Rapid Recombination by Cadmium Vacancies in CdTe

CdTe is currently the largest thin-film photovoltaic technology. Non-radiative electron–hole recombination reduces photovoltaic efficiencies from an ideal value of 32% to a current champion performance of 22%.  The cadmium vacancy is a prominent acceptor species in p-type CdTe; however, debate continues regarding its structural and electronic behaviour.

Using state-of-the-art ab-initio defect techniques, three TYC researchers finally reconcile theoretical predictions with experimental observations for this species, calculating a negative-U double-acceptor level, while also reproducing the hole-polaron of the -1 charge state.  They found that cadmium vacancies facilitate rapid charge-carrier recombination, reducing maximum power-conversion efficiency by over 5% for untreated CdTe—a consequence of tellurium dimerization, metastable structural arrangements, and anharmonic potential energy surfaces for carrier capture.



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