In situXRD investigation of Cu₂ZnSnSe₄thin film growth by thermal co-evaporation

Abstract

The deposition of a Cu2ZnSnSe4 (CZTSe) thin film with a multi‐stage co‐evaporation process is investigated with time‐resolved in situ X‐ray diffraction (in situ XRD). For the experiment a novel setup intended for in situ analysis of thin film deposition processes was used. The in situ data confirm the former observation that CZTSe growth is delayed with deposition of only Cu2−xSe and ZnSe in the initial process stage and provide new insight into the evolution of the appearing phases. In Zn‐rich deposition conditions, ZnSe deposited at the beginning may not be consumed by the growing CZTSe but remain as an unreacted layer at the interface to the Mo back contact. Cu2−xSe growth starts with the formation of a Cu rich phase, which is reduced to a Cu poor phase in the process. Furthermore, our results show that in situ XRD at elevated temperatures is able to distinguish between ZnSe and CZTSe and that it can be used for the detection of ZnSe as secondary phase.

Different Bandgaps in Cu$_2$ ZnSnSe$_4$: A High Temperature Coevaporation Study

“…Solar cells made from the break-off experiment did not give working devices. The results are in according with earlier results [15], [16]. The pyrometer signal shown in Fig.…”

“…It is clearly visible that the Zn/Sn is close to unity in the majority of the backsurface, except in the regions where the Zn rich patches are present. Based on the preceding analysis and other literature reports [15], [16], [18], we conclude that there is a large amount of ZnSe still present at the Mo/CZTSe interface despite the somewhat lower onset temperature during growth and the high Sn and Se overpressures during growth. Since Sn is not incorporated in the beginning of the growth process, ZnSe and Cu x Se are formed.…”

“…The two-stage process is necessary, since the reaction of all constituents is slow. It has been shown by Kaune et al [16] that after the first stage, there is a substantial amount of Cu x Se present in the CZTSe absorbers. Only during the second stage, where no Cu is supplied, the system has enough time to fully react and the Cu x Se are consumed, which is prerequisite for working devices.…”

Fabrication of 5.2% efficient Cu2ZnSn(S,Se)4 solar cells using DC‐sputtered metal precursors followed by sulfo‐selenization

“…The non-metal Se powder can be easily diffused in the precursor at or above 500 °C. Moreover, the diffused Se atoms form large CZTSSe grains which can reduce the grain boundaries [3,12]. The high number of grain boundaries is the main cause in drop of current density in TFSCs while the large sized grains decrease the band gap energy [3].…”

In-situ XRD study of alloyed Cu2ZnSnSe4–CuInSe2 thin films for solar cells

“…Soda-lime glass covered with industrially sputtered Mo from the Manz AG was used as substrate. The initial substrate temperature was T Sub = 450 • C. After depositing a 150 nm thick layer, the substrate was heated to T Sub = 500 • C. Elemental Cu, Zn, Sn, In and Se were evaporated from Radak II furnaces and Createc effusion cells in a two-stage deposition process with a Cu-rich first and a Cu-free second stage [5,6,7]. Infrared and red LLS was used to determine the end of the first and second process stage and the transition from Cu-rich to Cu-poor stoichiometry.…”