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DOE OSTI · 1726049

Back-Surface Passivation of CdTe Solar Cells Using Solution-Processed Oxidized Aluminum

Alfadhili, Fadhil K.·Phillips, Adam B.·Subedi, Kamala Khanal·Perkins, Craig L.·Halaoui, Adam I.·Jamarkattel, Manoj K.·Anwar, Bhuiyan M.·Liyanage, Geethika K.·Li, Deng-Bing·Grice, Corey R.·Yan, Yanfa·Ellingson, Randy J.·Heben, Michael J.
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Abstract

Although back-surface passivation plays an important role in high-efficiency photovoltaics, it has not yet been definitively demonstrated for CdTe. Here, we present a solution-based process, which achieves passivation and improved electrical performance when very small amounts of oxidized Al 3+ species are deposited at the back surface of CdTe devices. The open circuit voltage (V oc ) is increased and the fill factor (FF) and photoconversion efficiency (PCE) are optimized when the total amount added corresponds to ~1 monolayer, suggesting that the passivation is surface specific. Addition of further Al 3+ species, present in a sparse alumina-like layer, causes the FF and PCE to drop as the interface layer becomes blocking to current flow. The optimized deposit increases the average baseline PCE for both Cu-free devices and devices where Cu is present as a dopant. The greatest improvement is found when the Al 3+ species are deposited prior to the CdCl 2 activation step and Cu is employed. In this case, the best-cell efficiency was improved from 12.6 to 14.4%. Furthermore, time-resolved photoluminescence measurements at the back surface and quantum efficiency measurements performed at the maximum power point indicate that the performance enhancement is due to a reduction in the interface recombination current at the back surface.

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14 SOLAR ENERGYAluminum oxideBack contactCdTeCdTe solar cellsaluminaback contactinterface passivationsolution processed

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Alfadhili, Fadhil K., Phillips, Adam B., Subedi, Kamala Khanal, Perkins, Craig L., Halaoui, Adam I., Jamarkattel, Manoj K., Anwar, Bhuiyan M., Liyanage, Geethika K., Li, Deng-Bing, Grice, Corey R., Yan, Yanfa, Ellingson, Randy J., Heben, Michael J.. 2020-11-04. Back-Surface Passivation of CdTe Solar Cells Using Solution-Processed Oxidized Aluminum. https://doi.org/10.1021/acsami.0c12800

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