Record high 18.6% efficient solar cell on HEM multicrystalline material

Solar cells with efficiencies as high as 18.6% (1 cm² area) have been achieved by a process which involves impurity gettering and effective back surface passivation on 0.65 Ω-cm multicrystalline silicon (mc-Si) grown by the heat exchanger method (HEM). This represents the highest reported solar cell efficiency on mc-Si to date. PCD analysis revealed that the bulk lifetime (τ_b ) in HEM samples after phosphorus gettering can be as high as 135 μs. This increases the impact of the back surface recombination velocity (S_b) on the solar cell performance. By incorporating a deeper aluminum BSF, the S_b for solar cells in this study was lowered from 10000 cm/s to 2000 cm/s on HEM mc-Si. This combination of high τ_b and moderately low S_b resulted in the record high efficiency mc-Si solar cell. Model calculations indicate that lowering S_b further can raise the efficiency of untextured HEM mc-Si solar cells above 19.0%, thus closing the efficiency gap between good quality, untextured single crystal and mc-Si solar cells