Impact of Water Ingress on Molybdenum Thin Films and Its Effect on Cu(In,Ga)Se<sub>2</sub> Solar Cells

Karki, Shankar; Marsillac, Sylvain; Deitz, Julia I.; Rajan, Grace; Soltanmohammad, Sina; Poudel, Deewakar; Belfore, Benjamin; Bhandari, G.N.; Grassman, Tyler J.; Rockett, Angus

doi:10.1109/jphotov.2019.2959947

Cited by 21 publications

(8 citation statements)

References 28 publications

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“…The depth profiles for the positive ions of the main elements are shown in Figure 3. In the reference samples, the constant ion profiles for CIGS main elements (Cu, In and Se) and the presence of alkali are consistent with CIGS films deposited by a three-stage process [13]. No change was observed for the Cu, In or Se profiles before and after annealing.…”

Section: Second Stage Temperature Dependencesupporting

confidence: 68%

In Situ Recrystallization of Co-Evaporated Cu(In,Ga)Se2 Thin Films by Copper Chloride Vapor Treatment towards Solar Cell Applications

et al. 2021

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Cu(In,Ga)Se2 (or CIGS) thin films and devices were fabricated using a modified three-stage process. Using high deposition rates and a low temperature during the process, a copper chloride vapor treatment was introduced in between the second and third stages to enhance the films properties. X-ray diffraction and scanning electron microscopy demonstrate that drastic changes occur after this recrystallization process, yielding films with much larger grains. Secondary ion mass spectrometry shows that the depth profile of many elements is not modified (such as Cu, In and Se) while others change dramatically (such as Ga and Na). Because of the competing effects of these changes, not all parameters of the solar cells are enhanced, yielding an increase of 15% in the device efficiency at the most.

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Section: Second Stage Temperature Dependencesupporting

confidence: 68%

In Situ Recrystallization of Co-Evaporated Cu(In,Ga)Se2 Thin Films by Copper Chloride Vapor Treatment towards Solar Cell Applications

et al. 2021

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“…There is a small decrease in

J_{SC}

due to reduced collection in the long‐wavelength region for the samples that are air annealed after CIGSe with and without Na (AA‐CIGSe‐wNa and AA‐CIGSe‐w/oNa). Taking into account that an increased charge carrier density observed for these devices (see Table 2) will cause a reduced width of the space charge region, a smaller effective collection length is suggested to be the reason for this observation 60,61 …”

Section: Discussion—degradation Mechanisms In Cigse Solar Cells Under Thermal Stressmentioning

confidence: 98%

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se₂ thin‐film solar cells after exposure to thermal stress: Understanding the role of Na

Yetkin

Kodalle

Bertram

et al. 2021

Progress in Photovoltaics

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Due to their tunable bandgap energy, Cu(In,Ga)Se2 (CIGSe) thin‐film solar cells are an attractive option for use as bottom devices in tandem configurations. In monolithic tandem devices, the thermal stability of the bottom device is paramount for reliable application. Ideally, it will permit the processing of a top device at the required optimum process temperature. Here, we investigate the degradation behavior of chemical bath deposited (CBD) CdS‐buffered CIGSe thin‐film solar cells with and without Na incorporation under thermal stress in ambient air and vacuum with the aim to gain a more detailed understanding of their degradation mechanisms. For the devices studied, we observe severe degradation after annealing at 300°C independent of the atmosphere. The electrical and compositional properties of the samples before and after a defined application of thermal stress are studied. In good agreement with literature reports, we find pronounced Cd diffusion into the CIGS absorber layer. In addition, for Na‐containing samples, the observed degradation can be mainly explained by the formation of Na‐induced acceptor states in the TCO front contact and a back contact barrier formation due to the out‐diffusion of Na. Supported by numerical device simulation using SCAPS‐1D, various possible degradation models are discussed and correlated with our findings.

