Iver Lauermann

• Dr.
• Group Leader at Helmholtz-Zentrum Berlin für Materialien und Energie

The influence of minimal amounts of Ag (0.5–1.4 at%) on elemental distribution and crystalline quality of (Ag,Cu)(In,Ga)Se 2 (ACIGSe) absorbers grown by the three‐stage coevaporation without added alkali elements is reported. The elemental ratios affect the amount of Ag to be uniformly incorporated into the chalcopyrite absorber and the open‐circui...

For the commercialization of perovskite solar cells (PSCs), detection of associated degradation mechanisms and mitigation of their effect is of paramount importance. The former requires outdoor and indoor stability tests to detect these mechanisms under real operation conditions and to accelerate them under controlled environments. Herein, the ther...

Scope Decarbonization requires sustainable chemical conversion and renewable energies.{1} Novel high-performance materials will reshape industrial chemical processes. Anionic doping enables nanoarchitecture customization of carbon nitride (C3N4) structural, geometric, electrical, and optical properties.{2} Unconventional aminotriazoles (enhancers o...

Replacing the oxygen evolution reaction with other less energy-intense oxidizing reactions is an attractive option to reduce the energy demand for hydrogen production in an anion exchange membrane (AEM) water electrolyzer using transition metals and their alloys. Since urea is commonly available as a waste product, pairing the urea oxidation at the...

The 50M-50P hybrid catalyst exhibited the highest photooxidation conversion (84±3 %), is attributed to the shoulder (≈700 nm), the high sulfur content (1.6 wt. %), the homogeneous doping by substituting N atoms, low porosity, new intra band energy states, structural defects (layer distortion), flat morphology, hydrophobic surface.

Developing high‐performance carbonaceous anode materials for sodium‐ion batteries (SIBs) is still a grand quest for a more sustainable future of energy storage. Introducing sulfur within a carbon framework is one of the most promising attempts toward the development of highly efficient anode materials. Herein, a microporous sulfur‐rich carbon anode...

Nickel oxide (NiO 1+δ ) is a versatile material used in various fields such as optoelectronics, spintronics, electrochemistry, and catalysis which is prepared with a wide range of deposition methods. Herein, for the deposition of NiO 1+δ films, the reactive gas flow sputtering (GFS) process using a metallic Ni hollow cathode is developed. This tech...

The performance of five hole‐transporting layers (HTLs) is investigated in both single‐junction perovskite and Cu(In, Ga)Se2 (CIGSe)‐perovskite tandem solar cells: nickel oxide (NiOx,), copper‐doped nickel oxide (NiOx:Cu), NiOx+SAM, NiOx:Cu+SAM, and SAM, where SAM is the [2‐(3,‐6Dimethoxy‐9H‐carbazol‐9yl)ethyl]phosphonic acid (MeO‐2PACz) self‐assem...

We present monolithic 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. A champion efficiency of 23.2%, open-circuit voltage ( V oc ) of 1.69V, and a fill factor ( FF ) of 78.3% are achieved for the tandem with N 2 -transferred NiO x :Cu + SAM. Th...

Towards solar energy utilization, visible-light catalyst are more appealing than ever. Among several existing materials strategies, anionic doping is one attractive. Nevertheless, the atomic insertion into carbon nitride lattice is still limited. Here we have introduced up to 2% wt.% of highly dispersed and homogeneous sulfur atoms with promising f...

Towards solar energy utilization, visible-light catalyst are more appealing than ever. Among several existing materials strategies, anionic doping is one attractive. Nevertheless, the atomic insertion into carbon nitride lattice is still limited. Here we have introduced up to 2% wt.% of highly dispersed and homogeneous sulfur atoms with promising f...

Materials dictate carbon neutral industrial chemical processes. 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 semiconductors. Triazole derivative-purpald, an unexplored precursor with s...

We investigate the performance of monolithic copper-indium-gallium-selenide (CIGS)/perovskite tandem solar cells with two different CIGS bottom device absorbers: Cu(In,Ga)Se2 or Cu(In,Ga)(S,Se)2 and with three different hole-transporting layers (HTLs): NiOx + SAM, NiOx:Cu + SAM and SAM alone. NiOx(:Cu) is (2 wt% copper-doped) nickel oxide and SAM i...

