CuIn(Se1−xTex)2 solar cells with tunable narrow-bandgap for bottom cell application in multijunction photovoltaic devices

Narrow-bandgap CuIn(Se1-x,Tex)2–based solar cells for bottom cell application in multijunction photovoltaic devices were developed and characterized. Compact and well crystallized 2 μm films are obtained by single-stage coevaporation process on Mo-coated soda lime glass. Narrow bandgaps ranging from 0.98 eV to 0.88 eV were measured depending on the Te content of the films. The solar cells were characterized by current density versus voltage under standard AM 1.5 illumination and under a wider bandgap CIGSe/SLG filter. The same methodology was applied for the spectral response analysis, and the beneficial effect of the narrow bandgap in the multijunction configuration was remarkable in the low energy spectral region. Efficiencies higher than 7% under AM 1.5 illumination, and close to 2% in the multijunction-like configuration, were achieved.