Sulfurization of Co-Evaporated Cu(In,Ga)Se<sub>2</sub> as a Postdeposition Treatment

Larsen, Jes K.; Keller, Jan; Lundberg, Olle; Jarmar, Tobias; Riekehr, Lars; Scragg, Jonathan J.; Platzer‐Björkman, Charlotte

doi:10.1109/jphotov.2018.2793759

Cited by 23 publications

(43 citation statements)

References 25 publications

(35 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Following a short air exposure (≈2 min), the samples were subjected to annealing in elemental S atmosphere for either 10 min (for material characterization) or 20 min (for subsequent solar cell preparation) in a customized vacuum furnace at 530 °C and an Ar pressure of 70 mbar. Further details about the sulfurization system can be found in a previous study . For solar cell testing, only six samples with different CGI values (0.57–0.94) were further processed by adding 50 nm of CdS (CBD) and a sputtered i‐ZnO(70 nm)/ZnO:Al(210 nm) bilayer.…”

Section: Methodsmentioning

confidence: 99%

“…Further details about the sulfurization system can be found in a previous study. [14] For solar cell testing, only six samples with different CGI values (0.57-0.94) were further processed by adding 50 nm of CdS (CBD) and a sputtered i-ZnO(70 nm)/ZnO:Al(210 nm) bilayer. Each of the six samples was finally sectioned into 25 solar cells with an area of A ¼ 0.05 cm 2 by mechanical scribing.…”

Section: Solar Cell Processing and Post-sulfurizationmentioning

confidence: 99%

“…[8,[11][12][13] Previous experiments have shown that this sulfur treatment results in the formation of a ternary CuInS 2 surface layer, independent of the initial presence of Ga at the surface. [14] In addition, S was found to diffuse along the grain boundaries toward the back contact. [11,15,16] As CuInS 2 , in contrast to CuInSe 2 , shows very little tolerance to copper off-stoichiometry, [17] an increased Cu content was measured in the CuInS 2 top layer.…”

Section: Introductionmentioning

confidence: 99%

“…This high bandgap interlayer may act as an electron transport barrier and is proposed to be responsible for significant fill factor (FF) losses observed for corresponding solar cells. [14] Preliminary, unpublished experiments indicate that already very little Ga concentrations at the surface (<1 at.%) are detrimental if a post-sulfurization treatment is intended. This may also explain the impressive improvement by sulfurization in the aforementioned study, where CIGS absorbers with no Ga at the surface were processed.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se₂ Films and Corresponding Solar Cell Performance

Keller

Bilousov

Wallin

et al. 2019

Physica Status Solidi (a)

Self Cite

View full text Add to dashboard Cite

Herein, the effect of the initial copper content of co‐evaporated Cu(In1−x,Gax)Se2 (CIGS) absorber films on the impact of a post‐annealing step in elemental sulfur atmosphere is studied. The Cu concentration is varied over a wide range ([Cu]/[III] = CGI = 0.57–1.23), allowing to identify composition‐dependent trends in phase formation, chemical rearrangements, and solar cell performance after sulfurization. For all samples, a ternary CuInS2 layer forms at the surface. In addition, sulfur 1) is incorporated in randomly distributed CuIn(S,Se)2 mixed crystals underneath CuInS2; 2) diffuses into multidimensional defects (e.g., dislocations and grain boundaries); and 3) is bound in Na–In–S surface plates. It is found that Cu‐poor absorber composition (CGI ≤ 0.82) favors CuInS2 growth as compared with close‐stoichiometric CIGS films, driven by a faster diffusion of Cu toward the surface. For Cu‐rich absorbers (CGI > 1), Se—S exchange is significantly accelerated, presumably by the presence of Cu2−xSe phases reacting to Cu2−xS and eventually catalyzing CuInS2 formation. Finally, open‐circuit voltage (VOC), fill factor (FF), and efficiency (η) of corresponding solar cells increase after sulfurization with increasing CGI until stoichiometry is reached. The result is explained by a mitigated Cu depletion of the absorber bulk after sulfurization for close‐stoichiometric CIGS.

show abstract

Section: Methodsmentioning

confidence: 99%

Section: Solar Cell Processing and Post-sulfurizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se₂ Films and Corresponding Solar Cell Performance

Keller

Bilousov

Wallin

et al. 2019

Physica Status Solidi (a)

Self Cite

View full text Add to dashboard Cite

show abstract

“…[7][8][9][10] The large potential of this cell combination was recently highlighted by a new record efficiency of 24.2% for a 2-terminal device. [11] To combine the greater flexibility in tailoring the absorber composition (Ga/In profile) with the surface modifications by the S-treatment, a post-annealing of co-evaporated CIGS in either H 2 S [3,[12][13][14] or elemental sulfur [15][16][17][18][19] was frequently studied. In the present contribution, the latter approach is followed, mainly to avoid usage of toxic H 2 S gas.…”

