Insights into Recombination Processes from Light Intensity–Dependent Open-Circuit Voltages and Ideality Factors in Planar Perovskite Solar Cells
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Author list: Thongprong N., Supasai T., Li Y., Tang I.-M., Rujisamphan N.
Publisher: Wiley-VCH Verlag
Publication year: 2020
Volume number: 8
Issue number: 5
ISSN: 2194-4288
eISSN: 2194-4296
Languages: English-Great Britain (EN-GB)
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Abstract
To analyze the dominant recombination, researchers often consider the diode ideality factor (nid), determined from the fitting of a semi-log plot of light intensity–dependent open-circuit voltage (Voc(lnI/I0)) to a linear dependence. This value is called “nid,Voc”. Theoretically, nid is the exponential dependence factor in the recombination rate function of the split of quasi-Fermi levels. This nid is called “nid,C”. Herein, correlations between nid,Voc, nid,C, and the dominant recombination are reconsidered using a validated numerical drift–diffusion model and a diode current analysis in perovskite solar cell devices having accumulations of charged defects near the carrier transporting interfaces. It is found that the interplay between the recombination processes affects the linearity of the Voc(lnI/I0) plots. Devices having a single dominant recombination process exhibit Voc(lnI/I0) plots that appear to be linear, resulting in nid,Voc ≈ nid,C of the dominant recombination. Conversely, bends in the Voc(lnI/I0) curves indicate that different (multiple) recombination mechanisms dominate at different light intensities, so nid,Voc is an effective nid of the total diode current whose value is not consistent with any nid,C values. This work provides more understanding of nid and how to interpret a Voc(lnI/I0) curve more correctly for the insights into recombination mechanisms. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Keywords
carrier recombination, diode currents, drift–diffusion modeling, ideality factors
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