Ultra‐Thin Bipoly Solar Cells With Front Selective n‐Type TOPCon and Rear Blanket p‐Type TOPCon Layers

This study investigates ultra‐thin silicon solar cells with polysilicon (poly‐Si) passivated contacts on both sides (biPoly cells). Low‐pressure chemical vapor deposition (LPCVD) was used for the deposition of front and rear poly‐Si layers along with a complete passivation structure. Patterning of the top poly‐Si layer was used to restrict it to the metal‐finger regions, thereby improving carrier lifetime and useful light absorption. A saw damage etching (SDE) process with varied time was used for thinning down the silicon (Si) substrates. The thinnest bendable cell achieved is 80 m thick, with an efficiency of 19.7%. Because cell mass per area approximately scales with silicon thickness, the efficiency‐to‐thickness ratio is a practical proxy for specific power in lightweight/flexible use‐cases. Our devices reach 0.25% per m, to our knowledge among the highest reported for TOPCon cells at comparable thickness. The results highlight the potential of selective biPoly passivated ultra‐thin silicon solar cells for high‐performance photovoltaic applications.