Section: Introductionmentioning

confidence: 99%

Heavy Alkali Treatment of Post‐Sulfurized Cu(In,Ga)Se₂ Layers: Effect on Absorber Properties and Solar Cell Performance

et al. 2020

Self Cite

View full text Add to dashboard Cite

This contribution evaluates a sequential post‐deposition treatment of Cu(In,Ga)Se2 (CIGS) films, consisting of 1) a post‐sulfurization in elemental S‐atmosphere and 2) a subsequent treatment by heavy alkali fluorides (Alk‐PDT). First, the effect of the sulfurization step on the corresponding solar cell performance is investigated and optimum process parameters, leading to an efficiency improvement, are identified. Losses in carrier collection observed after S‐incorporation are attributed to an increased grain boundary (GB) recombination. It is found that the corresponding reduction in short‐circuit current density can be mitigated by a RbF‐ or KF‐PDT, supposedly by depleting GBs in Cu. However, in strong contrast to non‐sulfurized CIGS, the Alk‐PDT results in a lower open‐circuit voltage and distortions in the current–voltage (I–V) characteristics for sulfurized absorbers. Possible explanations are the absence of a wide‐gap surface phase and/or air exposure between the post‐treatment steps. It is further proposed that a back contact barrier may be responsible for the distortions in I–V.

show abstract

Experimental and Theoretical Study of Stable and Metastable Phases in Sputtered CuInS₂

et al. 2022

Self Cite

View full text Add to dashboard Cite

The chalcopyrite Cu(In,Ga)S2 has gained renewed interest in recent years due to the potential application in tandem solar cells. In this contribution, a combined theoretical and experimental approach is applied to investigate stable and metastable phases forming in CuInS2 (CIS) thin films. Ab initio calculations are performed to obtain formation energies, Xray diffraction patterns, and Raman spectra of CIS polytypes and related compounds. Multiple CIS structures with zinc-blende and wurtzite-derived lattices are identified and their XRD/Raman patterns are shown to contain overlapping features, which could lead to misidentification. Thin films with compositions from Cu-rich to Cu-poor are synthesized with a two-step approach based on sputtering from binary targets followed by high-temperature sulfurization. It is discovered that several CIS polymorphs are formed when growing the material with this approach. In the Cu-poor material, wurtzite CIS is observed for the first time in sputtered thin films along with chalcopyrite CIS and CuAu-ordered CIS. Once the wurtzite CIS phase has formed, it is difficult to convert into the stable chalcopyrite polymorph. CuIn5S8 and NaInS2 accommodating In-excess are found alongside the CIS polymorphs. It is argued that the metastable polymorphs are stabilized by off-stoichiometry of the precursors, hence tight composition control is required.

show abstract

Sulfurization of Co-Evaporated Cu(In,Ga)Se₂ as a Postdeposition Treatment

Cited by 23 publications

References 25 publications

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se₂ Films and Corresponding Solar Cell Performance

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se₂ Films and Corresponding Solar Cell Performance

Heavy Alkali Treatment of Post‐Sulfurized Cu(In,Ga)Se₂ Layers: Effect on Absorber Properties and Solar Cell Performance

Experimental and Theoretical Study of Stable and Metastable Phases in Sputtered CuInS₂

Contact Info

Product

Resources

About

Sulfurization of Co-Evaporated Cu(In,Ga)Se2 as a Postdeposition Treatment

Cited by 23 publications

References 25 publications

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se2 Films and Corresponding Solar Cell Performance

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se2 Films and Corresponding Solar Cell Performance

Heavy Alkali Treatment of Post‐Sulfurized Cu(In,Ga)Se2 Layers: Effect on Absorber Properties and Solar Cell Performance

Experimental and Theoretical Study of Stable and Metastable Phases in Sputtered CuInS2

Contact Info

Product

Resources

About

Sulfurization of Co-Evaporated Cu(In,Ga)Se₂ as a Postdeposition Treatment

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se₂ Films and Corresponding Solar Cell Performance

Effect of Cu Content on Post‐Sulfurization of Cu(In,Ga)Se₂ Films and Corresponding Solar Cell Performance

Heavy Alkali Treatment of Post‐Sulfurized Cu(In,Ga)Se₂ Layers: Effect on Absorber Properties and Solar Cell Performance

Experimental and Theoretical Study of Stable and Metastable Phases in Sputtered CuInS₂