The effect of a post-activation annealing treatment on thin film cdte device performance

Abbas, Ali; Swanson, Drew E.; Munshi, Amit; Barth, K.; Sampath, W. S.; West, Geoff; Bowers, Jake W.; Kaminski, Piotr; Walls, John M.

doi:10.1109/pvsc.2015.7356441

Cited by 20 publications

(14 citation statements)

References 10 publications

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“…This is also observed in CdSeTe/CdTe device performance as demonstrated in this study. This is understood to be due to Cl passivating the grain boundaries and this is associated with the removal of planar defects [19]. High densities of stacking faults observed in the as deposited material are completely removed.…”

Section: Summary Of Electrical Performance Of As Deposited Cdsete/cdtmentioning

confidence: 99%

Effect of CdCl2 passivation treatment on microstructure and performance of CdSeTe/CdTe thin-film photovoltaic devices

Munshi

Kephart

Abbas

et al. 2018

Solar Energy Materials and Solar Cells

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The effects of the CdCl 2 passivation treatment on thin-film CdTe photovoltaic films and devices have been extensively studied. Recently, with an addition of CdSeTe layer at the front of the absorber layer, device conversion efficiencies in excess of 19% have been demonstrated. The effects of the CdCl 2 passivation treatment for devices using CdSeTe has not been studied previously. This is the first reported study of the effect of the treatment on the microstructure of the CdSeTe /CdTe absorber. The device efficiency is <1% for the as-deposited device but this is dramatically increased by the CdCl 2 treatment. Using Scanning Transmission Electron Microscopy (STEM), we show that the CdCl 2 passivation of CdSeTe/CdTe films results in the removal of high densities of stacking faults and increase and reorientation of grains. The CdCl 2 treatment leads to grading of the absorber CdSeTe/CdTe films by diffusion of Se between the CdSeTe and CdTe regions. Chlorine decorates the CdSeTe and CdTe grain boundaries leading to their passivation. Direct evidence for these effects is presented using STEM and Energy Dispersive X-ray Analysis (EDX) on device cross-sections prepared using focused ion beam etching. The grading of the Se in the device is quantified using EDX line scans. The comparison of CdSeTe/CdTe device microstructure and composition before and after the CdCl 2 treatment provides insights into the important effects of the process and points the way to further improvements that can be made.

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Section: Summary Of Electrical Performance Of As Deposited Cdsete/cdtmentioning

confidence: 99%

Effect of CdCl2 passivation treatment on microstructure and performance of CdSeTe/CdTe thin-film photovoltaic devices

Munshi

Kephart

Abbas

et al. 2018

Solar Energy Materials and Solar Cells

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“…At 390 C, chlorine and oxygen signatures are present at the grain boundaries. A chlorine signature along the grain boundaries is typical for CdTe passivation, 20 but the strong corresponding oxygen signal is atypical. At 420 C, no significant change in the chlorine signature was observed, but large voids begin to form near select grain boundaries with corresponding oxygen signals.…”

Section: Identifying Loss Locationmentioning

confidence: 99%

“…In CdTe chloride passivation, it has been theorized that chlorine travels down the grain boundaries in an elemental state and preferentially accumulates there. 20,32 The chlorine can remove stacking faults from within the CdTe grains and may passivate the grain boundaries by filling tellurium vacancies, effectively making the grain boundaries less p-type. 23 This can affect both transport and recombination.…”

Section: Identifying Loss Locationmentioning

confidence: 99%

“…Chlorine loss mechanisms have been reported in the CdTe literature at elevated temperatures. 20 Cross-sectional cathodoluminescence images of asdeposited and 420 C CdCl 2 passivation CdZnTe absorbers are presented in Fig. 10.…”

Section: Identifying Loss Locationmentioning

confidence: 99%

“…CdCl 2 has been reported to have various effects on CdTe including recrystallization, grain growth, stacking fault removal, and grain boundary passivation by putting chlorine on tellurium vacancies. [20][21][22][23] However, initial attempts at CdCl 2 passivation of CdMgTe and CdZnTe have revealed reductions in the bandgap of both absorbers during CdCl 2 passivation. 16,18,19 This work aims to study this CdCl 2 -induced degradation and develop a more comprehensive understanding of the reactions occurring.…”

Section: Introductionmentioning

confidence: 99%

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CdCl2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells

Swanson

Reich

Abbas

et al. 2018

Journal of Applied Physics

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As single-junction silicon solar cells approach their theoretical limits, tandems provide the primary path to higher efficiencies. CdTe alloys can be tuned with magnesium (CdMgTe) or zinc (CdZnTe) for ideal tandem pairing with silicon. A II-VI/Si tandem holds the greatest promise for inexpensive, high-efficiency top cells that can be quickly deployed in the market using existing polycrystalline CdTe manufacturing lines combined with mature silicon production lines. Currently, all high efficiency polycrystalline CdTe cells require a chloride-based passivation process to passivate grain boundaries and bulk defects. This research examines the rich chemistry and physics that has historically limited performance when extending Cl treatments to polycrystalline 1.7-eV CdMgTe and CdZnTe absorbers. A combination of transmittance, quantum efficiency, photoluminescence, transmission electron microscopy, and energy-dispersive X-ray spectroscopy clearly reveals that during passivation, Mg segregates and out-diffuses, initially at the grain boundaries but eventually throughout the bulk. CdZnTe exhibits similar Zn segregation behavior; however, the onset and progression is localized to the back of the device. After passivation, CdMgTe and CdZnTe can render a layer that is reduced to predominantly CdTe electro-optical behavior. Contact instabilities caused by inter-diffusion between the layers create additional complications. The results outline critical issues and paths for these materials to be successfully implemented in Si-based tandems and other applications.

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Back contacts materials used in thin film CdTe solar cells—A review

Hall

Lamb

Irvine

2021

Energy Science & Engineering

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The effect of a post-activation annealing treatment on thin film cdte device performance

Cited by 20 publications

References 10 publications

Effect of CdCl2 passivation treatment on microstructure and performance of CdSeTe/CdTe thin-film photovoltaic devices

Effect of CdCl2 passivation treatment on microstructure and performance of CdSeTe/CdTe thin-film photovoltaic devices

CdCl2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells

Back contacts materials used in thin film CdTe solar cells—A review

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