Fig. 4: Electron beam-induced current and carrier density analysis.
From: Unveiling microscopic carrier loss mechanisms in 12% efficient Cu2ZnSnSe4 solar cells
a,b, Cross-sectional SEM image (a) and EBIC image (b) of a cleaved CZTSe device. The beam energy was 5 keV. c, Normalized EBIC Intensity (IEBIC,norm) profile (blue dots) along the dashed yellow arrows shown in a and b and the fitting with analytical model (red line). The space charge region (SCR) and QNR are separated with the vertical dashed lines. The fluctuation of the EBIC signal is induced by the rough morphology. The regions with protrusions show weak EBIC because of the higher reflection of electron beam, and vice versa. The EBIC signal at the SCR region is severely altered by the non-flat morphology, which may lead to a large error in fitting of depletion region width. The QNR region shows a relatively flat morphology and thus is used for fitting diffusion length in this region. d, Carrier density profiles measured with capacity voltage (CV) and drive-level capacity profile (DLCP) with junction area before (blue) and after (red) modification. NCV and NDLCP are apparent carrier densities measured by CV and DLCP, respectively. f is the modulation frequency used for the CV and DLCP measurements. εr is the relative dielectric constant of CZTSe. Aj is the junction area. The inset shows the plain view SEM image of a CZTSe absorber.
