ORCID Profile
0000-0002-6363-4591
Current Organisation
Helmholtz-Zentrum Berlin für Materialien und Energie
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Publisher: Elsevier BV
Date: 08-2015
Publisher: Wiley
Date: 04-2007
Publisher: Wiley
Date: 21-11-2021
Abstract: A quantitative analysis of the thermally induced degradation of various device‐relevant multi‐cation hybrid perovskite films is performed using spectroscopic ellipsometry, for temperatures between 80 and 120 °C. The studied compositions are a triple cation perovskite Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(Br 0.17 I 0.83 ) 3 , a Rb‐containing variant Rb 0.05 Cs 0.05 (MA 0.17 FA 0.83 ) 0.90 Pb(Br 0.17 I 0.83 ) 3 , and a methylammonium‐free Rb 0.05 Cs 0.10 FA 0.85 PbI 3 composition. A very wide combined spectral range of 200 nm to 25 μm is covered by combining the data from two separate instruments. The relative changes in organic cation concentrations are quantified from the middle infrared molecular absorption bands, leveraging the use of point‐by‐point fitting for increased sensitivity. Additionally, the formation of PbI 2 and non‐perovskite δ‐CsPbI 3 phases is evidenced from Bruggemann effective medium fits to the visible and ultraviolet complex refractive indices. Methylammonium is almost completely depleted from the relevant compositions within 100 to 285 min of thermal annealing. The MA‐free perovskite degrades faster at intermediate temperatures, which is attributed to phase instability due to the formation of δ‐CsPbI 3 in addition to PbI 2 .
Publisher: Elsevier BV
Date: 04-2006
Publisher: Elsevier BV
Date: 06-2009
Publisher: Elsevier BV
Date: 03-2010
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 10-2005
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2021
Publisher: Elsevier BV
Date: 03-2014
Publisher: SPIE
Date: 10-02-2011
DOI: 10.1117/12.874967
Publisher: Elsevier BV
Date: 12-2011
Publisher: Wiley
Date: 06-05-2009
Publisher: Elsevier BV
Date: 12-2009
Publisher: Elsevier BV
Date: 05-2004
Publisher: Elsevier BV
Date: 10-2013
Publisher: Wiley
Date: 29-05-2020
DOI: 10.1111/RAQ.12426
Publisher: Wiley
Date: 04-2007
Publisher: AIP Publishing
Date: 10-06-2002
DOI: 10.1063/1.1485117
Abstract: The perturbed angular correlation method was employed to study the lattice environment of In implanted into GaN. It was found, after annealing the implantation induced damage, that 65% of the implanted atoms were situated in regular undisturbed Ga lattice sites. The remaining fraction showed an unusual behavior insofar as its lattice surroundings changed reversibly from undisturbed at temperatures above 600 K to strongly disturbed at low temperatures.
Publisher: SPIE
Date: 15-05-2014
DOI: 10.1117/12.2052167
Publisher: Elsevier BV
Date: 04-2012
Publisher: SPIE
Date: 15-05-2014
DOI: 10.1117/12.2052362
Publisher: AIP Publishing
Date: 15-10-2009
DOI: 10.1063/1.3240343
Abstract: Polycrystalline silicon (poly-Si) thin films have been prepared by electron-beam evaporation and thermal annealing for the development of thin-film solar cells on glass coated with ZnO:Al as a transparent, conductive layer. The poly-Si microstructure and photovoltaic performance were investigated as functions of the deposition temperature by Raman spectroscopy, scanning and transmission electron microscopies including defect analysis, x-ray diffraction, external quantum efficiency, and open circuit measurements. It is found that two temperature regimes can be distinguished: Poly-Si films fabricated by deposition at low temperatures (Tdep& °C) and a subsequent thermal solid phase crystallization step exhibit 1–3 μm large, randomly oriented grains, but a quite poor photovoltaic performance. However, silicon films deposited at higher temperatures (Tdep& °C) directly in crystalline phase reveal columnar, up to 300 nm big crystals with a strong ⟨110⟩ orientation and much better solar cell parameters. It can be concluded from the results that the electrical quality of the material, reflected by the open circuit voltage of the solar cell, only marginally depends on crystal size and shape but rather on the intragrain properties of the material. The carrier collection, described by the short circuit current of the cell, seems to be positively influenced by preferential ⟨110⟩ orientation of the grains. The correlation between experimental, microstructural, and photovoltaic parameters will be discussed in detail.
