p-Layer bandgap engineering for high efficiency thin film silicon solar cells

Spectroscopic ellipsometry (SE), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and optical transmittance measurements were used to study and establish a correlation between the open-circuit voltage (V-oc) of solar cells and the p-layer optical band gap (E-p). It is found that the ellipsometry measurement can be used as an inline non-destructive diagnostic tool for p-layer deposition in commercial operation. The analysis of ellipsometric spectra, together with the optical transmittance data, shows that the best p-layer appears to be very fine nanocrystallites with an E-p 1.95 eV. HRTEM measurements reveal that the best p-layer is composed of nanocrystallites similar to 9 nm in size. It is also found that the p-layer exhibits very good transmittance, as high as similar to 91.6% at similar to 650 nm. These results have guided us to achieve high V-oc value 1.03 V for thin film silicon based single junction solar cell. (C) 2015 Elsevier Ltd. All rights reserved.