Atomistic modeling of energy band alignment in CdSeTe surfaces

Shah, Akash; Munshi, Amit; Nicholson, Anthony P.; Thiyagarajan, Aanand; Pozzoni, Umberto M.; Sampath, Walajabad S.

doi:10.1016/j.apsusc.2020.148762

Cited by 9 publications

(8 citation statements)

References 40 publications

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“…Similar conclusions have been drawn for the reconstructed surface in other studies. All the CdSe 0.25 Te 0.75 surface relaxation were done using one‐probe model described by Shah et al [ 20 ]…”

Section: Computational Detailsmentioning

confidence: 99%

“…It is well known that due to localization of the Cd‐4d and Te‐5p bands, DFT tends to underestimate the bandgaps of the CdTe and CdSe x Te 1– x alloys. Shah et al in previous study [ 20 ] reported that a semiempirical DFT‐1/2 correction scheme [ 21 ] could be utilized to obtain the correct bandgap energy values for bulk CdSe x Te 1– x alloy. A DFT‐1/2 correction scheme was used in this work to calculate the electronic properties of the relaxed Se‐graded CdSe 0.25 Te 0.75 /CdTe S–I model.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Similar conclusions have been drawn for the reconstructed surface in other studies. All the CdSe 0.25 Te 0.75 surface relaxation were done using one-probe model described by Shah et al [20] Due to the lattice mismatch between CdSe x Te 1-x and CdTe layers, a 1.49%, 2.24%, and 1.49% interface strain was recorded between ungraded CdSe 0.25 Te 0.75 /CdTe interfaces for the polar (100), (111), and nonpolar (110) plane orientations, respectively. As these interfaces were formed after relaxing the CdSe 0.25 Te 0.75 surfaces, hereon the models are referred to surface-interface (S-I) models.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Swanson et al and others in their work have suggested that the bandgap of Se-alloyed CdTe absorber could be altered based on the Se composition. [20,32,33] In this regard, devices with two different source charges viz CST-20 (molar fraction of CdSe is 20%) and CST-40 (molar fraction of CdSe is 40%) were used to make higher and lower bandgap CdSeTe absorbers. Based on the analyses presented earlier, it was further predicted that a bilayer of CST 40/CdTe absorberbased (with smaller bandgap CdSeTe absorber grown from CST 40 absorber material in front) PV devices would have better electron reflector-type effect and therefore would lead to higher efficiencies.…”

Section: Energy Band Alignment From Density Functional Theorymentioning

confidence: 99%

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Understanding the Role of CdTe in Polycrystalline CdSe_xTe_1–x/CdTe‐Graded Bilayer Photovoltaic Devices

et al. 2021

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Grading of bandgap by alloying CdTe with selenium to form a CdSe x Te1–x /CdTe‐graded bilayer device has led to a device efficiency over 19%. A CdSe x Te1–x absorber would increase the short‐circuit current due to its lower bandgap but at the expense of open‐circuit voltage. It has been demonstrated that adding a CdTe layer at the back of such a CdSe x Te1–x film reduces the voltage deficit caused by the lower bandgap of absorber from selenium alloying while maintaining the higher short‐circuit current. This leads to a photovoltaic device that draws advantage from both materials with an efficiency greater than either of them. Herein, a detailed account using device data, ultraviolet photoelectron spectroscopy, electron microscopy, and first‐principles density functional theory modeling is provided, which shows that CdTe acts as an electron reflector for CdSe x Te1–x .

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Section: Computational Detailsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: Energy Band Alignment From Density Functional Theorymentioning

confidence: 99%

See 2 more Smart Citations

Understanding the Role of CdTe in Polycrystalline CdSe_xTe_1–x/CdTe‐Graded Bilayer Photovoltaic Devices

et al. 2021

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“…Several studies in the past using experimental and theoretical techniques have explored the electronic properties of bulk CdSe x Te 1– x . − However, the combined effects of Se and Cl at the CdTe grain boundaries on the electronic structure and charge carrier transport behaviors are unknown. In this work, we report the Se and Cl atomic scale composition and electronic structure of the grain boundaries through NanoSIMS and DFT simulations, respectively.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Copassivation Effect of Cl and Se for CdTe Grain Boundaries

Shah

Nicholson

Fiducia

et al. 2021

ACS Appl. Mater. Interfaces

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Chlorine passivation treatment of cadmium telluride (CdTe) solar cells improves device performance by assisting electron–hole carrier separation at CdTe grain boundaries. Further improvement in device efficiency is observed after alloying the CdTe absorber layer with selenium. High-resolution secondary ion mass spectroscopy (NanoSIMS) imaging has been used to determine the distribution of selenium and chlorine at the CdTe grain boundaries in a selenium-graded CdTe device. Atomistic modeling based on density functional theory (DFT-1/2) further reveals that the presence of selenium and chlorine at an exemplar (110)/(100) CdTe grain boundary passivates critical acceptor defects and leads to n-type inversion at the grain boundary. The defect state analysis provides an explanation for the band-bending effects observed in the energy band alignment results, thereby elucidating mechanisms for high efficiencies observed in Se-alloyed and Cl-passivated CdTe solar cells.

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Influence of structural defects on charge density waves in 1T-TaS2

et al. 2023

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The influence of intrinsic defects of 1T-TaS2 on charge density waves (CDWs) is studied using scanning tunneling microscopy and spectroscopy (STM, STS), angle-resolved photoelectron spectroscopy (ARPES), and density functional theory (DFT). We identify several types of structural defects and find that most have a local character limited to a single CDW site, with a single exception which effectively behaves as a dopant, leading to band-bending and affecting multiple neighboring sites. While only one type of defect can be observed by STM topographic imaging, all defects are easily resolved in STS mapping. Our results indicate modulation of the Mott band gap commensurate with the CDW and breaking of the three-fold symmetry of electronic states. DFT calculations (with included Coulomb interactions) are used to investigate the electronic structure, focusing on both sulfur vacancy and oxygen-sulfur substitution. The sulfur vacancy system, characterized with a metallic behavior, is identified as the origin of one of the experimentally observed defects. Additionally, the effect of oxidation of 1T-TaS2 depends on the substitution site, leading to the heterogeneity of electronic properties.

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Atomistic modeling of energy band alignment in CdSeTe surfaces

Cited by 9 publications

References 40 publications

Understanding the Role of CdTe in Polycrystalline CdSe_xTe_1–x/CdTe‐Graded Bilayer Photovoltaic Devices

Understanding the Role of CdTe in Polycrystalline CdSe_xTe_1–x/CdTe‐Graded Bilayer Photovoltaic Devices

Understanding the Copassivation Effect of Cl and Se for CdTe Grain Boundaries

Influence of structural defects on charge density waves in 1T-TaS2

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Atomistic modeling of energy band alignment in CdSeTe surfaces

Cited by 9 publications

References 40 publications

Understanding the Role of CdTe in Polycrystalline CdSexTe1–x/CdTe‐Graded Bilayer Photovoltaic Devices

Understanding the Role of CdTe in Polycrystalline CdSexTe1–x/CdTe‐Graded Bilayer Photovoltaic Devices

Understanding the Copassivation Effect of Cl and Se for CdTe Grain Boundaries

Influence of structural defects on charge density waves in 1T-TaS2

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Product

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Understanding the Role of CdTe in Polycrystalline CdSe_xTe_1–x/CdTe‐Graded Bilayer Photovoltaic Devices

Understanding the Role of CdTe in Polycrystalline CdSe_xTe_1–x/CdTe‐Graded Bilayer Photovoltaic Devices