Effect of the KF post-deposition treatment on grain boundary properties in Cu(In, Ga)Se2 thin films

Nicoara, Nicoleta; Lepetit, Thomas; Arzel, Ludovic; Harel, Sylvie; Barreau, Nicolas; Sadewasser, Sascha

doi:10.1038/srep41361

Cited by 85 publications

(81 citation statements)

References 43 publications

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“…The corresponding solar cells also show the highest open‐circuit voltage. In fact, for KF‐treated Cu(In,Ga)Se 2 , a reduced variation of band bending at grain boundaries was previously also observed, and it was shown by numerical simulations that smaller downward band bending at grain boundaries leads to higher open‐circuit voltage . This observation indicates that successful alkali PDTs which lead to an improved open‐circuit voltage also reduce the band bending (or at least its variation) at grain boundaries .…”

Section: Effects Of Post‐deposition Treatment With Heavy Alkalismentioning

confidence: 57%

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

Siebentritt

Avancini

Bär

et al. 2020

Advanced Energy Materials

126

195

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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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Section: Effects Of Post‐deposition Treatment With Heavy Alkalismentioning

confidence: 57%

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

Siebentritt

Avancini

Bär

et al. 2020

Advanced Energy Materials

126

195

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“…[ 64 ] From KPFM measurement, we obtained CPD values between a metallic AFM tip and a sample and is denoted as V CPD , which can be defined in Equation (1) and identified as the work function difference between the tip and the sample, where Φ is the work function. [ 65,66 ]

V_{CPD} = ({normalΦ}_{tip} - {normalΦ}_{sample}) / - e

…”

Section: Resultsmentioning

confidence: 99%

Efficient Perovskite Solar Cells by Reducing Interface‐Mediated Recombination: a Bulky Amine Approach

Liang

Luo

et al. 2020

Advanced Energy Materials

230

199

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meantime, the ease of the solution process at low temperature renders this technology up-and-coming for large-scale low-cost manufacture. However, these solution-processed perovskite films are usually polycrystalline, which readily form defects at the grain boundaries and on the surface of the films. [1][2][3][4][5][6] Such defects are the center of non-radiative recombination of photo-generated electrons and holes, which causes shorter carrier lifetime and lower open-circuit voltage (V OC ). Hence, in real devices, higher recombination rate occurs close to the interface of the sequentially deposited layers. For typical n-i-p perovskite solar cells (PSCs), the perovskite/hole transport layer (HTL) interface holds the high defect density, such as cation/anion vacancy and dangling bonds, etc., [7,8] resulting in defect-assisted recombination. Additionally, the energy level mis-alignment near the interface due to quasi-fermi level pinning will increase recombination velocity [9] and the recombination loss occurs inevitably across interfaces between holes in HTL and minority carriers (electron) in the perovskite, or HTL themselves. [10,11] These existing recombination loss channels at the surface/ interface of the perovskite will severely limit the V OC and overall efficiency of PSCs.Many studies have demonstrated that passivation is an efficient method to lessen the non-radiative recombination loss at the surface/interface of the perovskite in n-i-p PSCs. For example, excess PbI 2 [4,[12][13][14] was believed to passivate the grain boundaries and interface of electron transport layer with perovskite; conjugated polymers [15] and insulating poly(methyl methacrylate) [16,17] were also used to passivate the interface of perovskite/HTL. Recently, various ammonium halide compounds, [8,18,19] especially bulky organic ammonium halide salts were adopted to passivate the surface of perovskite, such as 1,8-octanediammonium iodide, [3] adamantylammonium hydroiodide, [7] (fluorine-)phenylethylammonium iodide (F-)PEAI, [20][21][22][23] n-hexyl trimethyl ammonium bromide, [24] etc. They could interact with the undercoordinated ions or form low-dimensional perovskite phases to passivate the surface/ interface of bulk perovskite. The stability of devices was also usually improved due to the suppression of ionic migration by the packed organic moiety or the formation of hydrophobic low-dimensional perovskites. [7,23,25] A very recent work by Jiang et al. found exceptionally that the insulating PEAI salt, rather than the 2D layered PEA 2 PbI 4 perovskite, served as a moreThe presence of non-radiative recombination at the perovskite surface/ interface limits the overall efficiency of perovskite solar cells (PSCs). Surface passivation has been demonstrated as an efficient strategy to suppress such recombination in Si cells. Here, 1-naphthylmethylamine iodide (NMAI) is judiciously selected to passivate the surface of the perovskite film. In contrast to the popular phenylethylammonium iodide, NMAI post-treatment primarily leaves NMAI sal...

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“…It is suggested that this surface modification reduces the interface recombination and improves the initial CdS buffer layer growth and the in‐diffusion of Cd and/or S . Even a beneficial effect on the surface‐near grain boundary properties was discussed . Overall, a potential improvement of all solar cell parameters is observed by a KF‐PDT.…”

Section: Introductionmentioning

confidence: 99%

Effect of KF absorber treatment on the functionality of different transparent conductive oxide layers in CIGSe solar cells

Keller

Chalvet

Joel

et al. 2017

Progress in Photovoltaics

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Effect of the KF post-deposition treatment on grain boundary properties in Cu(In, Ga)Se2 thin films

Cited by 85 publications

References 43 publications

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

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

Efficient Perovskite Solar Cells by Reducing Interface‐Mediated Recombination: a Bulky Amine Approach

Effect of KF absorber treatment on the functionality of different transparent conductive oxide layers in CIGSe solar cells

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Effect of the KF post-deposition treatment on grain boundary properties in Cu(In, Ga)Se2 thin films

Cited by 85 publications

References 43 publications

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

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

Efficient Perovskite Solar Cells by Reducing Interface‐Mediated Recombination: a Bulky Amine Approach

Effect of KF absorber treatment on the functionality of different transparent conductive oxide layers in CIGSe solar cells

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

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