Iver Lauermann

Iver Lauermann
Helmholtz-Zentrum Berlin | HZB · PVcomB

Dr.

About

202
Publications
26,862
Reads
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4,872
Citations
Citations since 2017
58 Research Items
2139 Citations
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20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
Additional affiliations
January 2002 - present
Helmholtz-Zentrum Berlin
Position
  • Thin film solar cell research
January 2002 - March 2016
Helmholtz-Zentrum Berlin
Position
  • Head of Department
August 1998 - July 2000
Freie Universität Berlin
Position
  • Researcher

Publications

Publications (202)
Presentation
Full-text available
Oral communication participation in the 2nd edition of PhotOnline conference organized by the Société Chimique de France (SCF)/French Chemical Society, specifically the Photochemistry, Photophysics, and Photosciences division.
Article
High-performing materials will dictate the pace of reinventing industrial chemical processes to achieve carbon neutrality. Visible-light photoelectrocatalysts from abundant resources will play a key role in exploiting solar irradiation. Anionic doping via pre-organization of precursors and further co-polymerization creates tuneable, extrinsic semic...
Article
Full-text available
Sustainable, high-performance carbonaceous anode materials are highly required to bring sodium-ion batteries on a more competitive level. Here, we exploit our expertise to control the deposition of a nm-sized conformal coating of carbon nitride with tunable thickness to improve the electrochemical performance of carbon materials derived from lignos...
Preprint
Full-text available
Novel high performing materials will dictate the pace of reinventing industrial chemical processes to attain desired carbon neutrality targets. Regarding the urgency of exploiting solar irradiation long range visible-light photoelectrocatalysts from abundant resources will play a key role in the aforementioned effort. Anionic doping via co-polymeri...
Preprint
Full-text available
Novel high performing materials will dictate the pace of reinventing industrial chemical processes to attain desired carbon neutrality targets. Regarding the urgency of exploiting solar irradiation long range visible-light photoelectrocatalysts from abundant resources will play a key role in the aforementioned effort. Anionic doping via co-polymeri...
Poster
Full-text available
This work contributes to the development of amorphous sulfur-doped carbon nitride photoelectrocatalysts with long-visible-light range for solar energy conversion and storage.
Article
Transparent conductive materials based on indium oxide remain yet irreplaceable in various optoelectronic applications. Amorphous oxides appear especially attractive for technology as they are isotropic, demonstrate relatively high electron mobility and can be processed at low temperatures. Among them is indium zinc oxide (IZO) with a large zinc co...
Article
Full-text available
Carbon laser‐patterning (CLaP) is emerging as a new tool for the precise and selective synthesis of functional carbon‐based materials for on‐chip applications. The aim of this work is to demonstrate the applicability of laser‐patterned nitrogen‐doped carbon (LP‐NC) for resistive gas‐sensing applications. Films of pre‐carbonized organic nanoparticle...
Article
Full-text available
Understanding the oxygen evolution reaction (OER) activity and stability of the NiFe-based materials is important for achieving low-cost and highly efficient electrocatalysts for practical water splitting. Here, we report the roles of Ni and Fe on the OER activity and stability of metallic NiFe and pure Ni thin films in alkaline media. Our results...
Article
In conventional Cu(In,Ga)Se2 (CIGSe) solar cells a chemical bath deposited CdS thin film is used as a buffer layer. However, it is desired to replace CdS due to the toxicity of cadmium and the rather narrow bandgap energy of CdS. Zn(O,S) is considered to be one of the most attractive candidates as an alternative, non-toxic buffer layer with a large...
Article
Approaches to boost the efficiency and stability of perovskite solar cells often address one singular problem in a specific device configuration. In this work, we utilize a poly(ionic-liquid) (PIL) to...
Article
Full-text available
Current perovskite solar cell efficiency is close to silicon's record values. Yet, the roadblock for industrialization of this technology is its stability. The stability of the solar cell not only depends on the stability of the perovskite material itself but also notably on its contact layers and their interface with the perovskite, which plays a...
