Sputter-Deposited Oxides for Interface Passivation of CdTe Photovoltaics

Kephart, Jason M.; Kindvall, Anna; Williams, Desiree D.; Kuciauskas, Darius; Dippo, P.; Munshi, Amit; Sampath, Walajabad S.

doi:10.1109/jphotov.2017.2787021

IEEE J. Photovoltaics

2018

DOI: 10.1109/jphotov.2017.2787021

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Sputter-Deposited Oxides for Interface Passivation of CdTe Photovoltaics

Jason M. Kephart

Anna Kindvall

Desiree D. Williams

et al.

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Cited by 97 publications

(71 citation statements)

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“…In CdTe solar cells, back‐contact recombination velocity S back > 10 5 cm s −1 and high recombination can reduce carrier lifetimes, radiative efficiency, and power conversion efficiency. To develop passivated contacts, Kephart et al investigated CdSe x Te 1− x passivation with Al 2 O 3 . Alumina passivation reduces interface recombination velocity S int < 100 cm s −1 and correspondingly increases carrier lifetimes to more than 200 ns in polycrystalline double heterostructures (DHs) .…”

mentioning

confidence: 99%

“…The polycrystalline DH layer stack consisted of glass/Al 2 O 3 /CdSe x Te 1− x /Al 2 O 3 . Corning 0.7 mm‐thick 7059 glass was used as the substrate.…”

mentioning

confidence: 99%

“…After the first CdCl 2 treatment, films were then rinsed for 10–15 s in MeOH before growing the final, 20 nm‐thick alumina layer. Similar to Kephart et al, a final CdCl 2 treatment was required at a lower temperature (400 °C for 10 min) to attain the highest carrier lifetimes. The use of O 2 during this final CdCl 2 treatment was inconclusive, unlike the use of oxygen during the first CdCl 2 treatment.…”

mentioning

confidence: 99%

“…To develop passivated contacts, Kephart et al investigated CdSe x Te 1Àx passivation with Al 2 O 3 . [16] Alumina passivation reduces interface recombination velocity S int < 100 cm s À1 and correspondingly increases carrier lifetimes to more than 200 ns in polycrystalline double heterostructures (DHs). [17] The passivation mechanisms are related to interface oxides [18] and charges.…”

mentioning

confidence: 99%

“…The polycrystalline DH layer stack consisted of glass/Al 2 O 3 / CdSe x Te 1Àx /Al 2 O 3 . [16] Corning 0.7 mm-thick 7059 glass was used as the substrate. Alumina layers were deposited by e-beam evaporation of 99.99% alumina (Kurt J. Lesker Company) chunks (1-3 mm) at a growth rate of 0.2 nm s À1 .…”

mentioning

confidence: 99%

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Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

Kuciauskas

Moseley

Ščajev

et al. 2019

Physica Rapid Research Ltrs

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CdTe‐based photovoltaics is a rapidly developing energy technology with one of the lowest levelized costs of electricity. But nonradiative Shockley–Read–Hall (SRH) recombination limits the efficiency of CdTe solar cells. Partial mitigation of bulk and grain‐boundary SRH recombination was achieved by alloying CdTe with Se, and CdSexTe1−x absorbers are used in high‐efficiency solar cells. Recently, interface recombination was significantly reduced with alumina passivation, but other properties of Al2O3/CdSexTe1−x/Al2O3 heterostructures have not yet been investigated. Herein, further progress in understanding and developing polycrystalline heterostructures with x = 0.2 is reported. It is shown that external photoluminescence quantum yield is increased to 0.2%, quasi‐Fermi‐level splitting to 950 mV, minority carrier lifetimes to 750 ns, and mobility to 100 cm2 Vs−1. Such polycrystalline CdSexTe1−x electronic characteristics match or exceed CdTe single‐crystal properties. The resulting charge‐carrier diffusion length of ≈14 μm is several times greater than the absorber thickness in test structures and in typical CdTe solar cells. Herein, with passivation and absorbers, polycrystalline CdSeTe solar cell open‐circuit voltage is increased from the current 76% of the Shockley–Queisser limit to 82%, or close to 1 V is reported.

