The Optical Diode Ideality Factor Enables Fast Screening of Semiconductors for Solar Cells

Babbe, Finn; Choubrac, Léo; Siebentritt, Susanne

doi:10.1002/solr.201800248

Cited by 34 publications

(42 citation statements)

References 59 publications

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“…In an aqueous solution, AS ((NH 4 ) 2 S) dissociates into NH 4 + and S 2− and NaS (Na 2 S) dissociates into Na + and S 2− ions. [ 57,58 ] We assume that the S 2− ion diffuses to the surface of the absorber and reacts to fill any anion vacancies. However, the exact sulfur species present in solution depends on the pH, with the more basic NaS‐PDT having a higher proportion of S 2− ions to HS − ions as compared with the AS‐PDT.…”

Section: Discussion: Impact Of S‐salt In S‐pdtmentioning

confidence: 99%

Passivating Surface Defects and Reducing Interface Recombination in CuInS₂ Solar Cells by a Facile Solution Treatment

et al. 2021

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Interface recombination at the absorber surface impedes the efficiency of a solar cell with an otherwise excellent absorber. The internal voltage or quasi‐Fermi‐level splitting (qFLs) measures the quality of the absorber. Interface recombination reduces the open‐circuit voltage (VOC) with respect to the qFLs. A facile solution‐based sulfur postdeposition treatment (S‐PDT) is explored to passivate the interface of CuInS2 grown under Cu‐rich conditions, which show excellent qFLs values, but much lower VOCs. The absorbers are treated in S‐containing solutions at 80 °C. Absolute calibrated photoluminescence and current–voltage measurements demonstrate a reduction of the deficit between qFLs and VOC by almost one‐third compared with the untreated device. Temperature dependence of the open‐circuit voltage shows increased activation energy for the dominant recombination path, indicating less interface recombination. In addition, capacitance transients reveal the presence of slow metastable defects in the untreated solar cell. The slow response is considerably reduced by the S‐PDT, suggesting passivation of these slow metastable defects. The results demonstrate the effectiveness of solution‐based S‐treatment in passivating defects, presenting a promising strategy to explore and reduce defect states near the interface of chalcogenide semiconductors.

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Section: Discussion: Impact Of S‐salt In S‐pdtmentioning

confidence: 99%

Passivating Surface Defects and Reducing Interface Recombination in CuInS₂ Solar Cells by a Facile Solution Treatment

et al. 2021

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“…The same study demonstrated a considerably larger difference between qFLs and V OC in Cu-rich solar cells, indicating that interface recombination poses an additional loss mechanism in Cu-rich Cu(In, Ga)Se 2 . This was confirmed by the investigation of the diode factor in Cu-rich and Cu-poor absorbers and solar cells [24]. In summary: Cu-rich Cu(In, Ga)Se 2 solar cells suffer from interface recombination, but it is not clear why the buffer-absorber interface is different from the one with Cu-poor absorbers.…”

Section: Introductionmentioning

confidence: 94%

Challenge in Cu-rich CuInSe2 thin film solar cells: Defect caused by etching

Elanzeery

Melchiorre

Sood

et al. 2019

Phys. Rev. Materials

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Thin-film solar cells consist of several layers. The interfaces between these layers can provide critical recombination paths and consequently play a vital role in the efficiency of the solar cell. One of the main challenges for polycrystalline semiconductor absorber materials is the absorber-buffer interface. The Cu(In, Ga)Se 2 system is particularly interesting in this context, since Cu-rich absorbers are dominated by recombination at the interface, while Cu-poor ones are not. This paper unveils the root cause of the challenge in the interface of Cu-rich solar cells in terms of a Se-related defect with an activation energy of 200 ± 20 meV. This defect causes interface recombination and is responsible for the deficiency of open-circuit voltage in Cu-rich cells. Moreover, this paper demonstrates that the origin of this defect is due to the etching step necessary to remove secondary phases. Postdeposition surface treatments or modified buffer layers are shown to passivate this defect, to reduce interface recombination, and to increase the efficiency.