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“…9,15 Additionally, Na-and Se-containing products were observed on the surface of degraded molybdenum layer after DH tests. 15,17,18 The CIGS absorber is not considered to be the most sensitive cell component to humidity in accelerated weathering tests. This layer contains some alkali elements (Na, K) at grain boundaries, which improve its electronic ability (increase in charge carrier concentration, passivation of defect at grain boundaries 19 ) but can negatively influence stability against humidity.…”

Section: Introductionmentioning

confidence: 99%

Synergistic effect between molybdenum back contact and CIGS absorber in the degradation of solar cells

Debono,

L'Hostis,

Rebai

et al. 2023

Progress in Photovoltaics

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The stability of molybdenum (Mo) back contact and Cu (InxGa(1‐x)Se2(CIGS) absorber layers interfaces relevant for CIGS‐based solar cells was investigated using accelerated aging test, considering humidity and temperature daily variations as well as atmospheric pollution. Different configurations of sputtered Mo and co‐evaporated CIGS layers deposited on soda lime glass with or without ALD‐Al2O3 encapsulation were investigated. They were exposed for 14 days to 24 h‐cycles of temperature and humidity (25°C at 85% RH and 80°C at 30% RH) with and without solution of the pollutant salts (NaCl, Na2SO4, and (NH4)2SO4) deposited as drops on the sample to mimic marine, industrial, and rural atmospheric conditions, respectively. ALD‐Al2O3 encapsulation failed to protect the samples against the pollutants regardless of configuration. The evolution of the films was characterized by Raman spectroscopy, grazing incidence X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. Unencapsulated Mo degraded forming a mixture of oxides (MoO2, MoO3, and Mo8O23). Unencapsulated CIGS on glass substrates was not altered, whereas dark spots were visible at the surface of Mo/CIGS configurations. Further characterization evidenced that even though the Mo layer was buried, its corrosion products were formed on top of CIGS. Mo corrosion products and copper selenide, Cu2‐xSe, were identified in dark spots. Their formation and evolution were further investigated by in situ Raman spectroscopy. A speculative mechanism explaining the interplay of molybdenum and CIGS layers during aging is proposed. In place of Mo oxides, detected on the open surface of bare Mo, soluble molybdates are expected in confined environment where alkalinity locally increases. The molybdate ions may then react with sodium ions accumulated at the grain boundaries of CIGS, forming Na2MoO4. The latter could form Na2Mo2O7 during drying because of pH decrease by atmospheric CO2 adsorption. High pH in confined zone, combined with relatively high temperature, is also believed to lixiviate gallium into soluble tetragallates [Ga (OH)4]2−, which could precipitate into Ga2O3 with pH decrease leaving Ga depleted Cu2‐xSe.

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Impact of Water Ingress on Molybdenum Thin Films and Its Effect on Cu(In,Ga)Se₂ Solar Cells

Cited by 21 publications

References 28 publications

In Situ Recrystallization of Co-Evaporated Cu(In,Ga)Se2 Thin Films by Copper Chloride Vapor Treatment towards Solar Cell Applications

In Situ Recrystallization of Co-Evaporated Cu(In,Ga)Se2 Thin Films by Copper Chloride Vapor Treatment towards Solar Cell Applications

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se₂ thin‐film solar cells after exposure to thermal stress: Understanding the role of Na

Synergistic effect between molybdenum back contact and CIGS absorber in the degradation of solar cells

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Impact of Water Ingress on Molybdenum Thin Films and Its Effect on Cu(In,Ga)Se2 Solar Cells

Cited by 21 publications

References 28 publications

In Situ Recrystallization of Co-Evaporated Cu(In,Ga)Se2 Thin Films by Copper Chloride Vapor Treatment towards Solar Cell Applications

In Situ Recrystallization of Co-Evaporated Cu(In,Ga)Se2 Thin Films by Copper Chloride Vapor Treatment towards Solar Cell Applications

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se2 thin‐film solar cells after exposure to thermal stress: Understanding the role of Na

Synergistic effect between molybdenum back contact and CIGS absorber in the degradation of solar cells

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Resources

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Impact of Water Ingress on Molybdenum Thin Films and Its Effect on Cu(In,Ga)Se₂ Solar Cells

Decay mechanisms in CdS‐buffered Cu(In,Ga)Se₂ thin‐film solar cells after exposure to thermal stress: Understanding the role of Na