Effect of wet‐chemical substrate pretreatment on electronic interface properties and recombination losses of a ‐Si:H/c ‐Si and a ‐SiNx:H/c ‐Si hetero‐interfaces

Abstract

AbstractSurface charge, surface state density and interface recombination behavior on polished float zone (FZ) solar cell substrates were investigated after various wet‐chemical pre‐cleaning procedures and deposition of amorphous silicon (a‐Si:H) or silicon nitride (a‐SiNx:H). Applying surface photo voltage (SPV), microwave detected photo conductance decay (µW‐PCD) and transient microwave conduction (TRMC) measurements, electronic interface properties were monitored repeatedly during the preparation processes. As shown for an inverted a‐Si:H/c‐Si hetero‐junction structure, with front side passivation by a‐SiNx:H and a p‐type a‐Si:H emitter on the rear side, the effect of optimised wet‐chemical pre‐treatment can be preserved during the subsequent soft plasma enhanced chemical vapour deposition of a‐Si:H or a‐SiNx:H. This leads to hetero‐interfaces with low interface recombination velocities. These results were compared to previously reported findings, obtained on textured Czochralski (CZ) single crystalline substrates. a‐SiNx:H is known to result in a field effect passivation. Nevertheless a strong influence of wet‐chemical treatments on surface charge and recombination losses was observed on both flat and textured a‐SiNx:H/c‐Si interfaces. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)