Influence of Amorphous Silicon Carbide Intermediate Layer in the Back-Contact Structure of Cu<sub>2</sub>ZnSnSe<sub>4</sub>Solar Cells

Colina, M.; Martı́n, I.; Giraldo, Sergio; Sánchez, Yudania; Kondrotas, Rokas; Oliva, Florian; Izquierdo-Roca, Víctor; Pérez-Rodrı́guez, A.; Coll, Arnau; Alcubilla, R.; Saucedo, Edgardo

doi:10.1109/jphotov.2016.2591328

Cited by 8 publications

(3 citation statements)

References 32 publications

(19 reference statements)

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“…As reviewed recently by Englund et al, interlayers of pure metals as well as various metal borides, carbides, nitrides, and oxides have been deposited between the Mo and CZTS(e) layers for this purpose [49]. In two cases (TiN [16,50]) the final device efficiency was not improved, but generally an improvement was obtained (TiN [51], Bi [52], Ag [53], C [54], TiB 2 [55], ZnO [56][57][58], a-SiC [59] , MoO x [23,60]). The reported improvements, however, did not result in devices with PCEs higher than 10%, suggesting that to date the Mo/Mo(S, Se) 2 layer stack is still the best back contact for CZTSSe solar cells.…”

Section: Protective Interlayers At the Back Contactmentioning

confidence: 99%

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

et al. 2019

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We review the present state-of-the-art within back and front contacts in kesterite thin film solar cells, as well as the current challenges. At the back contact, molybdenum (Mo) is generally used, and thick Mo(S, Se) 2 films of up to several hundred nanometers are seen in record devices, in particular for selenium-rich kesterite. The electrical properties of Mo(S, Se) 2 can vary strongly depending on orientation and indiffusion of elements from the device stack, and there are indications that the back contact properties are less ideal in the sulfide as compared to the selenide case. However, the electronic interface structure of this contact is generally not well-studied and thus poorly understood, and more measurements are needed for a conclusive statement. Transparent back contacts is a relatively new topic attracting attention as crucial component in bifacial and multijunction solar cells. Front illuminated efficiencies of up to 6% have so far been achieved by adding interlayers that are not always fully transparent. For the front contact, a favorable energy level alignment at the kesterite/CdS interface can be confirmed for kesterite absorbers with an intermediate [S]/([S]+[Se]) composition. This agrees with the fact that kesterite absorbers of this composition reach highest efficiencies when CdS buffer layers are employed, while alternative buffer materials with larger band gap, such as Cd 1−x Zn x S or Zn 1−x Sn x O y , result in higher efficiencies than devices with CdS buffers when sulfurrich kesterite absorbers are used. Etching of the kesterite absorber surface, and annealing in air or inert atmosphere before or after buffer layer deposition, has shown strong impact on device performance. Heterojunction annealing to promote interdiffusion was used for the highest performing sulfide kesterite device and air-annealing was reported important for selenium-rich record solar cells. Cu 2 ZnSnS 4 (CZTS) absorbers for solar cell applications was first reported by Ito and Nakazawa [1]. Early results on CZTS device performance were reported by Friedlmeier et al [2], Seol et al [3], and Katagiri et al [4]. Later a group at IBM reached record performances with power conversion efficiencies (PCEs) above 10% for CZTSSe devices in 2010 [5] and the current record PCE of 12.6% in 2013 [6]. In 2018, researchers from DGIST reached the same performance, 12.6%, but for a larger device area [7]. The device structure used for kesterite solar cells was originally copied from that of Cu(In, Ga)Se 2 , (CIGSe) TFSCs, and is formed by sequential deposition, upon a soda lime glass substrate, of a Mo back contact, the absorber, a CdS buffer layer, and a ZnO/ZnO:Al bi-layer window (i.e. transparent top contact). This structure, schematically shown for CZTSSe in figure 1, is not necessarily ideal for kesterite solar cells, and extensive work has been invested into studies of alternative backand front contacts and related deposition processes. In this paper, the state-of-the-art and current open questions related to the back and front c...

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Section: Protective Interlayers At the Back Contactmentioning

confidence: 99%

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

et al. 2019

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“…To optimize the design of the back contact, several successful strategies have been successfully implemented to reduce the series resistance and increase the fill factor including Ag with good conductivity and additional p-type doping, 11 ZnO, 12,13 MoO 2 14 with good chemical stability; TiN 8,15,16 and TiB 2 9 with both good chemical stability and electrical conductivity. More recently, bilayer structures SiC/Mo 17 and Au/MoO 3 18 were reported to mainly boost the open circuit voltage and hence improve the power conversion efficiency. Si x N y is a dielectric material with excellent chemical and thermal stability 19 and has been used as an antireflection coating (ARC), as well as a moisture barrier for crystalline silicon 20 and CIGS solar cells.…”

Section: ■ Introductionmentioning

confidence: 99%

Engineering of a Mo/Si_xN_y Diffusion Barrier to Reduce the Formation of MoS₂ in Cu₂ZnSnS₄ Thin Film Solar Cells

Wei

Fung

Pockett

et al. 2018

ACS Appl. Energy Mater.

