Selective Growth of CdTe on Nano-patterned CdS via Close-Space Sublimation

Aguirre, Brandon Adrian; Zubía, David; Ordonez, Rafael; Anwar, Farhana; Prieto, Heber; Sanchez, Carlos Anthony; Salazar, Maria; Pimentel, Alejandro A.; Michael, Joseph R.; Zhou, Xiaowang; McClure, Joshua P.; Nielson, Gregory N.; Cruz‐Campa, Jose Luis

doi:10.1007/s11664-014-3104-7

Cited by 15 publications

(4 citation statements)

References 13 publications

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“…Past efforts (Aguirre et al, 2014) (Cruz-Campa et al, 2012) (Zubia et al, 2007) have focused on reducing defects during the fabrication of the epilayers, although the fundamental mechanisms of defect formation are not well understood. Experimental studies have shown that careful preparation of the substrate surface termination (Myers et al, 1983) and the orientation of the substrate (Smith et al, 2000) (Sarney & Brill, 2004) (Terheggen et al, 2003) can greatly influence the microstructure and the quality of the heteroepitaxial film.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of CdTe / CdS Heteroepitaxy - Effect of Substrate Orientation

Chavez¹,

Zhou²,

Almeida³

et al. 2016

JMSR

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Molecular dynamics simulations were used to catalogue atomic scale structures of CdTe films grown on eight wurtzite (wz) and zinc-blende (zb) CdS surfaces. Polytypism, grain boundaries, dislocations and other film defects were detected. Dislocation lines were distributed in three distinct ways. For the growths on the wz {0001} and zb {111} surfaces, dislocations were found throughout the epilayers and formed a network at the interface. The dislocations within the films grown on the wz {1 100}, wz {112 0}, zb {1 10}, zb {010}, and zb { 1 } surfaces formed an interface network and also threaded from the interface towards the film's surface. In contrast, the growth on the zb {112 } surface only had dislocations localized to the interface. This film exhibited a different orientation from the substrate to reduce the lattice mismatch strain energies, and therefore, its misfit dislocation density. Our study indicates that the substrate orientation could be utilized to modify the morphology of dislocation networks in lattice mismatched multi-layered systems.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of CdTe / CdS Heteroepitaxy - Effect of Substrate Orientation

Chavez¹,

Zhou²,

Almeida³

et al. 2016

JMSR

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“…Still, improving the quality of 519 this interface may prove important to voltage increases 520 above the current state of the art. Adding a patterned, 521 insulating oxide with nanoscale CdS contacts is one 522 way of creating single-crystal CdTe islands, and may 523 improve growth of the CdTe by preventing disloca-524tions and other defects in the CdTe absorber[29,30].…”

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confidence: 99%

Band alignment of front contact layers for high-efficiency CdTe solar cells

Kephart

McCamy

et al. 2016

Solar Energy Materials and Solar Cells

167

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Resistive oxide materials play an important role in the front contact of CdTe solar cells. The highresistance transparent (HRT) or "buffer" layer has been used extensively in CdTe thin-film photovoltaics to enable a reduction in CdS thickness while maintaining near-maximum device voltage and fill factor. SnO 2and ZnO-based alloys were tested as HRT layers on a fluorine-doped tin oxide transparent conducting oxide. SnO 2-based alloy HRT layers were deposited via atmospheric pressure chemical vapor deposition (APCVD). Alloying ZnO with MgO to create Mg x Zn 1−x O (MZO) via radio-frequency sputter deposition was explored as a way to reduce the electron affinity of ZnO HRT layers. To fully understand the behavior of these materials, many devices were fabricated with either no CdS layer, a sublimated CdS layer, or a sputtered, oxygenated CdS layer. MZO layers resulted in high open-circuit voltage and device efficiency even with the complete elimination of the CdS layer. In both HRT systems, controlling electron affinity to optimize front contact band alignment is an important consideration. Band measurements using photoelectron spectroscopy and synchrotron techniques correlate band alignment measurements with efficiency parameters in the design of HRT and CdS layers.

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“…This procedure results in arrays of isolated micro‐CdTe cells grown on a polycrystalline CdS film as shown in Figure . More details about the fabrication of the microcells are described elsewhere .…”

Section: Methodsmentioning

confidence: 99%

Mapping photovoltaic performance with nanoscale resolution

Kutes

Aguirre

Bosse

et al. 2015

Progress in Photovoltaics

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Photo-conductive AFM spectroscopy ('pcAFMs') is proposed as a high-resolution approach for investigating nanostructured photovoltaics, uniquely providing nanoscale maps of photovoltaic (PV) performance parameters such as the short circuit current, open circuit voltage, maximum power, or fill factor. The method is demonstrated with a stack of 21 images acquired during in situ illumination of micropatterned polycrystalline CdTe/CdS, providing more than 42 000 I/V curves spatially separated by~5 nm. For these CdTe/CdS microcells, the calculated photoconduction ranges from 0 to 700 picoSiemens (pS) upon illumination with~1.6 suns, depending on location and biasing conditions. Mean short circuit currents of 2 pA, maximum powers of 0.5 pW, and fill factors of 30% are determined. The mean voltage at which the detected photocurrent is zero is determined to be 0.7 V. Significantly, enhancements and reductions in these more commonly macroscopic PV performance metrics are observed to correlate with certain grains and grain boundaries, and are confirmed to be independent of topography. These results demonstrate the benefits of nanoscale resolved PV functional measurements, reiterate the importance of microstructural control down to the nanoscale for 'PV devices, and provide a widely applicable new approach for directly investigating PV materials.

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Selective Growth of CdTe on Nano-patterned CdS via Close-Space Sublimation

Cited by 15 publications

References 13 publications

Molecular Dynamics Simulations of CdTe / CdS Heteroepitaxy - Effect of Substrate Orientation

Molecular Dynamics Simulations of CdTe / CdS Heteroepitaxy - Effect of Substrate Orientation

Band alignment of front contact layers for high-efficiency CdTe solar cells

Mapping photovoltaic performance with nanoscale resolution

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