The role of interparticle heterogeneities in the selenization pathway of Cu–Zn–Sn–S nanoparticle thin films: a real-time study

Abstract

a Real-time energy dispersive x-ray diffraction (EDXRD) analysis has been utilized to observe the selenization of Cu-Zn-Sn-S nanoparticle films coated from three nanoparticle populations: Cu-and Sn-rich particles roughly 5 nm in size, Zn-rich nanoparticles ranging from 10 to 20 nm in diameter, and a mixture of both types of nanoparticles (roughly 1:1 by mass), which corresponds to a synthesis recipe yielding CZTSSe solar cells with reported total-area efficiencies as high as 7.9%. The EDXRD studies presented herein show that the formation of copper selenide intermediates during the selenization of mixedparticle films can be primarily attributed to the small, Cu-and Sn-rich particles. Moreover, the formation of these copper selenide phases represents the first stage of the CZTSSe grain growth mechanism. The large, Zn-rich particles subsequently contribute their composition to form micrometer-sized CZTSSe grains. These findings enable further development of a previously proposed selenization pathway to account for the roles of interparticle heterogeneities, which in turn provides a valuable guide for future optimization of processes to synthesize high quality CZTSSe absorber layers.

Enabling fine-grain free 2-micron thick CISe/CIGSe film fabrication via a non-hydrazine based solution processing route

“…Reports in the literature have shown that the process of sulfide to selenide conversion in the case of CZTS film, or even pure metal to metal selenide in the case of CIGS film proceeds through the formation of Cu-Se rich liquid phase which starts nucleating copper selenide material. [32][33][34][35] The remaining cations then start diffusing towards these nuclei making desired ternary or quaternary selenide materials in the form of grains on the surface of the film that continues to grow towards the bottom (Figure 7a). In this process, especially when the film exceeds a certain thickness, the rate of mass transfer and the reaction rates between copper and indium chalcogenides could affect the elemental distributions and hence the grain growth in the film.…”

Chemistry and Dynamics of Ge in Kesterite: Toward Band-Gap-Graded Absorbers

“…As previously observed for the selenization of Cu−Zn−Sn−S nanoparticle precursors, the formation of Cu−Se phases precedes the formation of CZT(Ge)Se. 30,42 The formation of CZTSe, with barely any incorporation of Ge in the lattice; GeSe; and a small amount of SnSe 2 occurs at temperatures around 380°C ( Figure 5a …”

Growth and Photovoltaic Device Application of Cu2BaGe1–xSnxSe4 Films Prepared by Selenization of Sequentially Deposited Precursors

“…Such migration of Cu binary phases to the film surfaces has been observed for other Cu-containing chalcogenide films such as CBTS 18 and CZTS. 23,24 Copper binary phases also appear in the XRD data for films of Cu−Ba (Sn and Ge left out of stack) that have been similarly processed at 350 °C (Figure S10). Analogous treatment of a pure Ba film leads to primarily the BaSe 3 phase (Figure S10).…”