Evolution of Cu<sub>2</sub>ZnSnS<sub>4</sub> during Non-Equilibrium Annealing with Quasi-in Situ Monitoring of Sulfur Partial Pressure

Ren, Yi; Ross, Nils; Larsen, Jes K.; Rudisch, Katharina; Scragg, Jonathan J.; Platzer‐Björkman, Charlotte

doi:10.1021/acs.chemmater.7b00671

Cited by 42 publications

(49 citation statements)

References 45 publications

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“…Analysis of the X‐ray diffraction (XRD) spectra, see Figure a, showed that the films reacted with S and formed preferentially SnS 2 at lower temperatures and Sn 2 S 3 at higher temperatures. This observation is consistent with previous findings related to the behavior of Sn and S content in the present anneal setup . It follows from the fact that the partial pressure of S ( P s ) in the initial phase of the anneal increases rapidly initially as the elemental S evaporates and then decays during the rest of the anneal time as the system (graphite box) is not fully tight (see, e.g., a previous study).…”

Section: Resultssupporting

confidence: 93%

“…For the devices with Mo back contacts in this study, long anneal times (at 580 °C) typically result in deteriorated devices due to loss of S and Sn according to literature . In this study, however, it was repeatedly found that long anneal times resulted in not only working devices, but also better devices compared with those processed with shorter anneal times.…”

Section: Resultssupporting

confidence: 49%

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Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu₂ZnSnS₄ Thin‐Film Solar Cells

Englund

Kubart

Keller

et al. 2019

Physica Status Solidi (a)

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Antimony-doped tin oxide (Sn 2 O 3 :Sb, ATO) is investigated as a transparent back contact for Cu 2 ZnSnS 4 (CZTS) thin-film solar cells. The stability of the ATO under different anneal conditions and the effect from ATO on CZTS absorber growth are studied. It is found that ATO directly exposed to sulfurizing anneal atmosphere reacts with S, but when covered by CZTS, it does not deteriorate when annealed at T < 550 C. The electrical properties of ATO are even found to improve when CZTS is annealed at T ¼ 534 C. At T ¼ 580 C, it is found that ATO reacts with S and degrades. Analysis shows repeatedly that ATO affects the absorber growth as large amounts of SnÀS secondary compounds are found on the absorber surfaces. Time-resolved anneal series show that these compounds form early during anneal and evaporate with time to leave pinholes behind. Device performance can be improved by addition of Na prior to annealing. The best CZTS device on ATO back contact herein has an efficiency of 2.6%. As compared with a reference on a Mo back contact, a similar opencircuit voltage and short-circuit current density are achieved, but a lower fill factor is measured.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 49%

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu₂ZnSnS₄ Thin‐Film Solar Cells

Englund

Kubart

Keller

et al. 2019

Physica Status Solidi (a)

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“…33−36 The poor capability of the annealing reactors to maintain high S and Se partial pressure with time due to leakage or vapor absorption in the reactor walls has also been associated with Sn loss. 37 The evaporation of SnSe 2 occurs incongruently as represented by eqs 1 and 2. 38 Under high Se partial pressure, SnSe 2 would be stabilized as eq 1 would proceed toward the lefthand side.…”

Section: Methodsmentioning

confidence: 99%

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

et al. 2017

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The selenization of metallic Cu−Zn−Sn−Ge precursors is a promising route for the fabrication of low-cost and efficient kesterite thin-film solar cells. Nowadays, efficiencies of kesterite solar cells are still below 13%. For Cu(In,Ga)Se 2 solar cells, the formation of compositional gradients along the depth of the absorber layer has been demonstrated to be a key requirement for producing thin-film solar cells with conversion efficiencies above the 22% level. No clear understanding has been reached so far about how to produce these gradients in an efficient manner for kesterite compounds, but among the possible candidates, Ge arises as one of the most promising ones. In the present work, we evaluate the potential of incorporating Ge in Cu 2 ZnSnSe 4 to produce compositional gradients in kesterites. Synchrotron-based in situ energydispersive X-ray diffraction and X-ray fluorescence have been used to study the selenization of Cu−Zn−Sn−Ge metallic precursors. We propose a reaction mechanism for the incorporation of Ge atoms into the kesterite lattice after the formation of Cu 2 ZnSnSe 4 . Electron microscopy reveals that the annealing process leads to Cu 2 Zn(Sn,Ge)Se 4 absorber layers with an increase of Ge content toward the back contact with independence of the original location of Ge in the precursor layer. The effect of the Ge gradient on the optoelectronic properties of the absorber layer has been evaluated with room-temperature cathodoluminescence. The implications of the results for the development of kesterite solar cells are discussed, with the aim of encouraging new synthesis routes for compositionally graded absorbers.

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“…3 It has been shown that both etching with (NH 4 ) 2 S solution and using thermal evaporation during the annealing process are effective approaches for removing SnS on CZTS surface. 8 Regarding the CZTS rear, SnS could form due to the initial CZTS composition 23 as well as the back contact decomposition. 24 Therefore, to control the SnS formation on the CZTS rear, efforts to develop suitable CZTS composition and to passivate the back contact are required.…”

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Investigation of the SnS/Cu₂ZnSnS₄ Interfaces in Kesterite Thin-Film Solar Cells

et al. 2017

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Kesterite Cu 2 ZnSnS 4 (CZTS), having only earthabundant elements, is a promising solar cell material. Nevertheless, the impact of the SnS secondary phase, which often forms alongside CZTS synthesis at high annealing temperature, on CZTS solar cells is poorly studied. We confirm, by means of X-ray diffraction, Raman scattering, and energy dispersive X-ray spectroscopy mapping, that this phase tends to segregate at both the surface and the back side of annealed CZTS films with Cu-poor and Zn-rich composition. Using electron beam-induced current measurements, it is further demonstrated that the formation of SnS on the CZTS surface is harmful for solar cells, whereas the SnS phase can be beneficial for solar cells when it segregates on the CZTS rear. This positive contribution of SnS could stem from a passivation effect at the CZTS/SnS rear interface. This work opens new possibilities for an alternative interface development for kesterite-based photovoltaic technology.

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Evolution of Cu₂ZnSnS₄ during Non-Equilibrium Annealing with Quasi-in Situ Monitoring of Sulfur Partial Pressure

Cited by 42 publications

References 45 publications

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu₂ZnSnS₄ Thin‐Film Solar Cells

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu₂ZnSnS₄ Thin‐Film Solar Cells

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

Investigation of the SnS/Cu₂ZnSnS₄ Interfaces in Kesterite Thin-Film Solar Cells

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Evolution of Cu2ZnSnS4 during Non-Equilibrium Annealing with Quasi-in Situ Monitoring of Sulfur Partial Pressure

Cited by 42 publications

References 45 publications

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu2ZnSnS4 Thin‐Film Solar Cells

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu2ZnSnS4 Thin‐Film Solar Cells

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

Investigation of the SnS/Cu2ZnSnS4 Interfaces in Kesterite Thin-Film Solar Cells

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Evolution of Cu₂ZnSnS₄ during Non-Equilibrium Annealing with Quasi-in Situ Monitoring of Sulfur Partial Pressure

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu₂ZnSnS₄ Thin‐Film Solar Cells

Antimony‐Doped Tin Oxide as Transparent Back Contact in Cu₂ZnSnS₄ Thin‐Film Solar Cells

Investigation of the SnS/Cu₂ZnSnS₄ Interfaces in Kesterite Thin-Film Solar Cells