Electronic band alignment at CuGaS2 chalcopyrite interfaces

Abstract

Cu-chalcopyrite semiconductors are commonly used as light absorbing materials on solar cell devices. The study of the heterointerfaces between the absorbent and the contact materials is crucial to understand their operation. In this study, band alignments of the heterojunctions between CuGaS 2 chalcopyrite and different semiconductors have been theoretically obtained using density functional theory and more advanced techniques. Band alignments have been determined using the average electrostatic potential as reference level. We have found that the strain in the heterointerfaces plays an important role in the electronic properties of the semiconductors employed here. In this work CuAlSe 2 /CuGaS 2 and CuGaS 2 /ZnSe heterointerfaces show band alignments where holes and electrons are selectively transferred through the respective heterojunctions to the external contacts. This condition is necessary for their application on photovoltaic devices.

Tight-binding electronic band structure and surface states of Cu-chalcopyrite semiconductors

“…Using a self consisted GW scheme based on Hedin's Coulomb hole and screened exchange (scCOHSEX) followed by a perturbative G 0 W 0 step, Aguilera et al, reported an energy gap of 2.65 eV for CuGaS 2 , in very good agreement with the experimental value [20]. Recently, we have done ab-initio DFT theoretical calculations using a modified screened hybrid Heyd-Scuseria-Ernzerhof functional (HSE06) to improve the GGA approximation, and we have obtained a band gap of 2.43 eV, which reproduces excellently the experimental value [21].…”

“…Recently, we have carried out ab-initio calculations of the structural and electronic properties of these materials, and the results obtained were reported in reference [21]. From the reference of Castellanos et al [21], we observe that the obtained values for the band gap is 2.43 eV for the CuGaS 2 , and 2.65 eV for the CuAlSe 2 .…”

“…Recently, we have carried out ab-initio calculations of the structural and electronic properties of these materials, and the results obtained were reported in reference [21]. From the reference of Castellanos et al [21], we observe that the obtained values for the band gap is 2.43 eV for the CuGaS 2 , and 2.65 eV for the CuAlSe 2 . Unfortunately if we introduce the values of the TB parameters obtained from the Harrison's rule, it is not possible to reproduce correctly, neither the experimental values, nor those obtained from first-principle calculations.…”

“…1.36 column of table 4 we show the value of the band gap parameter obtained using the Harrison rule; the third column corresponds to the values obtained from first principles according to the approximations reported in the reference [21]; the fourth column contains the experimental reported values; whereas the last column corresponds the results of the present work.…”

“…Atomic positions in the CuGaS 2 chalcopyrite. The values of the distortion parameter η=c/2a, and the anion displacement u (in units of a), used in this work were 0.996 and 0.2532 respectively [21].…”