Enhancing the optical and dielectric constants of Cu-Ge-S films for solar cell windows

This work concerns the optical characteristics of ternary Cu x Ge 25 S 75-x (0.0 <x ≤ 12.0 at.%.) films. The transmission spectra (T(λ)) of Cu x Ge 25 S 75-x (CGS) films display interference fringes with low absorption coefficients (α) in the transparent region of 0.5–2.5 μm. The film refractive index (n) and optical density (x) have been precisely determined without any dependence on the film thickness using only the lower envelope of the measured film transmittance (T m ). The film thickness (t) is determined using the interference fringe main equation (2 nt = mλ where m is the order number). The phenomenon of absorption edge redshift is a fascinating occurrence that can be attributed to variations in the concentrations of copper (Cu) contents. ( α h ν ) 1 / 2 vs. h ν plots are used to compute bandgap energy (E g ) and the band tail parameter (B). Indicators of the Cu addition effect on polarization and electromagnetic wave interactions include the complex dielectric constant ( ε ∗), optical conductivity ( σ ∗ ), and the dielectric loss factor (tan δ). The effects of Cu contents on charge carrier mobility and energy losses are emphasized by the energy loss functions (VELF and SELF) and electric modulus (M∗). Moreover, relaxation mechanisms and impedance variations are investigated, producing distinctive Nyquist diagrams . This thorough characterization improves our comprehension of CGS films for possible optoelectronic applications .