Comparison of Passivation Properties of Phosphorus and Boron Ex-Situ Doped Poly-Silicon on Oxide Layers

Passivating the contacts of crystalline silicon (c-Si) solar cells with a polycrystalline silicon layer (poly-Si) on a thin oxide (SiOx) film is an effective approach to minimize the recombination current at the metal/c-Si interface. Combined with an ex-situ doping step (POCl3 diffusion), this approach has become mainstream in PV market for TOPCon solar cells rear side passivation by poly-Si (P) / SiOx stacks. Beyond the optimization of n-type poly-Si / SiOx stacks, this study investigates the use of a BCl3 diffusion to form poly-Si (B) / SiOx stacks. Those p-type TOPCon stacks are of high interest both at short term to improve industrial TOPCon front surface passivation and for the development of double side passivated TOPCon bottom-cells for tandem applications. Thereafter are presented the doping profiles and passivation properties of both p and n-type ex-situ doped poly-Si / SiOx stacks deposited on polished and textured surfaces, as well as their stability toward firing.