Multinuclear (67Zn, 119Sn and 65Cu) NMR spectroscopy – an ideal technique to probe the cationic ordering in Cu2ZnSnS4 photovoltaic materials

Abstract

For the very first time, (67)Zn, (119)Sn and (65)Cu NMR investigations have been carried out on Cu2ZnSnS4 derivatives (CZTS) for photovoltaic applications. NMR spectroscopy is shown to be sensitive enough to probe the Cu/Zn disorder within the kesterite structure of the studied compounds. In addition, reference spectra of Cu2ZnSnS4 are provided, and experimental (67)Zn and (65)Cu parameters are compared with ab initio calculations.

Phase-transition-driven growth of compound semiconductor crystals from ordered metastable nanorods

“…We conclude that the complete kesterite formation with ordered Sn cation site occupation takes about 18 seconds, as marked by the third line in Fig. 2b and c. We note that the real-time data are not sensitive to Cu-Zn disorder resulting in so-called disordered kesterite [34][35][36] -which, however, is predicted to be less critical for the electronic structure of CZTS [33,34]. The evolution of grain growth is monitored by the broadening of the diffraction reflexes.…”

A low-temperature order-disorder transition in Cu2ZnSnS4 thin films

“…Order parameters are ideally obtained from diffraction methods, but standard X-ray techniques cannot distinguish Cu þ and Zn 2þ , and neutron diffraction is unsuitable for thin films. Nuclear Magnetic Resonance (NMR), which has also been shown to be sensitive to Cu-Zn disorder in CZTS powders, 12 has the same limitation. Therefore, we investigated the potential of Raman spectroscopy to assess Cu/Zn disorder.…”

“…14 We first considered two stoichiometric CZTS powder reference samples, described elsewhere. 12 The samples differed only in the rate of cooling from their synthesis temperature, 1020 K. Sample VS was slowly cooled, at a rate of 10 K/h, whilst sample VF was quenched in ice-water. NMR measurements showed that VS has a high level of order (although is not thought to be perfectly ordered), whilst VF is disordered.…”

Structural transitions of ordered kesterite-type Cu2ZnSnS4 under pressure

“…1). 8,9 This phase is structurally derived from the sphalerite-type structure by a doubling of the respective c-axis, resulting from alternating cationic (Cu/Sn or Cu/Zn) layers separated by sulfur anions. 10 Consequently, all of the cations are tetrahedrally coordinated with respect to the anions.…”

“…Even though the KS phase represents an ordered cationic arrangement, i.e., each cation occupies a unique Wyckoff site, cationic disorder is quite common in this material. 8,[11][12][13][14] Such a disorder can affect the photovoltaic properties of this system. For example, a mixed occupancy between Cu and Zn in the z ¼ 1/4 and z ¼ 3/4 cationic layers results in a disordered kesterite configuration (DKS, SG I 4 2 m, Z ¼ 2, Fig.…”