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.

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...

Twitter conference involving the Latin American chemical community

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...

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...

This work contributes to the development of amorphous sulfur-doped carbon nitride photoelectrocatalysts with long-visible-light range for solar energy conversion and storage.

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...

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...

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...

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...

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...

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...

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....

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...

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.

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...

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...

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...

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...

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...

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...

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.

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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 (...

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...

Electrografting of Selected Diazonium Salts as a facile route for surface modification by chelating ligands.

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...

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...

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...

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...

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...

Modification of Surfaces for Cu Trapping Applications

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...

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...

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...

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...

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...

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...

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,...

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...

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...

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...

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]/...

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...

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...

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...

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...

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...

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...

The unusual defect chemistry of polycrystalline Cu(In,Ga)Se2 (CIGSe) thin films is a main issue for a profound understanding of recombination losses in chalcopyrite thin film solar cells. Especially impurity driven passivation of electronic levels due to point defects segregating at the surface and at grain boundaries is extensively debated. By com...

We have investigated a specially grown Cu(In,Ga)Se2 (CIGSe) absorber, which was deposited by co-evaporation of Cu, In, Ga, and Se using a modified three stage process. Prior to the growth, the molybdenum-coated glass substrate was covered by a bent shroud made from tantalum (Ta), leading to a wedged absorber structure with a width of about 2 mm whe...

In2S3 thin layers can be prepared by Spray-ILGAR® (Ion Layer Gas Reaction) from indium trichloride or from indium triacetylacetonate solutions. In the first case, the film contains a controllable amount of Cl. The concentration of H2O or Cl was varied systematically in the precursor solutions that were used for the deposition of In2S3 buffer layers...

The interface between CuInSe2 and i-ZnO as it is needed for new chalcopyrite concepts like superstrate and tandem solar cells is investigated with X-ray photoelectron spectroscopy. A specially developed preparation permits depth profiling of the underlying i-ZnO layer. Thereby, interfacial reactions are revealed by tracing the diffusion of Cu, In a...

Currently, Cu-containing chalcopyrite-based solar cells provide the highest conversion efficiencies among all thin-film photovoltaic (PV) technologies. They have reached efficiency values above 20%, the same performance level as multi-crystalline silicon-wafer technology that dominates the commercial PV market. Chalcopyrite thin-film heterostructur...

We report the effect of Cu(In,Ga)(Se,S)2 absorber surface treatments on the properties of atomic layer deposited-Zn(O,S) buffered 30 × 30 cm2 large area modules. The absorber is prepared by the sequential process. H2O and KCN solution treatments are investigated. The absorber surface treatment is found to influence significantly the open circuit vo...

A comparative study of the structural, optical and morphological properties of Cu2ZnSnS4 (CZTS) thin films prepared by two different techniques was performed. One consists of sequential evaporation of the elemental metallic precursors under a flux of sulphur supplied by evaporation from an effusion cell (physical vapor deposition-PVD) and the se...

Results regarding structural properties, chemical composition and oxidation states of Cu 2 ZnSnS 4 (CZTS) thin films prepared by co-evaporation are compared with those obtained with CZTS films grown by sequential deposition of Cu 2 SnS 3 (CTS) and ZnS thin films by CBD Process. CTS compound is prepared in one step process by simultaneous precipitat...

Optical and structural properties, chemical composition and oxidation states of Cu2ZnSnS4 (CZTS) thin films prepared by co-evaporation are compared with those of CZTS films grown by sequential deposition of Cu2SnS3 (CTS) and ZnS thin films, where the CTS compound is prepared in one step process by simultaneous precipitation of Cu2S and SnS2 perform...

Element-specific unoccupied electronic states of Cu(In, Ga)S2 were studied as a function of the In/ Ga ratio by combining X-ray absorption spectroscopy with density functional theory calculations. The S absorption edge shifts with changing In/Ga ratio as expected from the variation of the band gap. In contrast, the cation edge positions are largely...