Schematic cross-sections of and solar cells fabricated in this study.
(a) Total and diffuse transmissivity spectra of flat , Asahi-U, and textured ZnO on glass. (b) Total and diffuse reflectivity spectra of flat glass, Asahi-U, and textured ZnO substrates covered with Ag and 40-nm-thick ZnO:Ga layers. of the flat and Asahi-U substrates were measured without a protective ZnO layer. This coating reduces roughly at 0.5% in the range of 450–1200 nm.
Cross-sectional SEM images of solar cells grown on (a) and (b) flat, (c) and (d) Asahi-U, and (e) and (f) textured ZnO substrates. The samples in (a), (c), and (e) have flat front surfaces obtained by CMP.
Surface roughness and solar cell parameters of and cells (samples A–L): rms roughness of front and rear surfaces, , , , , and . The arrows indicate cells with flat surfaces obtained by CMP.
J–V curves of solar cells with and without polishing (samples I–L).
(a) Abs and (b) EQE of solar cells grown on flat and moderately textured substrates with and without rear surface polishing.
, , and in NIR region for solar cells grown on three different substrates with and without rear surface polishing.
(a) Abs and (b) EQE of solar cells grown on flat and moderately textured substrates with and without front surface polishing.
, , and in NIR region for solar cells grown on three different substrates with and without front surface polishing.
in NIR region for and cells.
Difference in EQEs of cells with thin and thick ITO layers used as front TCO layer. Here, we define .
(a) Absorption coefficients of and ZnO:Ga with carrier density of and carrier mobility of (Ref. 36) and (b) absorption spectra at BSRs in and solar cells.
of the (samples D and F) and (samples J and L) solar cells plotted as a function of wavelength. The lines show the expected contributions from the front TCO layer (, dotted line) and BSR (, dashed line) and their sum (, solid line). Here, the fitting parameters and are equal to and , respectively.
Solar cell samples fabricated in this study.
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