TCO layers for TOPCon based perovskite-silicon tandem solar cells: Process sequences and electrical losses

This work provides guidelines for hydrogenation and integration of sputtered transparent conductive oxides (TCO) in TOPCon-based bottom cells which is an essential aspects for the transition from Silicon single junction to Perovskite-Silicon tandem solar cells. A systematic comparison of different hydrogenation approaches including hydrogenation via sacrificial dielectric layers, remote plasma Hydrogen passivation and Hydrogen rich TCO layers, targeting low recombination and a potentially lean process sequence for both side or only front side TOPCon based bottom cells, is presented. For both side TOPCon based bottom solar cells, the process compatibility of n- and p-TOPCon is addressed, with a particular focus on process temperatures during hydrogenation and TCO sputter damage recovery. The passivation quality of p-TOPCon is evaluated for both textured and planar surfaces. Identified trade-offs between passivation quality and process complexity are discussed, as well as the interplay between passivation and contact resistivity. Based on this, both factors are assessed regarding their estimated impact on tandem solar cell efficiency and process recommendations are provided. Results indicate that lean process sequences, such as TCO:H based hydrogenation, can be effective for n-TOPCon and p-TOPCon on planar surface, while sacrificial dielectric layers remain necessary for textured p-TOPCon rear contacts to minimize efficiency losses.