high fill factors. Some of the successor technologies of this simple but yet successful cell architecture, i.e. PERL and IBC solar cells, have a significantly higher process and pattern complexity. This presentation discusses a cell structure with an architecture very similar to the classical Al-BSF solar cell but with a higher efficiency potential. This is achieved by substituting the full-area doped back surface region by a passivated contact scheme consisting of a tunnel oxide covered by a heavily doped silicon film, called TOPCon. The current champion efficiency of 24.9% (Voc = 719 mV) on n-type silicon shows that this structure has a high potential while keeping the process effort low and the current flow pattern simple. The very high fill factor of 83.4% results from both, the very low recombination and transport losses caused by this contact scheme. This presentation will give a detailed overview on the ongoing improvement and up-scaling of the TOPCon technology.