Recent developments in inkjet printing have proven it a viable method for low-cost and large-area coating of oxide materials. The main drawback of this method is the common requirement of a post-deposition annealing (PDA) of the printed layers at relatively high temperatures (T > 200 degrees C). This sets a requirement for the substrate to have high glass transition temperature (T-g). To reduce the PDA temperature, deep-ultraviolet (DUV) annealing is proposed as an effective method. In this study, yttrium aluminum oxide (YAlOx) dielectrics are realized for application in flexible electronic devices via inkjet printing and DUV annealing at a temperature of 150 degrees C. The effect of the Y concentration on the electrical properties of the dielectrics is investigated. An increase in the Y incorporation is found to increase the dielectric constant and decrease the leakage current of the dielectrics. Flexible indium gallium zinc oxide (IGZO) thin-film transistors with 50 mu m channel widths and 7 mu m channel lengths employing printed YAlOx dielectrics are fabricated on polyimide substrates with a maximum processing temperature of 150 degrees C, yielding a maximum gate leakage current of 10(-13)A, a high I-ON/I-OFF ratio of 10(8), and a field effect mobility of 4.3 cm(2) V-1 s(-1).

Compositional grading has been widely exploited in highly efficient Cu(In,Ga)Se 2 , CdTe, GaAs, quantum dot solar cells, and this strategy has the potential to improve the performance of emerging perovskite solar cells. However, realizing and maintaining compositionally graded perovskite absorber from solution processing is challenging. Moreover, the operational stability of graded perovskite solar cells under long‐term heat/light soaking has not been demonstrated. In this study, a facile partial ion‐exchange approach is reported to achieve compositionally graded perovskite absorber layers. Incorporating compositional grading improves charge collection and suppresses interface recombination, enabling to fabricate near‐infrared‐transparent perovskite solar cells with power conversion efficiency of 16.8% in substrate configuration, and demonstrate 22.7% tandem efficiency with 3.3% absolute gain when mechanically stacked on a Cu(In,Ga)Se 2 bottom cell. Non‐encapsulated graded perovskite device retains over 93% of its initial efficiency after 1000 h operation at maximum power point at 60 °C under equivalent 1 sun illumination. The results open an avenue in exploring partial ion‐exchange to design graded perovskite solar cells with improved efficiency and stability.

This review summarizes the current status of Cu(In,Ga) (S,Se)(2) (CIGS) thin film solar cell technology with a focus on recent advancements and emerging concepts intended for higher efficiency and novel applications. The recent developments and trends of research in laboratories and industrial achievements communicated within the last years are reviewed, and the major developments linked to alkali post deposition treatment and composition grading in CIGS, surface passivation, buffer, and transparent contact layers are emphasized. Encouraging results have been achieved for CIGS-based tandem solar cells and for improvement in low light device performance. Challenges of technology transfer of lab's record high efficiency cells to average industrial production are obvious from the reported efficiency values. One section is dedicated to development and opportunities offered by flexible and lightweight CIGS modules. Copyright (C) 2016 John Wiley & Sons, Ltd.

