Inclusions Elimination and Resistivity Restoration of CdTe:Cl Crystals by Two-Step Annealing

Bugár, M.; Belas, E.; Grill, R.; Procházka, Jan; Uxa, Štěpán; Hlı́dek, P.; Franc, J.; Fesh, R.; Höschl, P.

doi:10.1109/tns.2011.2159394

Cited by 24 publications

(16 citation statements)

References 18 publications

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“…It seems that the kinetics of CdTe material formation has this inherent property, and this has been confirmed by heat-treating these CdTe materials in Cd and Cl environment [40][41][42] by numerous researchers in the past during development of high resistivity CdTe for X-ray and γ-ray detectors. There is also excellent work showing that these Te precipitates are completely removed when these CdTe crystals are grown or treated in the presence of Cd or Cl [41]. The CdTe PV researchers need to use these findings in order to fully understand the CdCl 2 treatment.…”

Section: Te Precipitation In Cdtementioning

confidence: 86%

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Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding

2014

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Cadmium chloride treatment is a key processing step identified in the late 1970s to drastically improve the solar to electric conversion efficiency of CdS/CdTe thin film solar cells. Although a large body of experimental results are available to date, this process is yet to be understood even after three decades of research. This paper reviews the experimental results available, presents some new clues leading to improved understanding and suggests key research areas necessary to fully understand this crucial processing step. Improved understanding will lead to further increase in conversion efficiency of CdS/CdTe solar cells well beyond 20%.

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Section: Te Precipitation In Cdtementioning

confidence: 86%

“…Review of a large body of CdTe growth techniques reveals that Te precipitation in CdTe is a common issue [40][41][42]. Even melt-growth technique for growing bulk CdTe, show severe precipitation of Te in CdTe crystals.…”

Section: Te Precipitation In Cdtementioning

confidence: 99%

Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding

2014

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“…In the c-and X-ray detectors research work based on insulating and semi-insulating CdTe, it is well known that Te precipitation is common in CdTe material, irrespective of the growth technique [22][23][24][25][26]. It is also known that treatment similar to CdCl 2 , removes these precipitated Te [27].…”

Section: Discussionmentioning

confidence: 99%

Improvement of composition of CdTe thin films during heat treatment in the presence of CdCl2

Dharmadasa

Echendu

Fauzi

et al. 2016

J Mater Sci: Mater Electron

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CdCl 2 treatment is a crucial step in development of CdS/CdTe solar cells. Although this processing step has been used over a period of three decades, full understanding is not yet achieved. This paper reports the experimental evidence for improvement of composition of CdTe layers during CdCl 2 treatment. This investigation makes use of four selected analytical techniques; Photoelectro-chemical (PEC) cell, X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM). CdTe layers used were electroplated using three Cd precursors; CdSO 4 , Cd(NO 3 ) 2 and CdCl 2 . Results show the improvement of stoichiometry of CdTe layers during CdCl 2 treatment through chemical reaction between Cd from CdCl 2 and elemental Te that usually precipitate during CdTe growth, due to its natural behaviour. XRD and SEM results show that the low-temperature (*85°C) electroplated CdTe layers consist of *(20-60) nm size crystallites, but after CdCl 2 treatment, the layers show drastic recrystallisation with grains becoming a few microns in size. These CdCl 2 treated layers are then comparable to high temperature grown CdTe layers by the size of grains.

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“…Out of the two elements, Cd and Te in CdTe, Te is the easiest element to discharge first and deposit during electroplating (E o for Te is +0.593 V, and E o for Cd is -0.403 V). Therefore Te can be precipitated [12][13][14] within the layer or form a thin layer of Cd x TeO y on the surface [15]. Hence, most of the as-deposited CdTe layers have Te-rich nature and therefore T 1 , T 2 and T 3 trap levels are dominant.…”

Section: Effects On Materialsmentioning

confidence: 99%

Effects of CdCl2 treatment on deep levels in CdTe and their implications on thin film solar cells: a comprehensive photoluminescence study

Dharmadasa

Echendu

Fauzi

et al. 2015

J Mater Sci: Mater Electron

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This work is aimed at studying defect level distributions in the bandgap of CdTe thin films, used for solar cell development. In particular, the effects of CdCl 2 treatment on the defect levels are the main objectives of this research. Four different CdTe thin films were electroplated using three different Cd-precursors (CdSO 4 , Cd(NO 3 ) 2 and CdCl 2 ), and bulk CdTe wafers purchased from industry (Eagle Pitcher and University Wafers in US) were studied using low temperature photoluminescence. The finger prints of defects, 0.55 eV below the conduction band down to the valence band edge were investigated. In all of the CdTe layers, four electron trap levels were observed with varying intensities but at very similar energy positions, indicating that the origin of these defects are mainly from native defects. CdCl 2 treatment and annealing eliminates two defect levels and the mid-gap recombination centres are reduced drastically by this processing step. The optical bandgap of all four as-deposited CdTe layers is ~1.50 eV, and reduces to ~1.47 eV after CdCl 2 treatment. The material grown using the CdCl 2 precursor seems to produce CdTe material with the cleanest bandgap, most probably due to the built-in CdCl 2 treatment while growing the material.

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Inclusions Elimination and Resistivity Restoration of CdTe:Cl Crystals by Two-Step Annealing

Cited by 24 publications

References 18 publications

Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding

Review of the CdCl2 Treatment Used in CdS/CdTe Thin Film Solar Cell Development and New Evidence towards Improved Understanding

Improvement of composition of CdTe thin films during heat treatment in the presence of CdCl2

Effects of CdCl2 treatment on deep levels in CdTe and their implications on thin film solar cells: a comprehensive photoluminescence study

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