Atomic layer deposited zinc oxysulfide n-type buffer layers for Cu2ZnSn(S,Se)4 thin film solar cells

Hong, Hee Kyeung; Kim, In Young; Shin, Seung Wook; Song, Gwang Yeom; Cho, Jae Yu; Gang, Myeng Gil; Shin, Jae Cheol; Kim, Jihun; Heo, Jaeyeong

doi:10.1016/j.solmat.2016.04.054

Cited by 28 publications

(32 citation statements)

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“…A few ternary materials have shown potential as alternative buffer candidate material for kesterite-based TFSCs. They have the advantage of having (optoelectronic) properties that can easily be tuned by controlling their stoichiometry [156][157][158][159][160][161]. For Zn(O, S) buffer layers prepared by ALD, e.g.…”

Section: Zns-based Buffer Layersmentioning

confidence: 99%

“…the S/O ratio can easily be varied. However, kesterite devices with ALD Zn(O, S) buffer layers have not yet shown high PCEs [156,159,160]. Recently, Zhang et al [157] fabricated CZTS-based TFSCs with ozone assisted photochemical deposited Zn(O, S) buffer layers having a band gap ranging between 3.3-3.7 eV, tuned by a variable ozone flow rate.…”

Section: Zns-based Buffer Layersmentioning

confidence: 99%

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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: Zns-based Buffer Layersmentioning

confidence: 99%

Section: Zns-based Buffer Layersmentioning

confidence: 99%

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

et al. 2019

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“…On the other hand, when more S was incorporated in the ZnO film, the crystalline phase again appeared which exhibited a high‐intensity XRD peak at a slightly higher angle than pure ZnS as observed for the ZnOS‐1:2 film. Thus, this study clearly revealed the structural change of as‐grown ZnOS films from O‐rich to S‐rich phases through the crystalline‐amorphous‐crystalline phase transitions ( Figure ) …”

Section: Resultsmentioning

confidence: 53%

Revealing the Simultaneous Effects of Conductivity and Amorphous Nature of Atomic‐Layer‐Deposited Double‐Anion‐Based Zinc Oxysulfide as Superior Anodes in Na‐Ion Batteries

Sinha

Didwal

Nandi

et al. 2019

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Although sodium‐ion batteries (SIBs) are considered promising alternatives to their Li counterparts, they still suffer from challenges like slow kinetics of the sodiation process, large volume change, and inferior cycling stability. On the other hand, the presence of additional reversible conversion reactions makes the metal compounds the preferred anode materials over carbon. However, conductivity and crystallinity of such materials often play the pivotal role in this regard. To address these issues, atomic layer deposited double‐anion‐based ternary zinc oxysulfide (ZnOS) thin films as an anode material in SIBs are reported. Electrochemical studies are carried out with different O/(O+S) ratios, including O‐rich and S‐rich crystalline ZnOS along with the amorphous phase. Amorphous ZnOS with the O/(O+S) ratio of ≈0.4 delivers the most stable and considerably high specific (and volumetric) capacities of 271.9 (≈1315.6 mAh cm−3) and 173.1 mAh g−1 (≈837.7 mAh cm−3) at the current densities of 500 and 1000 mA g−1, respectively. A dominant capacitive‐controlled contribution of the amorphous ZnOS anode indicates faster electrochemical reaction kinetics. An electrochemical reaction mechanism is also proposed via X‐ray photoelectron spectroscopy analyses. A comparison of the cycling stability further establishes the advantage of this double‐anion‐based material over pristine ZnO and ZnS anodes.

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Section: Resultsmentioning

confidence: 95%

“…The results above demonstrate that it is possible to control the characteristics of Zn(O,S) thin-films by adjusting their composition. Additionally, the results indicate the potential to develop an optimal band structure between the CIGSSe absorber layer and the Zn(O,S) buffer layer using the variation in bandgap energy, depending on the composition [11][12][13]. The application of the ALD method in the deposition of a Zn(O,S) thin-film reduces the occurrence of defects inside the film because the film is formed monolayer by monolayer, and thus, electrons generated by the photovoltaic reaction are less likely to be trapped (or captured) when passing through the buffer layers.…”

Section: Resultsmentioning

confidence: 96%

The Effect of ALD-Zn(O,S) Buffer Layer on the Performance of CIGSSe Thin Film Solar Cells

Choi

Park²,

Kim

et al. 2020

Energies

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In this paper, we report the development of Cd-free buffers using atomic layer deposition (ALD) for Cu(In,Ga)(S,Se)2-based solar cells. The ALD process gives good control of thickness and the S/S +O ratio content of the films. The influence of the growth per cycle (GPC) and the S/(S+O) ratio, and the glass temperature of the atomic layer deposited Zn(O,S) buffer layers on the efficiency of the Cu(In,Ga)(S,Se)2 solar cells were investigated. We present the first results from our work on cadmium-free CIGS solar cells on substrates with an aperture area of 0.4 cm2. These Zn(O,S) layers were deposited by atomic layer deposition at 120 °C with S/Zn ratios of 0.7, and layers of around 30 nm. The Zn(O,S) 20% (Pulse Ratio: H2S/H2O+H2S) process results in a S/Zn ratio of 0.7. We achieved independently certified aperture area efficiencies of 17.1% for 0.4 cm2 cells.

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Atomic layer deposited zinc oxysulfide n-type buffer layers for Cu2ZnSn(S,Se)4 thin film solar cells

Cited by 28 publications

References 50 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

Revealing the Simultaneous Effects of Conductivity and Amorphous Nature of Atomic‐Layer‐Deposited Double‐Anion‐Based Zinc Oxysulfide as Superior Anodes in Na‐Ion Batteries

The Effect of ALD-Zn(O,S) Buffer Layer on the Performance of CIGSSe Thin Film Solar Cells

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