Article
Hard X-ray photoelectron spectroscopy Glow discharge optical emission spectrometry Alkali treatment Rubidium fluoride A B S T R A C T Photovoltaic devices based on Cu(In,Ga)Se 2 (CIGSe) absorbers are among the most attractive non-Si alternatives. The key to their steadily increasing efficiency is a post-deposition treatment (PDT) with alkali salts....
Article
Full-text available
Selective modification of the morphology and intrinsic electrocatalytic activity of porous electrodes is urgently required to improve the performance of vanadium redox flow batteries (VRFBs). For this purpose, electrospinning was exploited to prepare high-performance nanofiber-based composites. Blends of polyacrylonitrile, polyacrylic acid and poly...
Article
The cover image is based on the Research Article A European proficiency test on thin‐film tandem photovoltaic devices by Elena Salis et al., https://doi.org/10.1002/pip.3322.
Article
In this work, the alkali-induced chemical and electronic modifications observed at the KF- and RbF-treated Cu (In,Ga)Se2 (CIGSe)/CdS interfaces are correlated to a Density Functional Theoretical (DFT) model of the alkali metal induced point defects at a CuInSe2/CdS interface. Analysed with hard X-ray photoelectron spectroscopy (HAXPES), the near-in...
Article
Full-text available
A round‐robin proficiency test (RR PT) on thin‐film multi‐junction (MJ) photovoltaic (PV) cells was run between 13 laboratories within the European project CHEETAH. Five encapsulated PV cells were circulated to participants for being tested at Standard Test Conditions (STC). Three cells were a‐Si/μc‐Si tandem PV devices, each of which had a differe...
Article
The compound semiconductor Zn1-xCoxO (x = 0.42; ZnO:Co) has recently gained interest as a highly active electrocatalyst material for water oxidation (WOCs). We report on the significant structural and electronic transformations under anodic oxygen evolution reaction conditions of a novel, large area scalable sputtered ZnO:Co electrocatalyst. ZnO:Co...
Article
Sodium is known to play a crucial role in thin-film solar cells based on Cu(In,Ga)Se2 (CIGSe) absorbers, however, the chemical state of Na in CIGSe is still under discussion. In this work, an Auger parameter analysis has been carried out to identify the differences in the chemical states of Na in CIGSe, originating from two different sources: the s...
Article
Full-text available
Hydrogenation reactions in water at elevated temperatures are challenging for heterogeneous catalyst. Thus, we present a simple, cheap, scalable, and sustainable approach for synthesizing an efficient and water-tolerant Ni catalyst supported on highly porous nitrogen-doped carbon (NDC) in pellet shape. The performance of this catalyst was evaluated...
Article
Many nanofabrication processes require sophisticated equipment, elevated temperature, vacuum or specific atmospheric conditions, templates, and exotic chemicals, which severely hampers their implementation in real-world applications. In this study, we outline a fully wet-chemical procedure for equipping a 3D carbon felt (CF) substrate with a multif...
Article
The molecular arrangement of vacuum thermally deposited polycrystalline Zn-phthalocyanine (ZnPc) layers on Si substrates is investigated using near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy in the proximity of the carbon edge at E0 = 287.33 eV. The data were collected as a function of the deposition substrate temperature TS (30, 90...
Article
Full-text available
Correction for ‘Hierarchically structured iron-doped silver (Ag–Fe) lotus flowers for an efficient oxygen reduction reaction’ by Gumaa A. El-Nagar et al. , Nanoscale , 2018, 10 , 7304–7310.
Article
Tailoring of nanostructured materials with well-controlled morphologies and their integration into valuable applications in a facile, cheap and green way remains a key challenge. Herein, platinum nanoparticles as well as Pt-polymer nanocomposites with unique shapes, including flower-, needle-, porous- and worm-like structures, were synthesized and...
Article
A UHV-transferred Cu(In,Ga)Se2 (CIGSe) thin film prepared by a three-stage process on an Mo-coated float glass was successfully investigated by detailed UPS/XPS and directly compared with air-transferred and cyanide etched samples from the same batch. Besides the fact that the valence band maximum of the UHV-transferred sample is located 1.19 eV be...
