Exciton spectra, valence band splitting, and energy band structure of CuGaXIn1−XS2 and CuGaXIn1−XSe2 crystals

Energy Generation: Solar Energy

“…In Figure 2.10, we see that-although a shifted mesh of 1000 k points is not sufficiently dense to smooth out the curve due to the strong dispersion of the lowest conduction statethe experimental onset at about 2.55 eV and the peak at about 3.8 eV are well reproduced in the BSE calculation [98]. At the absorption edge, the estimate of the excitonic binding energy of about 0.1 eV is also consistent with experimental data [130].…”

Birefringence of CuGa2S4 crystals

“…One can conclude from these data that the energetic interval between the V 1 and V 2 bands equals 83 meV, and the interval between V 2 and V 3 bands is of 17 meV. These results suggest that the energetic intervals between the valence bands at room temperature and at 10 K are different [15][16][17][18][19][20]. Apart from that, the symmetry of the V 2 and V 3 bands becomes Г 7 and Г 6 , respectively.…”

“…The isotropic point λ o1 revealed at 2.5012 eV corresponds to the energy of the longitudinal exciton Г 4 . It was shown previously [16][17][18][19][20][21][22] that an energy transfer occurs between the waves of the excitonic polaritons Г 4 and Г 5 in the neighborhood of resonances, i.e. at these wavelengths.…”

“…The upper valence band is of the Γ 7 V symmetry and the lower conduction band is of Γ 6 C symmetry. The excitonic states are formed when the condition ℏω = E C − E V is fulfilled [16][17][18][19][20][21][22].…”

“…The gradual change of the refractive index in the E⊥c polarization is due to the Г 6 -Г 6 transitions. Three excitonic series A, B and C are revealed in the CuGaS 2 crystals [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. The interaction of electrons from the conduction band Г 6 and holes from the valence band Г 6 is determined by the product of irreducible representations Г 1 × Г 6 × Г 7 = Г 3 + Г 4 + Г 5 .…”