Transient Metastable Behaviour in Highly Efficient MZO/CdSeTe/CdTe Thin Film Solar Cells

Togay, Mustafa; Greenhalgh, Rachael; Shimpi, Tushar; Walajabad, S Sampath; Barth, K.; Walls, John M.; Bowers, Jake W.

doi:10.1109/pvsc43889.2021.9518997

Cited by 3 publications

(5 citation statements)

References 18 publications

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“…We have previously reported on the behavior of MZO/ CdSeTe/CdTe devices with 11 wt% of MgO content in the MZO layer [4]. Here, we report on the metastable behavior of PV parameters observed in devices with MgO content of 5 wt%, 8 wt%, 11 wt%, 14 wt%, and 21 wt% as measured in different laboratories under different ambient conditions.…”

mentioning

confidence: 82%

“…However, modifying the cell architecture introduces more complexity in understanding the factors that limit performance and has also introduced detrimental characteristics in the PV device, including stability issues as well as transient metastable behavior due to prior exposure history (such as temperature, climate, and irradiance). These characteristics have been observed after introducing the MZO buffer layer [4]. Furthermore, for consistent comparisons between different laboratories when using different PV materials and architectures, it is advisable to adopt a common preconditioning procedure in order to measure and interpret reliable performance data.…”

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confidence: 95%

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Transient Metastable Behavior Caused by Magnesium-Doped Zinc Oxide Emitters in CdSeTe/CdTe Solar Cells

Togay

Greenhalgh

Fiducia

et al. 2023

IEEE J. Photovoltaics

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Metastable behavior in highly efficient MZO/CdSeTe/ CdTe solar cells has been reported previously. Different preconditioning procedures have been studied that are used to recover the performance of the devices. 11 wt% of MgO content in the MZO layer has shown to give optimized photovoltaic parameters in the device compared to other MZO compositions. J-V characteristics before preconditioning of the devices with higher MgO content show an "S" shaped behavior, which is removed during preconditioning. However, this recovery remained only for 3 days while the devices were stored under vacuum in the dark. Temperaturedependent J-V and capacitance measurements before and after preconditioning revealed the presence of recombination centers and defect levels at the MZO/absorber interface. Previous studies have shown degradation of MZO occurring if the layer is exposed to ambient atmosphere. Hall effect measurements on the MZO films showed no significant changes after any preconditioning or CdCl 2 treatment. Secondary-ion mass spectrometry images show diffusion of oxygen from the MZO layer into the CdSeTe region after CdCl 2 treatments. This likely enables the MZO to function as a buffer layer since it will increase the carrier concentration due to the formation of oxygen vacancies. As-deposited MZO thin films are insulating. However, the oxygen vacancies in the MZO layer also increase its reactivity and instability.

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confidence: 82%

mentioning

confidence: 95%

Transient Metastable Behavior Caused by Magnesium-Doped Zinc Oxide Emitters in CdSeTe/CdTe Solar Cells

Togay

Greenhalgh

Fiducia

et al. 2023

IEEE J. Photovoltaics

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“…Others have noted that the S-kink in the MZO devices can also be due to metastability in the MZO due to the formation of MgO during processing. 27,28 Thus, both mechanisms depend on device processing, especially when CdCl 2 activation is done in air. We note that the devices reported here were CdCl 2 activated in air and illuminated with an LED solar simulator with a 400 nm low wavelength cutoff but do not show any S-kink-like behavior until the bandgap of the emitter is 4.10 eV.…”

Section: Ga O Gmentioning

confidence: 99%

“…For some devices, the S-kink appears to be related to the carrier concentration and Fermi level position in the MZO even when only a small positive CBO exists , when the doping level in MZO is controlled by oxygen vacancy concentration. Others have noted that the S-kink in the MZO devices can also be due to metastability in the MZO due to the formation of MgO during processing. , Thus, both mechanisms depend on device processing, especially when CdCl 2 activation is done in air. We note that the devices reported here were CdCl 2 activated in air and illuminated with an LED solar simulator with a 400 nm low wavelength cutoff but do not show any S-kink-like behavior until the bandgap of the emitter is 4.10 eV.…”

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confidence: 99%

Indium Gallium Oxide Emitters for High-Efficiency CdTe-Based Solar Cells

Jamarkattel

Phillips

Subedi

et al. 2022

ACS Appl. Energy Mater.

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There are limited choices for front-surface, electron-selective contacts (emitters) for CdTe solar cells, thus hindering scientific and technical development. Here we investigate the photovoltaic performance of devices fabricated with (In x Ga 1−x ) 2 O 3 (IGO) emitters with varying In-to-Ga ratios prepared by cosputtering. In agreement with predictions, an IGO emitter with a 4.03 eV bandgap (x = 0.36) allowed fabrication of devices with efficiencies of 16%. Increasing the performance to higher values will be enabled by increasing the transmission through the IGO-coated substrate and decreasing the bulk and back interface recombination. These findings demonstrate IGO materials as effective emitters in highefficiency CdTe-based solar cells.

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“…The measurement follows 3 important steps; the contact check, the sheet resistance measurement, and the Hall resistance measurement in order to extract reliable and accurate carrier concentration and mobility. The details of the measurements steps have been provided elsewhere [10].…”

Section: B Pdl Hall Effect Measurementsmentioning

confidence: 99%

Ga-doping of MZO in CdSeTe/CdTe Thin Film Solar Cells

Togay

Shimpi

Walajabad

et al. 2022

2022 IEEE 49th Photovoltaics Specialists Conference (PVSC)

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Metastable effects in high efficiency MZO/CdSeTe/CdTe solar cells have been studied in an attempt to recover the device performance. Devices with the MZO buffer layer have shown an `S` shaped behaviour in the J-V characteristics before any preconditioning. This is removed after light soaking under 1000 Wm -2 at 25 °C. However, this recovery remained only for a short period of time while the devices were stored under vacuum in the dark. Recent studies with Ga doping of the buffer MZO has shown the removal of this metastability in the J-V characteristics of CdTe devices can be achieved without light soaking. A significant improvement in conductivity and Hall signal has been measured with Ga doped MZO layers compared to previously measured MZO films. However, a gradual decrease in the Hall signal has been observed over time after films were light soaked and removed from the desiccator.

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Transient Metastable Behaviour in Highly Efficient MZO/CdSeTe/CdTe Thin Film Solar Cells

Cited by 3 publications

References 18 publications

Transient Metastable Behavior Caused by Magnesium-Doped Zinc Oxide Emitters in CdSeTe/CdTe Solar Cells

Transient Metastable Behavior Caused by Magnesium-Doped Zinc Oxide Emitters in CdSeTe/CdTe Solar Cells

Indium Gallium Oxide Emitters for High-Efficiency CdTe-Based Solar Cells

Ga-doping of MZO in CdSeTe/CdTe Thin Film Solar Cells

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