Article
Surface doped indium tin oxide (ITO)/graphene systems as a hole transporting transparent front electrode in electro-optical applications are potential alternatives to conventional ITO with wet chemically prepared polymers. In this paper we investigate, firstly, chemical impurities of chemical vapor deposition prepared graphene transferred onto glas...
Article
Perovskite-based tandem solar cells can increase the power conversion efficiency (PCE) of conventional single-junction photovoltaic devices. Here, we present monolithic perovskite/CIGSe tandem solar cells with a perovskite top cell fabricated directly on an as-grown, rough CIGSe bottom cell. To prevent potential shunting due to the rough CIGSe surf...
Article
Full-text available
The crystallisation of sputter-deposited, amorphous In2O3:H films was investigated. The influence of deposition and crystallisation parameters onto crystallinity and electron hall mobility was explored. Significant precipitation of metallic indium was discovered in the crystallised films by electron energy loss spectroscopy. Melting of metallic ind...
Article
In order to surpass the theoretical limitation defined by the Shockley–Queisser equation for photovoltaic solar cells, multijunction devices are needed. Monolithic perovskite‐Cu(In, Ga)(Se, S)2 (CIGSe) tandem solar cells have recently become a hot research topic in photovoltaics because of the emergence of perovskite solar cells with high power con...
Article
Latest record efficiencies of Cu(In,Ga)Se2 (CIGSe) solar cells were achieved by means of a rubidium fluoride (RbF) post-deposition treatment (PDT). To understand the effect of the RbF-PDT on the surface chemistry of CIGSe and its interaction with sodium that is generally present in the CIGSe absorber, we performed an X-ray photoelectron spectroscop...
Article
This paper addresses the damaging role of the parasitic hydrogen evolution reaction (HER) in the negative half-cell of a vanadium redox flow battery (VRFB) on state-of-the-art carbon felt electrodes at different temperatures. It was found that increasing the temperature resulted in a better catalytic performance for both the positive and negative h...
Article
Full-text available
The impact of a rubidium fluoride post deposition treatment (RbF‐PDT) on the material and device properties of Cu(In,Ga)Se2 (CIGS) thin films and corresponding solar cells is investigated. The structure and device properties of CIGS with different PDT duration are compared. With longer PDT duration, which equals a higher amount of RbF deposited on...
Article
Developing cheap and efficient electrocatalysts for the oxygen reduction reaction (ORR) is vital for the immediate commercialization of fuel cells which are still limited by the high cost and low performance of the utilized commercial Pt-based electrodes. As a promising alternative, this study reports on the synthesis of hierarchical iron-doped sil...
Article
Either metallic Na or NaF were deposited onto Cu(In,Ga)Se2 surfaces and studied by photoelectron spectroscopy and surface photovoltage spectroscopy without breaking the ultra-high vacuum. The deposition of elemental Na at room temperature led to the formation of an intermediate Cu and Ga rich layer at the CIGSe surface, whereas for NaF the composit...
Article
Full-text available
Carbon dots have attracted much attention due to their unique optical, chemical and electronic properties enabling a wide range of applications. Carbon dots’ properties can be effectively adjusted through modifying their chemical composition. However, a major challenge remains in understanding the core and surface contributions to optical and elect...
Article
Full-text available
Commercial Pt/C anodes of direct formic acid fuel cells (DFAFCs) get rapidly poisoned by in-situ generated CO intermediates. We succeeded in increasing the Pt nanoparticles (PtNPs) stability and activity for formic acid oxidation (DFAFCs anodic reaction) by embedding them inside a chitosan matrix obtained from seafood wastes. Atop the commercial Pt...
Conference Paper
Full-text available
The influence of a KF-treatment of Cu(In,Ga)Se2 absorbers alone, without the influence of an excessive Se atmosphere and Na from the glass substrate has been studied. K-induced surface modifications differed for varying [K]/([In]+[Se]) (KIS) concentration ratios with a low KIS (0.74) absorber having a K-alloyed CIGSe surface growth and a high KIS (...
