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The SIMS depth profiles of Mo, Cu, Zn, Sn, and Se (lines) are shown for the SLG device. Those for the E2k and SLG + NaF devices are similar. Also shown are the Na profiles (lines with symbols) for devices with all three Na variations. The symbols are used for identification purpose only and do not represent all the data points, which are represented by the lines.
The light (dashed lines with symbols) and dark (solid lines with symbols) current-voltage characteristics show that the SLG and SLG + NaF devices exhibit higher efficiency, VOC, and FF, but smaller JSC than the E2k device. The SLG + NaF device exhibits higher efficiency, VOC , FF, and JSC than the SLG device. Quantum efficiency spectra in the inset show that the E2k device has the best long-wavelength response, followed by the SLG + NaF device, and then the SLG device.
(a) The Arrhenius plots constructed from the AS and DLTS measurements are used to extract the activation energies of the deep levels by line fitting. (b) The densities of states nearby the deep levels are calculated from the AS (solid lines with symbols, left axis) and DLTS (dashed lines with symbols, right axis) data. The same pre-exponential factor is used for both the E2k and SLG devices when calculating the density of states from the DLTS data. The arrows indicate the temperatures at which the features are seen in the raw DLTS spectra taken with a rate window of 100 ms in E2k and SLG devices.
TRPL decays for samples E2k (red dots), SLG (blue dots), and SLG + NaF (green dots). A vertical offset is used for clarity. Excitation intensity was 0.57 W cm−2 (average laser power 0.14 mW, laser beam diameter 0.17 mm, injection ≈1017 cm−3). Solid lines show fits to the data obtained assuming two-exponential decay model and de-convoluting the instrumental response (shown in black). Inset shows intensity dependence for the second decay component, τ2.
Summary of typical device performance and material properties.
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