Innovative structures for thin film crystalline silicon solar cells to give high efficiencies from low quality silicon

The multilayer solar cell has been specifically designed with the aim to obtain high solar cell efficiency using low quality, thin film, polycrystalline silicon material. The structure consists of multiple p- and n-type silicon layers. This paper examines the tolerance of the cell design to a range of metallic impurities and grain boundaries using computer simulation. The modelled results indicate that the device can tolerate impurity concentrations up to 250 times greater than a conventional, thick solar cell. Further, the results indicate that the structure has excellent tolerance to grain boundaries present in bulk regions of the device. The simulations indicate that grain boundaries present in depletion regions will limit efficiencies considerably if the effective recombination velocity of the grain boundary approaches 10⁷ cm/s. This extreme case should be largely avoided utilizing grain boundary passivation techniques during device fabrication