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“…But quasi‐Fermi level splitting will increase within a diffusion length toward the bulk. Because the higher quasi‐Fermi level splitting leads also to higher luminescence intensity the photoluminescence measurement will detect the higher quasi‐Fermi level splitting in the bulk, whereas V OC is limited by the smaller quasi‐Fermi level splitting at the surface . However, this difference is minimized in absorbers with good transport properties, i.e., long diffusion length, typical for these high efficiency absorbers.…”

Section: Effects Of Post‐deposition Treatment With Heavy Alkalismentioning

confidence: 99%

“…Because the higher quasi-Fermi level splitting leads also to higher luminescence intensity [57] the photoluminescence measurement will detect the higher quasi-Fermi level splitting in the bulk, whereas V OC is limited by the smaller quasi-Fermi level splitting at the surface. [58] However, this difference is minimized in absorbers with good transport properties, i.e., long diffusion length, typical for these high efficiency absorbers. The fact that quasi-Fermi level splitting and open-circuit voltage increase by the same amount upon treatment could hint that the reduction of nonradiative recombination occurs mostly in the bulk of the absorber, not at the surface.…”

Section: Bulk Effectsmentioning

confidence: 99%

Heavy Alkali Treatment of Cu(In,Ga)Se₂Solar Cells: Surface versus Bulk Effects

Siebentritt

Avancini

Bär

et al. 2020

Advanced Energy Materials

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Chalcopyrite solar cells achieve efficiencies above 23%. The latest improvements are due to post‐deposition treatments (PDT) with heavy alkalis. This study provides a comprehensive description of the effect of PDT on the chemical and electronic structure of surface and bulk of Cu(In,Ga)Se2. Chemical changes at the surface appear similar, independent of absorber or alkali. However, the effect on the surface electronic structure differs with absorber or type of treatment, although the improvement of the solar cell efficiency is the same. Thus, changes at the surface cannot be the only effect of the PDT treatment. The main effect of PDT with heavy alkalis concerns bulk recombination. The reduction in bulk recombination goes along with a reduced density of electronic tail states. Improvements in open‐circuit voltage appear together with reduced band bending at grain boundaries. Heavy alkalis accumulate at grain boundaries and are not detected in the grains. This behavior is understood by the energetics of the formation of single‐phase Cu‐alkali compounds. Thus, the efficiency improvement with heavy alkali PDT can be attributed to reduced band bending at grain boundaries, which reduces tail states and nonradiative recombination and is caused by accumulation of heavy alkalis at grain boundaries.

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The Optical Diode Ideality Factor Enables Fast Screening of Semiconductors for Solar Cells

Cited by 34 publications

References 59 publications

Passivating Surface Defects and Reducing Interface Recombination in CuInS₂ Solar Cells by a Facile Solution Treatment

Passivating Surface Defects and Reducing Interface Recombination in CuInS₂ Solar Cells by a Facile Solution Treatment

Challenge in Cu-rich CuInSe2 thin film solar cells: Defect caused by etching

Heavy Alkali Treatment of Cu(In,Ga)Se₂Solar Cells: Surface versus Bulk Effects

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The Optical Diode Ideality Factor Enables Fast Screening of Semiconductors for Solar Cells

Cited by 34 publications

References 59 publications

Passivating Surface Defects and Reducing Interface Recombination in CuInS2 Solar Cells by a Facile Solution Treatment

Passivating Surface Defects and Reducing Interface Recombination in CuInS2 Solar Cells by a Facile Solution Treatment

Challenge in Cu-rich CuInSe2 thin film solar cells: Defect caused by etching

Heavy Alkali Treatment of Cu(In,Ga)Se2Solar Cells: Surface versus Bulk Effects

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Passivating Surface Defects and Reducing Interface Recombination in CuInS₂ Solar Cells by a Facile Solution Treatment

Passivating Surface Defects and Reducing Interface Recombination in CuInS₂ Solar Cells by a Facile Solution Treatment

Heavy Alkali Treatment of Cu(In,Ga)Se₂Solar Cells: Surface versus Bulk Effects