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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sr(ZnSn)2 by Materials Project

SrZn2Sn2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Sr is bonded in a 4-coordinate geometry to eight Zn and eight Sn atoms. There are a spread of Sr–Zn bond distances ranging from 3.53–3.78 Å. There are a spread of Sr–Sn bond distances ranging from 3.51–3.77 Å. There are two inequivalent Zn sites. In the first Zn site, Zn is bonded in a 9-coordinate geometry to four equivalent Sr and five Sn atoms. There are a spread of Zn–Sn bond distances ranging from 2.65–2.85 Å. In the second Zn site, Zn is bonded in a 4-coordinate geometry to four equivalent Sr and four equivalent Sn atoms. There are a spread of Zn–Sn bond distances ranging from 2.75–2.81 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Sr and five Zn atoms. In the second Sn site, Sn is bonded to four equivalent Sr and four equivalent Zn atoms to form a mixture of distorted edge and face-sharing SnSr4Zn4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Alkali element (Li, Na, K, and Rb) doping of Cu 2 BaGe 1– x Sn x Se 4 films

Cu 2 BaGe 1–x Sn x Se 4 (CBGTSe) represents an exemplary system within the I 2 –II–IV–X 4 (I = Ag, Cu; II = Sr, Ba; IV = Ge, Sn; X = S, Se) family, which has been introduced to target suppressing the formation of anti-site defects and associated defect clusters within the analogous kesterite Cu 2 ZnSn(S,Se) 4 . Previous studies on CBGTSe films showed relatively low hole carrier densities (<10 13 cm –3 ), which may limit their corresponding application as active layers within photovoltaic, thermoelectric, and optoelectronic devices. In the current study, we explore the incorporation of alkali elements (Li, Na, K, and Rb) into CBGTSe films as prospective dopants to address the low hole carrier density and to allow for property tunability. First, incorporation of Na-, K-, and Rb-dopants noticeably increases the average grain sizes for CBGTSe films, while the Li-dopant has relatively limited impact. In addition, the alkali-dopants lead to a 1 to 3 orders of magnitude increase in hole carrier density (up to 10 15 cm –3 is achieved using K doping, corresponding to the alkali element yielding the highest doping efficiency). Here, the alkali-doped films show slightly lower minority carrier lifetimes and carrier mobility values than the non-doped samples, and these values are found to follow an approximate universal dependence with carrier density (also considering data derived from other previously explored vacuum-deposited I 2 –II–IV–X 4 chalcogenide films). As alkali-doping can significantly increase carrier densities, alkali elements can be considered useful p-type dopants for CBGTSe, as well as prospectively for other analogous I 2 –II–IV–X 4 systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