Short- and Long-Range Cation Disorder in (Ag_xCu_1–x)₂ZnSnSe₄ Kesterites

Abstract

Understanding the nature of and controlling the cation disorder in kesterite-based absorber materials remain a crucial challenge for improving their photovoltaic (PV) performances. Herein, the combination of neutron diffraction and synchrotron-based X-ray absorption techniques was implemented to investigate the relationships among cation disorder, defect concentration, overall long-range crystallographic order, and local atomic-scale structure for (Ag x Cu 1−x ) 2 ZnSnSe 4 (ACZTSe) material. The joint Rietveld refinement technique was used to directly reveal the effect of cation substitution and quantify the concentration of defects in Ag-alloyed stoichiometric and nonstoichiometric Cu 2 ZnSnSe 4 (CZTSe). The results showed that 10%-Ag-alloyed nonstoichiometric ACZTSe had the lowest concentration of detrimental antisite Cu Zn defects (∼8 × 10 19 defects per cm −3 ), which was two times lower than pristine and five times lower than the stoichiometric compositions. Moreover, Ag incorporation maintained the concentrations of beneficial Cu vacancies (V Cu ) and antisite Zn Cu defects to >2 × 10 20 defects per cm −3 . X-ray absorption measurements were performed to verify the degree of disorder through the changes in bond length and coordination number. Therefore, the incorporation of Ag into the CZTSe lattice could control the distribution of antisite defects, in the form of short-and long-range site disorder. This study paves the way to systematically understand and further improve the properties of kesterite-based materials for different energy applications.

Oxygen-Incorporated Lithium-Rich Iron Sulfide Cathodes for Li-Ion Batteries with Boosted Material Stability and Electrochemical Performance

“…XANES spectroscopy of the S K edge in Li 2 FeS 1.8 O 0.2 showed the local electronic structure changes after oxygen incorporation into the lattice of Li 2 FeS 1.8 O 0.2 (Figure S4). The absorption features of the XANES spectrum are mainly influenced by unoccupied states in the conduction band, with only a minor influence from core-hole interactions. , Using ab initio-based MLIP to perform large-scale MD simulations, we obtained the pair correlation functions (PCFs) of Li–Li ions, denoted as g Li–Li ( r ), at different temperatures ranging from 300 to 500 K. As illustrated in Figure d, the first-coordination peak of the pristine Li 2 FeS 2 significantly decreases as the simulation temperature increases. In contrast, the first-coordination peak of the oxygen-incorporated sample displays much less sensitivity to the temperature variations.…”

Defects go green: using defects in nanomaterials for renewable energy and environmental sustainability

“…(Rice et al, 2014;Knowles et al, 2015;Fuhr et al, 2020a;Anand et al, 2020;Fuhr et al, 2020b). These large variations are atypical for QDs, and defect-free structures are atypical for covalently bonded multinary structures-especially those with large variations in stoichiometry (Alvarez-Garcia et al, 2000;Hahn et al, 2001;Paier et al, 2009;Ye et al, 2019;Vijay et al, 2021;Han et al, 2022;Quadir et al, 2022). Given these characteristics and the well-known tendency to form defects in the bulk CISeS phase (Ueng and Hwang, 1989;Ueng and Hwang, 1990;Alvarez-Garcia et al, 2000;Hahn et al, 2001), it is highly likely that defects are impacting the spectral properties in some way, and that regardless of the precise emission mechanism understanding synthesis-defect formation relationships for CISeS QDs could improve LSC performance.…”