Development of back contacts for CdTe thin film solar cells deposited on flexible foil substrates

Hodges, Deidra; Palekis, Vasilios; Shen, D.; Singh, Kartikay; Bhandaru, S.; Stefanakos, Elias K.; Morel, D.L.; Ferekides, C.S.

doi:10.1109/pvsc.2009.5411404

Cited by 9 publications

(7 citation statements)

References 11 publications

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“…Also, because Mo can be obtained in high purity, problems of dopant impurities diffusing into the CdTe at elevated temperatures are reduced. In addition the ready availability of pure Mo reduces the possibility of dopant impurities diffusing into the CdTe at elevated temperatures, as it occurs in other substrates, such as stainless steel (SS) [32,43,44].…”

Section: Superstrate and Substrate Structures In Thin Film Solar Cellsmentioning

confidence: 99%

“…Alternatively, a lower work function, and heavily doped p-type semiconductor is placed between the CdTe and metallic contact, serving as an interlayer. Such measures, referred to as back surface field (BSF) increases cell performance by reducing the recombination at the back contact, leading to improved V oc and reduced series resistance [44,46]. Some commonly used metals and semiconductors, either alone or in combination with others (especially Cu), as back contact layers on glass include C : Cu, Cu, Au, Ag, Sb, Ni, Mo, Te, ZnTe, Sb 2 Te 3 , As 2 Te 3 , CuTe, and HgTe, [6,12,24,26,29,32,44,[47][48][49] When some of these were used in flexible cells, improved cell performances were observed.…”

Section: Superstrate and Substrate Structures In Thin Film Solar Cellsmentioning

confidence: 99%

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Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

Aliyu

Islam

Hamzah

et al. 2012

International Journal of Photoenergy

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This study investigates the key issues in the fabrication of CdTe solar cells on metallic substrates, their trends, and characteristics as well as effects on solar cell performance. Previous research works are reviewed while the successes, potentials, and problems of such technology are highlighted. Flexible solar cells offer several advantages in terms of production, cost, and application over glass-based types. Of all the metals studied as substrates for CdTe solar cells, molybdenum appears the most favorable candidate, while close spaced sublimation (CSS), electrodeposition (ED), magnetic sputtering (MS), and high vacuum thermal evaporation (HVE) have been found to be most common deposition technologies used for CdTe on metal foils. The advantages of these techniques include large grain size (CSS), ease of constituent control (ED), high material incorporation (MS), and low temperature process (MS, HVE, ED). These invert-structured thin film CdTe solar cells, like their superstrate counterparts, suffer from problems of poor ohmic contact at the back electrode. Thus similar strategies are applied to minimize this problem. Despite the challenges faced by flexible structures, efficiencies of up to 13.8% and 7.8% have been achieved in superstrate and substrate cell, respectively. Based on these analyses, new strategies have been proposed for obtaining cheaper, more efficient, and viable flexible CdTe solar cells of the future.

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Section: Superstrate and Substrate Structures In Thin Film Solar Cellsmentioning

confidence: 99%

Section: Superstrate and Substrate Structures In Thin Film Solar Cellsmentioning

confidence: 99%

Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

Aliyu

Islam

Hamzah

et al. 2012

International Journal of Photoenergy

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“…In a separate study, Sb2Te3 was also found to be chemically stable when it was used at the back contact of CdTe solar cells [7,8]. However, other groups [9,10] have reported difficulties in obtaining high efficiency devices with Sb2Te3 as a back contact material in either superstrate or substrate configuration. In this study we report on the growth morphology and charge transport properties of sputtered Sb2Te3 films and also their suitability as back contacts to sputtered CdTe solar cells.…”

Section: Introductionmentioning

confidence: 98%

Studies of rf sputtered Sb<inf>2</inf>Te<inf>3</inf> thin films for back contacts to CdS/CdTe solar cells

Paudel

Wieland

Nawarange

et al. 2011

2011 37th IEEE Photovoltaic Specialists Conference

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Sb2Te3 films were magnetron sputtered using a 99.999% pure Sb2Te3 target from Cerac to study their growth morphology and transport properties. Optical emission spectroscopy was used to monitor the plasma conditions during growth. The films were grown on aluminosilicate glass substrates at temperatures from ~30 o C to 270 o C and characterized by x-ray diffraction, four point probe, and Hall-effect studies. All the films had a metallic luster, were opaque in the visible, and increased in grain size as substrate temperature increased. The best films were obtained when the sputtering was done at 240 o C substrate temperature. The grain size reached 80 nm, hole carrier concentration 2 x 10 20 cm -3 , mobility 146 cm 2 /V-s and the resistivity 4.1 : Pm. Based on these results, two-micron-thick sputtered CdS/CdTe solar cells were completed with Sb2Te3 as part of the back contact and yielded efficiency >12%, with open-circuit voltage ~780 mV, fill-factor ~72% and short-circuit current ~22 mA/cm 2 when 3 nm Cu and 20 nm Au was evaporated on top of the Sb2Te3 layer. Cells finished with Sb2Te3/Mo back contacts (without copper) yielded up to 10% efficiency. The lower efficiency when Cu is not used suggests that the Cu is still needed to modify the CdTe/Sb2Te3 interface when Sb2Te3 is used.

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“…The CdCl2 treatment is necessary to produce high performing devices due to the beneficial structural and electrical impact on CdS/CdTe heterojunction devices. However, a weak CdCl2 activation treatment results in poorly passivated grains, limiting the performance of the device, whilst an aggressive CdCl2 activation process can cause excessive consumption of the CdS layer and may damage the junction with excessive chlorine build up at the interface [2], leading to delamination [3]. Usually optimization of this process consists of assessing the performance of completed devices which can be very time consuming and not cost effective.…”

Section: Introductionmentioning

confidence: 99%

Photoluminescence imaging analysis of doping in thin film CdS and CdS/CdTe devices

Potamialis

Lisco

Maniscalco

et al. 2017

2017 IEEE 44th Photovoltaic Specialist Conference (PVSC)

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The use of photoluminescence (PL) imaging analysis to assess the effectiveness of the passivation treatment due to the presence of chlorine in CdS thin films has been investigated. In this work, we show that the chlorine doping effect in the CdS window layer can be detected by PL imaging analysis, due to the formation of a defect complex of sulfur vacancy and ClS (VS-ClS) and complexes between halogen ions and cadmium vacancies (VCd-ClS). CdTe devices with differently doped CdS layers were investigated. PL imaging, TEM, IV performance indicators and EQE analysis were performed to understand the effect of the different dopants on the electrical performances of CdTe devices.

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Development of back contacts for CdTe thin film solar cells deposited on flexible foil substrates

Cited by 9 publications

References 11 publications

Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

Recent Developments of Flexible CdTe Solar Cells on Metallic Substrates: Issues and Prospects

Studies of rf sputtered Sb<inf>2</inf>Te<inf>3</inf> thin films for back contacts to CdS/CdTe solar cells

Photoluminescence imaging analysis of doping in thin film CdS and CdS/CdTe devices

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