Publisher: AIP Publishing
Date: 10-10-2011
DOI: 10.1063/1.3644084
Abstract: The chemical structure of the interface between silicon thin films and the transparent conductive oxide ZnO:Al has been investigated by hard x-ray photoelectron spectroscopy. By varying the excitation energy between 2010 and 8040 eV, we were able to probe the Si/ZnO interface buried below 12 nm Si. This allowed for the identification of changes induced by solid phase crystallization (SPC). Based on in-situ SPC annealing experiments, we find clear indications that the formation of Si–O bonds takes place at the expense of Zn–O bonds. Hence, the ZnO:Al acts as the oxygen source for the interfacial Si oxidation.
Publisher: Elsevier BV
Date: 03-2014
Publisher: Elsevier BV
Date: 07-2011
Publisher: AIP Publishing
Date: 04-11-2013
DOI: 10.1063/1.4829999
Publisher: Elsevier BV
Date: 11-2015
Publisher: Elsevier BV
Date: 09-2014
Publisher: Elsevier BV
Date: 07-2008
Publisher: Elsevier BV
Date: 09-2015
Publisher: IOP Publishing
Date: 23-04-2012
Publisher: Wiley
Date: 21-05-2013
DOI: 10.1002/PIP.2389
Publisher: SPIE
Date: 09-02-2012
DOI: 10.1117/12.908969
Publisher: Wiley
Date: 27-11-2014
Publisher: Wiley
Date: 25-10-2013
Publisher: Elsevier BV
Date: 09-2014
Publisher: AIP Publishing
Date: 10-12-2007
DOI: 10.1063/1.2824456
Abstract: The crystallization of thin silicon films at temperatures between 425 and 600°C was investigated on glass substrates coated with Al-doped zinc oxide (ZnO:Al). Bare ZnO:Al layers degrade at the crystallization temperatures used. A silicon layer on top, however, efficiently prevents deterioration. The resistivity was even found to drop from 4.3×10−4Ωcm for the as deposited ZnO:Al to 2.2×10−4Ωcm in the case of aluminium induced crystallization and to 3.4×10−4Ωcm for solid phase crystallization. The temperature-stable conductivity of ZnO:Al films coated with Si opens up appealing options for the production of polycrystalline silicon thin-film solar cells with transparent front contacts.
Publisher: Elsevier BV
Date: 04-2012
Publisher: Elsevier BV
Date: 02-2006
Publisher: AIP Publishing
Date: 16-08-2010
DOI: 10.1063/1.3462316
Abstract: The chemical interface structure between phosphorus-doped hydrogenated amorphous silicon and aluminum-doped zinc oxide thin films is investigated with soft x-ray emission spectroscopy (XES) before and after solid-phase crystallization (SPC) at 600 °C. In addition to the expected SPC-induced phase transition from amorphous to polycrystalline silicon, our XES data indicates a pronounced chemical interaction at the buried Si/ZnO interface. In particular, we find an SPC-enhanced formation of Si–O bonds and the accumulation of Zn in close proximity to the interface. For an assumed closed and homogeneous SiO2 interlayer, an effective thickness of (5±2) nm after SPC could be estimated.
Publisher: American Physical Society (APS)
Date: 21-04-2011
Publisher: SPIE
Date: 18-03-2013
DOI: 10.1117/12.2001290
Publisher: Elsevier BV
Date: 04-2014
Publisher: Wiley
Date: 28-08-2013
Publisher: IOP Publishing
Date: 04-2023
Abstract: We present monolithic copper–indium–gallium–diselenide (Cu(In,Ga)Se 2 , CIGSe)-perovskite tandem solar cells with air- or N 2 -transferred NiO x :Cu with or without self-assembled monolayer (SAM) as a hole-transporting layer (HTL). A ch ion efficiency of 23.2%, open-circuit voltage (V o c ) of 1.69 V, and a fill factor (FF) of 78.3% are achieved for the tandem with N 2 -transferred NiO x :Cu + SAM. The s les with air-transferred NiO x :Cu + SAM have V o c and FF losses, while those without SAM are heavily shunted. We find via x-ray and UV photoelectron spectroscopy that the air exposure leads to non-negligible loss in the Ni 2+ species and changes in the NiO x :Cu’s work function and valence band maxima, both of which can negatively impact the V o c and the FF of the tandems. Furthermore, by performing dark lock-in thermography, photoluminescence (PL), and scanning electron microscopy studies, we are able to detect various morphological defects in the tandems with poor performance, such as ohmic shunts originating from defects in the bottom CIGSe cell, or from cracking/delaminating of the perovskite top cell. Finally, by correlating the detected shunts in the tandems with PL-probed bottom device, we can conclude that not all defects in the bottom device induce ohmic shunts in the tandems since the NiO x :Cu + SAM HTL bi-layer can decouple the growth of the top device from the rough, defect-rich and defect-tolerant bottom device and enable high-performing devices.
