Zheng, P.Rougieux, F. E.Samundsett, C.Yang, XinboWan, YimaoDegoulange, J.Einhaus, R.Rivat, P.Macdonald, D.2016-09-290003-6951http://hdl.handle.net/1885/109105We present solar cells fabricated with n-type Czochralski–silicon wafers grown with strongly compensated 100% upgraded metallurgical-grade feedstock, with efficiencies above 20%. The cells have a passivated boron-diffused front surface, and a rear locally phosphorus-diffused structure fabricated using an etch-back process. The local heavy phosphorus diffusion on the rear helps to maintain a high bulk lifetime in the substrates via phosphorus gettering, whilst also reducing recombination under the rear-side metal contacts. The independently measured results yield a peak efficiency of 20.9% for the best upgraded metallurgical-grade silicon cell and 21.9% for a control device made with electronic-grade float-zone silicon. The presence of boron-oxygen related defects in the cells is also investigated, and we confirm that these defects can be partially deactivated permanently by annealing under illumination.This work was supported by the Australian Renewable Energy Agency (ARENA) through the Australian Center for Advanced Photovoltaics (ACAP), Project RND009, and their Postdoctoral Fellowships program. D.M. acknowledges the support from the Australian Research Council through the Future Fellowships program.© 2016 AIP Publishing LLC.2016-03-2210.1063/1.4944788