Advanced Materials InterfacesVolume 4, Issue 1 1600289 Communication Bio-Inspired Superhydrophobic and Omniphobic Wood Surfaces Huizhang Guo, Corresponding Author Huizhang Guo [email protected] Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandE-mail: [email protected], [email protected]Search for more papers by this authorPeter Fuchs, Peter Fuchs Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorKirstin Casdorff, Kirstin Casdorff Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorBenjamin Michen, Benjamin Michen Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorMunish Chanana, Munish Chanana Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorHarald Hagendorfer, Harald Hagendorfer Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorYaroslav E. Romanyuk, Yaroslav E. Romanyuk Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorIngo Burgert, Corresponding Author Ingo Burgert [email protected] Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandE-mail: [email protected], [email protected]Search for more papers by this author Huizhang Guo, Corresponding Author Huizhang Guo [email protected] Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandE-mail: [email protected], [email protected]Search for more papers by this authorPeter Fuchs, Peter Fuchs Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorKirstin Casdorff, Kirstin Casdorff Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorBenjamin Michen, Benjamin Michen Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorMunish Chanana, Munish Chanana Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorHarald Hagendorfer, Harald Hagendorfer Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorYaroslav E. Romanyuk, Yaroslav E. Romanyuk Laboratory for Thin Films and Photovoltaics, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandSearch for more papers by this authorIngo Burgert, Corresponding Author Ingo Burgert [email protected] Wood Materials Science, Institut for Building Materials, ETH Zürich, Stefano-Franscini-Platz 3, 8093 Zürich, Switzerland Applied Wood Materials, Empa-Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandE-mail: [email protected], [email protected]Search for more papers by this author First published: 09 November 2016 https://doi.org/10.1002/admi.201600289Citations: 45Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Bio-inspired superhydrophobic and omniphobic wood surfaces that exhibit extremely low wettability for both, aqueous (blue drop) and non-aqueous (red drop) liquids, were obtained by adding a nano-scaled structure to the intrinsically micro-scaled texture of the wood surface. Citing Literature Supporting Information As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Filename Description admi201600289-sup-0001-S1.pdf1.5 MB Supplementary admi201600289-sup-0002-S2.avi3.8 MB Supplementary admi201600289-sup-0003-S3.avi5.4 MB Supplementary admi201600289-sup-0004-S4.avi2.9 MB Supplementary admi201600289-sup-0005-S5.avi2.1 MB Supplementary admi201600289-sup-0006-S6.avi3.1 MB Supplementary Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume4, Issue1Special Issue: Max-Planck Institute of Colloids and Interfaces Perspectives in Interface Research January 9, 20171600289 RelatedInformation

Transparent conductive zinc oxide thin films are deposited by chemical bath deposition (CBD) followed by exposure to UV‐visible light to increase their electrical conductivity. Selected spectral bandwidths are filtered from a Hg(Xe) lamp in the range of 280–546 nm to investigate resistivity transients as a function of the illumination wavelength. The conductivity increases by a factor of ∼103 for illumination wavelengths shorter than the fundamental absorption edge, as predicted by the ionized oxygen species adsorption model. If the thin film thickness exceeds the UV radiation penetration depth significantly (≳1 µm), the conductivity can most effectively be increased by exposing the films to wavelengths situated in the Urbach tail at ∼365 nm as both, absorptance and transmittance lie above 20%, enabling the radiation to penetrate the whole layer, while still locally generating enough electron‐hole pairs for the desorption of chemisorbed species.

This review summarizes the current status of Cu(In,Ga)(S,Se)2 (CIGS) thin film solar cell technology with a focus on recent advancements and emerging concepts intended for higher efficiency and novel applications. The recent developments and trends of research in labs and industrial achievements communicated within the last years are reviewed and the major developments linked to alkali post deposition treatment and composition grading in CIGS, surface passivation, buffer and transparent contact layers are emphasized. Encouraging results have been achieved for CIGS based tandem solar cells and for improvement in low light device performance. Challenges of technology transfer of lab’s record high efficiency cells to average industrial production are obvious from the reported efficiency values. One section is dedicated to development and opportunities offered by flexible and lightweight CIGS modules.

The development of a novel chemistry for the chemical bath deposition of Zn(O,S) buffer layers for Cu(In,Ga)Se2 (CIGS) solar cells is desired for a higher growth rate, hence reduced deposition time, while reducing simultaneously the required concentration of reactants. State-of-the-art recipes are based on thiourea as sulphide precursor requiring a high molarity of reactants and relatively long deposition times due to the slow decomposition rate of thiourea. In this contribution thioamide based sulphide precursors were investigated for their decomposition and growth behaviour. A co-solvent approach in an ethanolic/aqueous ammonia medium was evaluated omitting the need for additional complexants. By replacing thiourea with the investigated thioamides, homogeneous dense layers of around 30 nm were grown with a greatly decreased deposition time of 8 min compared to 25 min for thiourea. Likewise, the concentration of the sulphide precursor was 40-fold reduced. The photovoltaic performance as characterized by external quantum efficiency and current–voltage measurements, showed conversion efficiencies of 15% comparable to the thiourea based process.

