SEM images (cross sections, 65° tilt) of (a) standard nonetched (2500 nm) as-deposited CIGSe absorber; and etched CIGSe surfaces after (b) 30 s; (c) 2 min; and (d) 4 min of etching.
RMS roughness of the CIGSe surface versus etching time of the films.
High energy resolution (a) Cu 2p, (b) Ga 2p, (c) In 3d, and (d) Se 3d XPS spectra acquired for the CIGSe surface before the etch treatment (gray line) and after 4 min of etching (black line). XPS spectra are normalized in intensity for more clarity.
(a) X-ray diffraction patterns; (b) Raman spectra of as deposited CIGSe absorber and 4 min etch CIGSe absorbers.
Evolution of the total reflectivity of the (a) bare CIGSe surface and (b) the completed solar cells stack with different CIGSe roughness.
Photovoltaic parameters from J(V) characterization for CIGSe solar cells as function of the surface roughness of the CIGSe absorber: (a) Efficiency and short circuit current (Jsc); (b) open circuit voltage (Voc) and fill factor (FF).
(a) EQE for different etching times; (b): EQE ratio for different etching times.
IQE for different etching times; inset: fitting of the tail of the IQE for a smooth CIGSe sample.
Schematic representation of the space charge region for a flat and a rough p-n interface.
Simulated IQE curves where the space charge region W and the minority carriers diffusion length Ln are varied while keeping W + Ln at a constant value Leff.
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