Applications of time-resolved photoluminescence for characterizing silicon photovoltaic materials

Abstract

Heavily-doped, amorphous and polycrystalline silicon (poly-Si) layers play important roles in silicon solar cell fabrication and performance. Here we demonstrate applications of time-resolved photoluminescence decay to measure recombination lifetimes in such regions, which are generally below 1 µs, and difficult to measure with other techniques. Firstly, we demonstrate the measurement of Auger lifetimes in uniformly heavily-doped silicon wafers, and show the impact of surface recombination in samples with phosphorus or boron doping concentrations below 1 × 1019 cm−3. We also assess the possible impact of high concentrations of iron contamination on the extraction of such Auger lifetimes. We then report recombination lifetimes measured in thin deposited intrinsic amorphous silicon films, and heavily-doped poly-Si films, as commonly used in passivating contact structures. Interestingly, recombination lifetimes in intrinsic amorphous silicon films can be significantly enhanced by a hydrogenation process. By contrast, recombination lifetimes in heavily-doped poly-Si films vary with different doping profiles for samples fabricated with different deposition techniques, but are not improved by hydrogenation.