CuIn1−xGaxSe2 solar cells with thin absorbers analyzed by spectroscopic ellipsometry: Insights into quantum efficiency and optical/collection losses

CuIn
_1-x
Ga
_x
Se
₂
(CIGS) solar cells fabricated with thin absorber layers were studied by spectroscopic ellipsometry to deduce their multilayer structures, which enable quantum efficiency (QE) simulations. For all cells with thin absorbers studied here, the measured QE spectra are reduced relative to those simulated assuming 100% carrier collection in the active CIGS-containing layers. Thus, the measured QE spectra can be understood in terms of both optical and carrier collection losses, the latter for electrons and holes generated near the Mo contacts. Collection losses are negligible for standard (2.2 μm) absorbers.