Characterization of carbon adsorbates in solution-processed ZnO thin films exposed to UV light and humidity.

Inverted PTB7/PC71BM polymer solar cells are prepared on solution-processed Al:ZnO transparent contacts on PET substrates. Al:ZnO is deposited by a low temperature chemical bath deposition route (T < 100°C at any step) to comply with the temperature sensitive substrate. A maximum conversion efficiency of 6.4% and 6.9% is achieved for the indium-free solar cells on PET and glass substrates, respectively. The devices are relatively stable in air whereby an initial efficiency loss in the order of 15% after storage for 15 days can be fully recovered by light soaking.

One of the most significant limitations for a wider utilisation of the renewable and CO2-storing resource wood is its low ultraviolet (UV) light stability. The protection of the wood surface without altering its aesthetic appeal requires an optically transparent but UV protective coating which should be strongly attached to the rough and inhomogeneous substrate. For this purpose, ZnO nanostructures were deposited onto the wood surface via a chemical bath deposition process. The morphology of crystalline ZnO was controlled by aluminium nitrate or ammonium citrate in the growth step resulting in nanorod arrays or platelet structures, respectively. Detailed structural, chemical and mechanical characterisations as well as accelerated weathering exposure revealed the effective performance of the platelet structure, which formed a dense and thin ZnO coating on spruce. The total colour change (Delta E in the CIE system) was calculated to be 20.5 for unmodified wood, while it was about three for the modified samples after 4 weeks accelerated weathering test. Moreover, the ZnO coating also suppressed crack initiation and propagation indicating a substantial increase in durability.

The introduction of a KF postdeposition treatment (KF PDT) of Cu(In,Ga)Se-2 (CIGS) thin films has led to the achievement of several consecutive new world record efficiencies up to 21.7% for the CIGS solar cell technology. The beneficial effect of the KF PDT on the photovoltaic parameters was observed by several groups in spite of differing growth methods of the CIGS layer. For CIGS evaporated at lower temperature on alkali-free, flexible plastic substrates, a postdeposition treatment to add Na was already successfully applied. However, with the introduction of additional KF under comparable conditions, distinctly different influences on the final absorber alkali content as well as surface properties are observed. In this work we discuss in more detail the intrinsically different role of both alkali-treatments by combining several microstructural and compositional analysis methods. The ion exchange of Na by K in the bulk of the absorber is carefully analyzed, and further evidence for the formation of a K-containing layer on the CIGS surface with increased surface reactivity is given. These results shall serve as a basis for the further understanding of the effects of alkali PDT on CIGS and help identify research needs to achieve even higher efficiencies.

High mobility hydrogenated indium oxide is investigated as a transparent contact for thin film Cu(In,Ga)Se2 (CIGS) solar cells. Hydrogen doping of In2O3 thin films is achieved by injection of H2O water vapor or H2 gas during the sputter process. As-deposited amorphous In2O3:H films exhibit a high electron mobility of ∼50 cm2/Vs at room temperature. A bulk hydrogen concentration of ∼4 at. % was measured for both optimized H2O and H2-processed films, although the H2O-derived film exhibits a doping gradient as detected by elastic recoil detection analysis. Amorphous IOH films are implemented as front contacts in CIGS based solar cells, and their performance is compared with the reference ZnO:Al electrodes. The most significant feature of IOH containing devices is an enhanced open circuit voltage (VOC) of ∼20 mV regardless of the doping approach, whereas the short circuit current and fill factor remain the same for the H2O case or slightly decrease for H2. The overall power conversion efficiency is improved from 15.7% to 16.2% by substituting ZnO:Al with IOH (H2O) as front contacts. Finally, stability tests of non-encapsulated solar cells in dry air at 80 °C and constant illumination for 500 h demonstrate a higher stability for IOH-containing devices.