Article
Na and K metals have been evaporated on a Cu(In,Ga)Se2 (CIGSe) thin film solar cell absorber at 400 °C in order to investigate the effect of alkali metal incorporation on the very near-surface (up to 5 nm) region of the CIGSe absorber using soft X-ray spectroscopy techniques, focusing on the main compositional and electronic modifications of the ab...
Experiment Findings
Electrografting of Selected Diazonium Salts as a facile route for surface modification by chelating ligands.
Article
Constructing tandem junction devices consisting of a bottom cell based on prevailing solar cell techniques such as silicon (Si) or Cu(In,Ga)(Se,S)2 (CIGS) combined with a perovskite top cell is one effective approach to improve photovoltaic device performance. An intermediate transparent conducting layer as one component of the tunnel junction conn...
Article
Full-text available
We present an efficient non-enzymatic hydrogen peroxide sensor composed of flower-like silver microstructures. The silver microstructures´ morphology is controlled by adding minute amounts of either succinic or malonic acid as directing agents. Morphologically, silver particles showed ball-like structures in the absence of both directing agents, wh...
Article
Thin film solar cells based on the kesterite material with the general composition Cu2ZnSn(Se,S)4 can be a substitute for the more common chalcopyrites (Cu(In,Ga)(Se,S)2) with a similar band gap range. When replacing the anion sulfide with selenide, the optical band gap of kesterite changes from 1.5 to 1 eV. Here we report on a study of the valence...
Article
Inkjet printing is a promising route for thin film deposition due to its low material wastage and potential of high throughput production. In this work, the inkjet printing technique is used for the deposition of Cu2ZnSn(SxSe1-x)4 (CZTSSe) thin films from Cu-Zn-Sn-S molecular inks. The key step for using the inkjet printing technique is to formulat...
Poster
Heavy metal ion (HMI) pollutants are a threat to fresh water supplies and marine ecosystems [1]. Copper (Cu) can be highly toxic especially to aquatic ecosystems [2]. Silicon (Si) is an abundant material on the earth’s crust and coupled with its semiconducting properties, it can also permit development of sensors that exploit ligand-analyte interac...
Article
Metal ion chelating property was conferred onto silicon (Si) and gold (Au) surfaces by direct electrografting of 4-[(carboxymethyl)thio]benzenediazonium cation (4-CMTBD). Infrared spectroscopic ellipsometry (IRSE) showed presence of characteristic phenyl and carbonyl vibrational bands on the functionalized surfaces as a proof of existence of surfac...
Article
The development of efficient and durable Pt-free catalysts for the oxygen reduction reaction (ORR) is extremely important to realize the worldwide commercialization of clean energy technologies obstructed by the high cost and scarcity of the Pt-based catalysts. As a potential alternative to such catalysts, this investigation addresses the facile sy...
Article
Multifunctional Ti4O7 particles with interconnected-pore structure are designed and synthesized using porous poly(styrene-b-2-vinylpyridine) particles as a template. The particles can work efficiently as a sulfur-host material for lithium–sulfur batteries. Specifically, the well-defined porous Ti4O7 particles exhibit interconnected pores in the int...
Article
We demonstrate that a simple and low-cost industrial sputter process can be used to substitute the InxSy:Na buffer and intrinsic ZnO layer with a single film of Zn(O,S). Cu(In,Ga)(Se,S)2 (CIGS) modules with an aperture area of 667 cm² and efficiencies up to 15.6% were prepared using a sputtered Zn(O,S) buffer layer. In comparison with our InxSy:Na...
Article
Full-text available
Spectral dependent charge transfer and exciton dissociation have been investigated at hybrid interfaces between inorganic polycrystalline CuInSe2 (untreated and Na-conditioned) thin films and organic C60 as well as zinc phthalocyanine (ZnPc) layers by transient and modulated surface photovoltage measurements. The stoichiometry and electronic proper...
