Spectroscopic analysis reveals that quasi donor-acceptor pair density correlates with open-circuit voltage and fill factor in Cu2ZnSnS4 solar cells, highlighting defects limiting device efficiency.
We examined the 4 K photoluminescence spectra of over a dozen Cu2ZnSnS4 films and eight devices. We show that samples deficient in zinc show on average a higher quasi donor-acceptor pair (QDAP) density. However, the QDAP density in samples with the same metal composition also varies widely. Devices prepared with similar metal compositions show different open-circuit voltages and fill factors. These metrics are correlated with the concentration of QDAPs in the absorbers. One additional device with insufficient zinc showed the empirically observed low-efficiency expected for this composition. This sample also showed the highest quasi donor-acceptor pair density of all the devices measured.
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Gershon et al. (2013) studied this question.