Development and characterization of multifunctional PECVD SiNX:P layers for laser-doped selective emitters

We apply stacks of silicon nitride (SiNX) layers consisting of phosphorus-doped SiNX (SiNX:P) and undoped SiNX as first and second layer, on the front surface of p-type monocrystalline silicon passivated emitter and rear cells (PERC). The stack is deposited using plasma-enhanced chemical vapor deposition. These layer stacks provide excellent surface passivation and anti-reflection properties comparable to single undoped SiNX layers. A laser processing locally introduces the phosphorus dopants from the SiNX:P/SiNX layer stack into the silicon and locally removes the layer stack. Thereby, local highly doped areas with sheet resistances as low as Rsh ≈ 20 O/sq are obtained. We refer to this as the nPassDop approach, which provides local high doping and structuring of the anti-reflection coating in one process. The saturation current density of the laser processed areas is estimated to be as low as j0,laser ≈ 500 fA/cm2. First implementations for large-area p-type Cz-Si PERC cells with self-aligned NiCuAg plated front contacts yield an energy conversion efficiency of 19.6%.