Solution processing of Cu2ZnSn(S,Se)4 (CZTSSe)-kesterite solar cells is attractive because of easy manufacturing using readily available metal salts. The solution-processed CZTSSe absorbers, however, often suffer from poor morphology with a bilayer structure, exhibiting a dense top crust and a porous bottom layer, albeit yielding efficiencies of over 10%. To understand whether the cell performance is limited by this porous layer, a systematic compositional study using (scanning) transmission electron microscopy ((S)TEM) and energy-dispersive X-ray spectroscopy of the dimethyl sulfoxide processed CZTSSe absorbers is presented. TEM investigation revealed a thin layer of CdS that is formed around the small CZTSSe grains in the porous bottom layer during the chemical bath deposition step. This CdS passivation is found to be beneficial for the cell performance as it increases the carrier collection and facilitates the electron transport. Electron-beam-induced current measurements reveal an enhanced carrier collection for this buried region as compared to reference cells with evaporated CdS.

Large-grained CuInSe2 absorber layers are synthesized using a non-vacuum process based on nanoparticle ink precursors and selenization by rapid thermal processing (RTP). The use of hydroxide-based particles in organic solvents allows for the conversion with elemental selenium without the need to employ explosive and/or toxic H-2 or H2Se gasses. Lateral grain sizes up to 4 mu m are obtained through a novel RTP route, overcoming the inherently high layer porosity for previous nanoparticle processes. Morphological and elemental characterization at interrupted selenization steps suggests that liquid selenium can play a beneficial role in promoting layer densification and grain growth. Long carrier collection lengths in CuInSe2 enable notable conversion efficiencies, despite the low minority carrier lifetimes of below 1ns. Record efficiencies up to 8.73% highlight the potential of low-cost, non-vacuum deposition of chalcopyrite absorber layers with safe and simple precursors and processing routes. Copyright (c) 2014 John Wiley & Sons, Ltd.

Aluminum-doped zinc oxide (AZO) thin films are prepared by a low temperature (100 degrees C) aqueous solution deposition method with a subsequent UV post-deposition treatment at 140 degrees C. Film growth is governed by the retrograde solubility of zinc-ammine complexes at basic conditions (pH 11.4). Aluminum was introduced into the film as a dopant by co-precipitation, either using an aluminum metal foil or aluminum nitrate as a precursor. As the presence of Al ions in the solution influences the film morphology as well as the opto-electronic properties, different profiles of the dopant supply were examined and optimized with respect to the optical and electrical properties of the AZO layer. It was found that independent of the chosen aluminum precursor a linearly increasing dopant concentration in the solution is favorable for achieving dense, highly transparent (<8% absorption between 400 and 900 nm) AZO thin films with a lowest resistivity of 3.4 x 10(-3) Omega cm. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Solution processing of inorganic thin films has become an important thrust in material research community because it offers low‐cost and high‐throughput deposition of various functional coatings and devices. Especially inorganic thin film solar cells – macroelectronic devices that rely on consecutive deposition of layers on large‐area rigid and flexible substrates – could benefit from solution approaches in order to realize their low‐cost nature. This article critically reviews existing deposition approaches of functional layers for chalcogenide solar cells with an extension to other thin film technologies. Only true solutions of readily available metal salts in appropriate solvents are considered without the need of pre‐fabricated nanoparticles. By combining three promising approaches, an air‐stable Cu(In,Ga)Se2 thin film solar cell with efficiency of 13.8% is demonstrated where all constituent layers (except the metal back contact) are processed from solutions. Notably, water is employed as the solvent in all steps, highlighting the potential for safe manufacturing with high utilization rates.

Die zum Monatswechsel anstehende Ministerkonferenz der Welthandelsorganisation (WTO) bereitet nicht nur den Handelsdiplomaten in Genf, sondern auch zahllosen Mitgliedern Nichtregierungsorganisationen (NGOs) schon im Vorfeld schlaflose Nächte: In Seattle steht die richtungsweisende Entscheidung über den Rahmen und die Themen der nächsten WTO-Verhandlungen an, die Anfang 2000 beginnen werden.