Publisher: Elsevier BV
Date: 02-2009
Publisher: SPIE
Date: 08-03-2014
DOI: 10.1117/12.2039278
Publisher: Elsevier BV
Date: 05-2008
Publisher: Elsevier BV
Date: 12-2009
Publisher: Wiley
Date: 26-05-2014
Abstract: In order to clarify the origin of the previously reported reduction of sub‐band gap absorption of sputtered ZnO:Al films upon thermal annealing and raising deposition temperature, structural characterization using Ra‐man spectroscopy was carried out on various films. Correlation of the Urbach energy to the FWHM of the E (high) 2 mode was found. Oxygen addition to the film growth did not result in changes of the Urbach energy, despite pronounced changes of the electrical properties. The results suggest that extended defects, rather than intrinsic point defects, give rise to the sub‐band gap absorption. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Publisher: AIP Publishing
Date: 2010
DOI: 10.1063/1.3269721
Abstract: A postdeposition thermal treatment has been applied to sputtered Al-doped zinc oxide films and shown to strongly decrease the resistivity of the films. While high temperature annealing usually leads to deterioration of electrical transport properties, a silicon capping layer successfully prevented the degradation of carrier concentration during the annealing step. The effect of annealing time and temperature has been studied in detail. A mobility increase from values of around 40 cm2/Vs up to 67 cm2/Vs, resulting in a resistivity of 1.4×10−4 Ω cm has been obtained for annealing at temperatures of 650 °C. The high mobility increase is most likely obtained by reduced grain boundary scattering. Changes in carrier concentration in the films caused by the thermal treatment are the result of two competing processes. For short annealing procedures we observed an increase in carrier concentration that we attribute to hydrogen diffusing into the zinc oxide film from a silicon nitride barrier layer between the zinc oxide and the glass substrate and the silicon capping layer on top of the zinc oxide. Both are hydrogen-rich if deposited by plasma-enhanced chemical vapor deposition. For longer annealing times a decrease in carrier concentration can occur if a thin capping layer is used. This can be explained by the deteriorating effect of oxygen during thermal treatments which is well known from annealing of uncapped zinc oxide films. The reduction in carrier concentration can be prevented by the use of capping layers with thicknesses of 40 nm or more.
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 06-2009
Publisher: Royal Society of Chemistry (RSC)
Date: 28-10-2014
DOI: 10.1039/C4CP03364G
Abstract: The interface between solid-phase crystallized phosphorous-doped polycrystalline silicon (poly-Si(n(+))) and aluminum-doped zinc oxide (ZnO:Al) was investigated using spatially resolved photoelectron emission microscopy. We find the accumulation of aluminum in the proximity of the interface. Based on a detailed photoemission line analysis, we also suggest the formation of an interface species. Silicon suboxide and/or dehydrated hemimorphite have been identified as likely candidates. For each scenario a detailed chemical reaction pathway is suggested. The chemical instability of the poly-Si(n(+))/ZnO:Al interface is explained by the fact that SiO2 is more stable than ZnO and/or that H2 is released from the initially deposited a-Si:H during the crystallization process. As a result, Zn (a deep acceptor in silicon) is "liberated" close to the silicon/zinc oxide interface presenting the inherent risk of forming deep defects in the silicon absorber. These could act as recombination centers and thus limit the performance of silicon/zinc oxide based solar cells. Based on this insight some recommendations with respect to solar cell design, material selection, and process parameters are given for further knowledge-based thin-film silicon device optimization.
Publisher: Elsevier BV
Date: 12-2012
Publisher: Elsevier BV
Date: 10-2007
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2020
Location: Germany
Location: Germany
Location: Germany
No related grants have been discovered for Florian Ruske.