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The optimisation of the interface between back contact and absorber is one of the main challenges to improve the electrical behaviour and further enhance the efficiencies of Cu 2 ZnSn(S,Se) 4 (CZTS(e)) solar cell devices. In this work, Mo/Si x N y thin films with various film thicknesses were introduced as an interfacial layer to explore its influence on opto-electronic properties of the pure sulphide CZTS thin film solar cells. The Si x N y was deposited through plasma enhanced chemical vapour deposition (PECVD). The film thickness and stress of the Mo/Si x N y films were controlled to improve the adhesion of the CZTS layer and reduce the chances of cracking the deposited films. Energy dispersive X-Ray spectroscopy (EDS) mapping measurements performed directly on the cross-section of Mo/Si x N y /CZTS/Mo films indicate that the Si x N y intermediate layer can effectively inhibit the formation of a highly resistive MoS 2 layer and decomposition of CZTS at the CZTS/Molybdenum (Mo) interface region. A reduced efficiency was obtained with a Si x N y modified back contact compared with the devices without this layer. This could be due to the increased recombination and poor hole extraction stemming from the very low valance band maximum of Si x N y obtained from ultraviolet photoelectron spectroscopy (UPS) measurements. Temperature dependent current density-voltage (T-JV) and temperature dependent transient photovoltage (T-TPV) measurements were used to uncover insights into the internal recombination dynamics of the charge carriers.

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“…It has been suggested that the introduction of interlayers, to work as, e.g., chemical‐ and/or electrical passivation layer between the Mo BC and the absorber layer, could be a route to overcome these issues. Many materials have been investigated to date, e.g., ZnO, Ag, TiB 2 , Au, W, Pd, Pt, Ni, TiW, Cr, Ti, Al, C, Bi, Al 2 O 3 , MoO x , TiN, SnS, a‐SiC, MoN, and S x iN y . The BC must supply sufficient adhesion to the absorber to avoid delamination, especially during critical processing steps as annealing and etching, it is therefore beneficial if it is chemically inert.…”

Section: Introductionmentioning

confidence: 99%

TiN Interlayers with Varied Thickness in Cu₂ZnSnS(e)₄ Thin Film Solar Cells: Effect on Na Diffusion, Back Contact Stability, and Performance

Englund

Grini

Donzel‐Gargand

et al. 2018

Physica Status Solidi (a)

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In this study, interlayers with varied thickness of TiN between Cu 2 ZnSnS(e) 4 (CZTS(e)) absorbers and Mo on soda-lime glass substrates are investigated for CZTS(e) thin film solar cells. Na diffusion is analyzed using Secondary Ion Mass Spectrometry and it is found that the use of thick TiN interlayers facilitates Na diffusion into the absorbers. The CZTS(e)/TiN/Mo interfaces are scrutinized using Transmission Electron Microscopy (TEM) Electron Energy Loss Spectroscopy (EELS). It is found that diffusion of chalcogens present in the precursor occurs through openings, resulting from surface roughness in the Mo, in the otherwise chemically stable TiN interlayers, forming point contacts of MoS(e) 2 . It is further established that both chalcogens and Mo diffuse along the TiN interlayer grain boundaries. Solar cell performance for sulfur-annealed samples improved with increased thickness of TiN, and with a 200 nm TiN interlayer, the solar cell performance is comparable to a typical Mo reference. Pure TiN bulk contacts are investigated and shown to work, but the performance is still inferior to the TiN interlayer back contacts. The use of thick TiN interlayers offers a pathway to achieve high efficiency CZTS(e) solar cells on highly inert back contacts.

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Influence of Amorphous Silicon Carbide Intermediate Layer in the Back-Contact Structure of Cu₂ZnSnSe₄Solar Cells

Cited by 8 publications

References 32 publications

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

Engineering of a Mo/Si_xN_y Diffusion Barrier to Reduce the Formation of MoS₂ in Cu₂ZnSnS₄ Thin Film Solar Cells

TiN Interlayers with Varied Thickness in Cu₂ZnSnS(e)₄ Thin Film Solar Cells: Effect on Na Diffusion, Back Contact Stability, and Performance

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Influence of Amorphous Silicon Carbide Intermediate Layer in the Back-Contact Structure of Cu2ZnSnSe4Solar Cells

Cited by 8 publications

References 32 publications

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

Back and front contacts in kesterite solar cells: state-of-the-art and open questions

Engineering of a Mo/SixNy Diffusion Barrier to Reduce the Formation of MoS2 in Cu2ZnSnS4 Thin Film Solar Cells

TiN Interlayers with Varied Thickness in Cu2ZnSnS(e)4 Thin Film Solar Cells: Effect on Na Diffusion, Back Contact Stability, and Performance

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Influence of Amorphous Silicon Carbide Intermediate Layer in the Back-Contact Structure of Cu₂ZnSnSe₄Solar Cells

Engineering of a Mo/Si_xN_y Diffusion Barrier to Reduce the Formation of MoS₂ in Cu₂ZnSnS₄ Thin Film Solar Cells

TiN Interlayers with Varied Thickness in Cu₂ZnSnS(e)₄ Thin Film Solar Cells: Effect on Na Diffusion, Back Contact Stability, and Performance