Highly conductive ZnO films with high near infrared transparency

Hála, Matěj; Fujii, Shohei; Redinger, Alex; Inoue, Yuriko; Rey, Germain; Thevenin, Maxime; Deprédurand, Valérie; Weiss, Thomas Paul; Bertram, Tobias; Siebentritt, Susanne

doi:10.1002/pip.2601

Cited by 22 publications

(18 citation statements)

References 46 publications

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“…1(a) it can be seen that an occasional drop in b-ZnO film resistivity that further lowers the corresponding ∆ρ is observed. The reason for this unexpected behaviour is not yet understood, as the previously assumed correlation with the season of the year [1] was not confirmed. However, one can speculate that the actual air humidity during the resistivity analyses may be of importance since the drop in ∆ρ is higher for thinner or more degraded samples that can exhibit a rougher surface; this effect is also witnessed by the pronounced drop in ρ of the ZnO 520 nm film after 22 months of anneling, as visible in Fig.…”

Section: A Ambient Air Ageingmentioning

confidence: 82%

“…In consequence, their transparency in near infrared (NIR) spectral region is significantly improved. Furthermore, a replacement of AZO by b-ZnO as an n-doped window of various chalcopyrite and kesterites thin film solar cells was shown to enhance short-circuit current [1].…”

Section: Introductionmentioning

confidence: 99%

“…In our recent work [1] we reported on preparation and characteristics of highly conductive ZnO layers (ρ ≤ 1 · 10 −3 Ω cm) prepared from nominally undoped ZnO target under the condition of a low-power radio frequency (RF) substrate biasing. These layers, labelled as b-ZnO films, exhibit 2.5 times lower charge carrier density in comparison to commonly-employed ZnO:Al (AZO) films of identical resistivity.…”

Section: Introductionmentioning

confidence: 99%

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Environmental stability of highly conductive nominally undoped ZnO layers

Hála

Inoue

Kato

et al. 2016

2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)

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Abstract-Highly conductive nominally undoped ZnO (b-ZnO) films represent an attractive alternative for ZnO:Al windows employed in thin film solar cells. In order to assess their suitability for the PV industry, we examine here their stability in various environments. We show that the b-ZnO films can exhibit comparable stability to ZnO:Al films in both ambient and heated air. However, b-ZnO films degrade faster in accelerated open damp heat (DH) conditions, which can be related to their columnar microstructure. Finally, a b-ZnO multilayer coating with an improved environmental stability is presented.

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Section: A Ambient Air Ageingmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Environmental stability of highly conductive nominally undoped ZnO layers

Hála

Inoue

Kato

et al. 2016

2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)

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“…The biased zinc oxide is a highly conductive nominally undoped ZnO, obtained by means of an additional plasma near the substrate during sputter deposition and is characterized by its high infrared transparency, which makes it particularly useful for low bandgap cells. Details can be found in . Magnesium fluoride (MgF 2 ) antireflection coating (ARC) layer was deposited at the top of the 3 cells using the same electron beam deposition tool.…”

Section: Methodsmentioning

confidence: 99%

High‐performance low bandgap thin film solar cells for tandem applications

Elanzeery

Babbe

Melchiorre

et al. 2018

Progress in Photovoltaics

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Thin film tandem solar cells provide a promising approach to achieve high efficiencies. | INTRODUCTIONCurrently, there is an increasing demand to provide cheap high-efficiency solar cells that can exceed state-of-the-art single-junction solar cell technologies. One approach to achieve this is through using tandem solar cells. Tandem or multijunction solar cells have the potential to achieve efficiencies of more than 30%. set the full illumination intensity for the IVT measurements. A mechanical shutter was used to allow dark and illuminated measurements within the same experiment. Admittance measurements were performed in the dark, after keeping the sample mounted in the dark at room temperature for 1 night, with an LCR meter using the same cryostat setup. All characterizations were performed after adding the ARC layer. For the extraction of the quasi-Fermi-level splitting (qFLS), photoluminescence (PL) spectra were recorded on CdS-covered absorbers in a home-built calibrated setup at room temperature under continuous monochromatic illumination with 660-nm wavelength. 27,28The spectral and absolute corrected PL spectra are converted into energy space. In a semilogarithmic plot, the high-energy wing of the PL peak is fitted linearly and is evaluated by means of the simplified Planck's generalized law, 29 providing the qFLS as well as the temperature. Figure 1A. Figure 1 A also presents the electrical behavior under light for CIS_0.95 measured in-house. Table 1 as a function of absorber bandgap are shown in Figure 2. All IV measurements were performed after adding an ARC layer.In Figure 1A, it is observed that V OC increases and J summarized in Table 1, it can be concluded that the cells lose more in recombination than in incomplete absorption (η el < η op ). Moreover, the