Article
Full-text available
The impact of the potassium fluoride post deposition treatment on CIGSe chalcopyrite absorbers is investigated by means of depth resolved hard x-ray photoemission spectroscopy of the near surface region. Two similar, slightly Cu-poor CIGSe absorbers were used with one being treated by potassium fluoride prior to the chemical bath deposition of an u...
Article
Platinum and iridium polycrystalline foils were oxidized electrochemically through anodization to create thin platinum and iridium hydrous oxide layers, which were analyzed through laboratory photoelectron spectroscopy during heating and time series (temperature-programmed spectroscopy). The films contain oxygen in the form of bound oxides, water,...
Article
For a long time, it has been assumed that recombination in the space-charge region of copper-indium-gallium-selenide (CIGS) is dominant, at least in high efficiency solar cells with low band gap. The recent developments like potassium fluoride post deposition treatment and point-contact junction may call this into question. In this work, a theoreti...
Article
Full-text available
The CISSY end station combines thin film deposition (sputtering, molecular beam epitaxy ambient-pressure methods) with surface and bulk-sensitive analysis (photo emission, x-ray emission, x-ray absorption) in the same UHV system, allowing fast and contamination–free transfer between deposition and analysis. It is mainly used for the fabrication and...
Article
Cu2SnZn(S,Se)4 (CZTSSe) solar cells based on earth abundant and non-toxic elements currently achieve efficiencies exceeding 12%. It has been reported that to obtain high efficiency devices, a post thermal treatment of absorbers or devices at temperatures ranging between 150-400 ºC (post low temperature treatment, namely PLTT) is advisable. Recent f...
Article
Full-text available
Kesterite Cu2ZnSn(S,Se)4 absorber layers with different [S]/([S]+[Se]) ratios were studied using XPS, UPS, Hard X-ray (HIKE) photoemission and the Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS). The samples were prepared by IREC using sequentially sputtered metallic precursor stacks with metal ratios of [Cu]/([Zn]+[Sn])=0.80, [Zn]/...
Article
We report the development of Cd-free buffers by atomic layer deposition for chalcopyrite-based solar cells. Zn(O,S) buffer layers were prepared by atomic layer deposition on sequentially grown Cu(In,Ga)(Se,S)2 absorbers from Bosch Solar CISTech GmbH. An externally certified efficiency of 16.1% together with an open circuit voltage of 612 mV were ac...
Article
A combination of undoped ZnO and ZnO:Al is the most commonly used window layer stack for chalcopyrite solar cells. The high carrier density and thickness required to achieve a sufficiently low sheet resistance lead to optical absorption and cause losses in photocurrent, in particular in monolithically interconnected modules. Additionally, the band...
Conference Paper
Full-text available
This work describes novel procedures to grow Cu2ZnSnS4 (CZTS) thin films using vacuum and solution based methods. The solution based approach includes sequential deposition of Cu2SnS3 (CTS) and ZnS films, where the CTS compound is synthesized in a one step process by simultaneous precipitation of Cu2S and SnS2 in a thiosulphate solution, using diff...
Conference Paper
Full-text available
FP7-CHEETAH is a combined collaborative project (CP) and coordination and support action (CSA) funded under the European Commission’s 7th Framework program and coordinated by ECN, NL with the aims to solve specific R&D issues and to overcome fragmentation of European PV R&D by intensifying the collaboration between R&D providers and industry to acc...
Article
Integration of plasmonic Ag nanoparticles as a back reflector in ultra-thin Cu(In,Ga)Se2 (CIGSe) solar cells is investigated. X-ray photoelectron spectroscopy results show that Ag nanoparticles underneath a Sn:In2O3 back contact could not be thermally passivated even at a low substrate temperature of 440 °C during CIGSe deposition. It is shown that...
Article
A detailed study explaining the beneficial effects of low temperature postdeposition annealing combined with selective surface etchings for Cu2ZnSnSe4 (CZTSe) based solar cells is presented. After performing a selective oxidizing surface etching to remove ZnSe secondary phases typically formed during the synthesis processes an additional 200 °C ann...