Iron-incorporated chalcopyrite of an intermediate band for improving solar wide-spectrum absorption

The high efficiency chalcopyrite tandem cell with two solar absorbers of CuGaS₂ and CuInSe₂ remains difficult to be fabricated, but intermediate band chalcopyrite is practical to be developed. Herein, the Fe incorporation into the Ga site of chalcopyrite is successful to induce obvious solar multiband absorption. Three intermediate bands are evidenced by the UV–Vis–NIR absorption spectra, which is confirmed by first principle density functional theory (DFT) calculations. These intermediates bands improve solar energy conversion by absorbing more photons in several solar energy ranges including 2.21–1.48 eV, 1.48–0.73 eV, and around 0.57 eV to enhance solar thermal collection and photocatalytic degradation. The consistent nature of the intermediate bands suggested by theoretical analyses mainly are composed of the nondegenerate the e_g and t_2g states of Fe-3d orbitals.