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“…Such analysis assumes a relation between the optical absorption coefficient (α) and the photon energy which is α 2 ∝ ( E–E g ) for direct band gap and α ∝ ( E–E g ) 2 for indirect band gap materials . The parameter α is calculated from film thickness, t , transmittance, T , and reflectance, R , by

α = - (\frac{1}{t}) \ln (\frac{T}{1 - R}) .

…”

Section: Resultsmentioning

confidence: 99%

Tuning the Optoelectronic Properties of ZnO:Al by Addition of Silica for Light Trapping in High‐Efficiency Crystalline Si Solar Cells

Dabirian

Nicolás

Niesen

et al. 2015

Adv Materials Inter

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by ultrathin intrinsic hydrogenated amorphous Si (a-Si:H) layers thus enabling open-circuit voltages as high as 750 mV. [ 2 ] The Ohmic losses between doped a-Si:H layers and metallic electrodes of the SHJ device are minimized by inserting a TCO layer in between. These TCO layers provide additional functionalities of antirefl ection in front of the cell [ 3 ] and the possibility of infrared (IR) light management in the cell rear-contact. [7][8][9] Optical absorption in the IR induced by free carriers in TCOs can signifi cantly deteriorate the generated photocurrent of the PV device. [ 10 ] These losses can be minimized by making the TCO more transparent often by reducing oxygen vacancies. However, this approach results in an increase of TCO refractive index, which is undesirable when the TCO is located at the rear of the device and covered by a metal layer. In such a case, the high refractive index of the TCO yields more efficient coupling to the surface plasmon polariton (SPP) modes of the metallic rear-contact, resulting in parasitic optical absorption losses. [7][8][9] Therefore, strategies that simultaneously reduce the refractive index and the IR absorption loss of TCOs are appealing in IR light management of c-Si solar cells, as well as in all devices incorporating a TCO/metal stack.In this article, we propose the addition of SiO 2 to ZnO:Al as a strategy to synthesize highly transparent TCOs with a low refractive index. We evaluate the performance of these TCOs for IR light management in SHJ solar cells to minimize optical absorption losses in the TCO and the metallic rear-contact. We should mention that Si doping of ZnO-based TCOs has been studied in the context of thin fi lm transistors (TFT) to either stabilize the TFT [ 11,12 ] or to improve the conductivity of the TCO. [ 13 ] Such studies have been primarily focused on a few percent concentrations of Si in ZnO where Si functions as an impurity doping. Our work addresses the refractive index tuning of ZnO:Al by SiO 2 addition in a range of concentrations wide enough to observe both electronic and structural modifi cations of ZnO:Al layers by addition of SiO 2 . We synthesize ZnO:Al with different concentration of SiO 2 up to 52 mol% SiO 2 in a cosputtering process. We analyze the chemical and structural properties of the obtained compounds and classify whether SiO 2 affects the electronic or structural properties of the ZnO:Al Highly transparent electrodes with a well-tuned refractive index are essential for a wide range of optoelectronic devices, such as light emitting diodes and solar cells. Here, it is shown that the transparency of ZnO:Al can be improved and its refractive index can be reduced simultaneously by the addition of SiO 2 into the layer. It is found that for low SiO 2 concentrations, Si quenches oxygen vacancies and improves the layer transparency. At higher SiO 2 concentrations a highly transparent amorphous compound of Zn x Si y O:Al forms, with a refractive index that scales down with the relative Si/Zn ratio. These layers are tes...

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Highly conductive ZnO films with high near infrared transparency

Cited by 22 publications

References 46 publications

Environmental stability of highly conductive nominally undoped ZnO layers

Environmental stability of highly conductive nominally undoped ZnO layers

High‐performance low bandgap thin film solar cells for tandem applications

Tuning the Optoelectronic Properties of ZnO:Al by Addition of Silica for Light Trapping in High‐Efficiency Crystalline Si Solar Cells

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