Development and characterization of AlOx/SiNx :B layer systems for surface passivation and local laser doping

This work aims to improve the rear-side properties of p-type monocrystalline silicon solar cells by using the passivated emitter and rear locally diffused (PERL) solar cell concept. To realize the rear side structure, the so-called PassDop approach was used combining both surface passivation and local doping. The concept utilizes a multifunctional, doped AlOx/SiNx:B layer stack; the localized structuring is achieved by local contact opening and doping by a laser process. Using AlOx/SiNx:B PassDop layers, an outstanding effective surface recombination velocity Seff of less than 4 cm/s was achieved after firing at the passivated area. The boron concentration in the PassDop layers did not show any significant influence on Seff. Laser doping resulted in highly doped regions in the silicon with a sheet resistance of below 20 O/sq and surface doping concentrations close to 1 × 1020 cm-3. Accordingly, calculations showed that the saturation current density at the laser doped areas can be as low as 900 fA/cm2 for line-shaped contact structures.