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 S-eff 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 S-eff. Laser doping resulted in highly doped regions in the silicon with a sheet resistance of below 20 Omega/sq and surface doping concentrations close to 1 x 10(20) cm(-3). Accordingly, calculations showed that the saturation current density at the laser doped areas can be as low as 900 fA/cm(2) for line-shaped contact structures.