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mentioning

confidence: 99%

“…The polycrystalline DH layer stack consisted of glass/Al 2 O 3 /CdSe x Te 1− x /Al 2 O 3 . Corning 0.7 mm‐thick 7059 glass was used as the substrate.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

Kuciauskas

Moseley

Ščajev

et al. 2019

Physica Rapid Research Ltrs

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Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth‐Resolved Muon Spin Spectroscopy

Alberto

Vilão

Ribeiro

et al. 2022

Adv Materials Inter

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As devices become smaller and more complex, the interfaces between adjacent materials become increasingly important and are often critical to device performance. An important research goal is to improve the interface between the absorber and the window layer by inserting buffer layers to adjust the transition. Depth‐resolved studies are key for a fundamental understanding of the interface. In the present experiment, the interface between the chalcopyrite Cu(In,Ga)Se2 absorber and various buffer layers are investigated using low‐energy muon spin rotation (μSR) spectroscopy. Depth resolution in the nm range is achieved by implanting the muons with different energies so that they stop at different depths in the sample. Near the interface, a region about 50 nm wide is detected where the lattice is more distorted than further inside the absorber. The distortion is attributed to the long‐range strain field caused by defects. These measurements allow a quantification of the corresponding passivation effect of the buffer layer. Bath‐deposited cadmium sulfide provides the best defect passivation in the near interface region, in contrast to the dry‐deposited oxides, which have a much smaller effect. The experiment demonstrates the great potential of low energy μSR spectroscopy for microscopic interfacial studies of multilayer systems.

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Microstructural Passivation of Patterned Al₂O₃ Back Contacts on CdS/CdTe Solar Cells

Roy,

Mamun,

Lee

et al. 2024

Adv Materials Inter

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Patterned aluminum oxide (Al2O3) back contact on cadmium telluride (CdTe) solar cells can effectively mitigate the loss of the majority carriers while retaining the passivation benefits for minority carriers. This study investigates the impact of the point‐contact geometry on cell performance, where the spacing of the microholes is systematically varied at a constant microhole diameter (≈16 µm). Microhole arrays are created on an evaporated Al2O3 layer (≈30 nm) on CdTe using laser‐beam lithography and selective wet etching processes. Comparative analysis indicates a significant decrease in fill factor (FF) and short‐circuit current (ISC) when the contact fraction falls below 30%, likely due to the Al2O3 barrier impeding majority carriers. Above this fraction, FF and ISC are comparable to those of baseline CdTe cells without Al2O3. Open‐circuit voltage (VOC) shows a gradual decrease as Al2O3 coverage is reduced but exhibits a slight increase (<15 mV) when the contact fraction exceeds 30%. Cathodoluminescence (CL) characterization reveals that significantly improved radiative recombination occurs within the CdTe grain bulk with Al2O3, whereas this effect on grain boundaries is minimal. The findings imply complex local carrier dynamics in the patterned back‐contact region, closely tied to the microstructural properties of CdTe‐based solar cells.

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Sputter-Deposited Oxides for Interface Passivation of CdTe Photovoltaics

Cited by 97 publications

References 22 publications

Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth‐Resolved Muon Spin Spectroscopy

Microstructural Passivation of Patterned Al₂O₃ Back Contacts on CdS/CdTe Solar Cells

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Sputter-Deposited Oxides for Interface Passivation of CdTe Photovoltaics

Cited by 97 publications

References 22 publications

Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

Radiative Efficiency and Charge‐Carrier Lifetimes and Diffusion Length in Polycrystalline CdSeTe Heterostructures

Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth‐Resolved Muon Spin Spectroscopy

Microstructural Passivation of Patterned Al2O3 Back Contacts on CdS/CdTe Solar Cells

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Microstructural Passivation of Patterned Al₂O₃ Back Contacts on CdS/CdTe Solar Cells