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Evaporated charge extraction layers from organic molecular materials are vital in perovskite-based solar cells. For opto-electronic device optimization their complex refractive indices must be known for the visible and near infrared wavelength regime; however, accurate determination from thin organic films below 50 nm can be challenging. By combining spectrophotometry, variable angle spectroscopic ellipsometry, and X-ray reflectivity with an algorithm that simultaneously fits all available spectra, the complex refractive index of evaporated Spiro-TTB and C

Perovskite silicon tandem solar cells have the potential to overcome the efficiency limit of single-junction solar cells. For both monolithic and mechanically stacked tandem devices, a semi-transparent perovskite top solar cell, including a transparent contact, is required. Usually, this contact consists of a metal oxide buffer layer and a sputtered transparent conductive oxide. In this work, semi-transparent perovskite solar cells in the regular n-i-p structure are presented with tin-doped indium oxide (ITO) directly sputtered on the hole conducting material Spiro-OMeTAD. ITO process parameters such as sputter power, temperature, and pressure in the chamber are systematically varied. While a low temperature of 50 °C is crucial for good device performance, a low sputter power has only a slight effect, and an increased chamber pressure has no influence on device performance. For the 5 × 5 mm2 perovskite cell with a planar front side, a 105 nm thick ITO layer with a sheet resistance of 44 Ω sq-1 allowing for the omission of grid fingers and a MgF2 antireflection coating are used to improve transmission into the solar cells. The best device achieved an efficiency of 14.8%, which would result in 24.2% in a four-terminal tandem configuration.

The main advantages of the organic–inorganic halide perovskite solar cell technology are high efficiencies achieved after short development time in combination with rather simple solution-based processing. In this paper, we address remaining challenges by presenting a low-temperature two-step hybrid evaporation-spincoating method that combines high reproducibility with easy fabrication and high stabilized efficiencies, which is compatible with the processing of pervoskite silicon tandem solar cells and avoids using hazardous solvents such as dimethylformamide and dimethylsulfoxide. Lead iodide (PbI2) is thermally evaporated and subsequently converted into a compact crystalline perovskite layer by methylammonium iodide spincoating. Moreover, the role of the interface passivation between perovskite absorber and electron transport layer on crystallization and optoelectronic properties of the perovskite absorber is investigated within a systematic thickness and concentration variation of [6, 6]-phenyl-C61-butyric acid methyl ester passivation layer and by analyzing charge extraction with spatial and time resolved photoluminescence measurements. With an optimized charge extraction, 18.2% stabilized efficiency under one sun illumination is achieved. This is the highest value reported so far for the single junction perovskite solar cells made by a two-step hybrid evaporation-spincoating method.

Perovskite silicon tandem solar cells can exceed the efficiency limit of 29.4% of single junction silicon solar cells, with comparably low additional costs for depositing the layers for the perovskite solar cell. Hence, they are an attractive option to further decrease the costs of photovoltaic electricity generation. We present, how by optimizing perovskite absorber composition, choosing adequate carrier selective contact layers, introducing surface passivation and optimizing the individual layer thicknesses solar cell efficiencies above 25% can be realized experimentally. Furthermore, we discuss different options for reducing front surface reflection by anti-reflection coatings, structured foils and deposition on textured silicon wafers and their impact both on solar cell efficiency as well as on the yearly energy yield. Deposition on textured silicon wafers promises highest energy yield. Hence, we show how perovskite absorbers can be deposited on such substrates by either co-evaporation or hybrid processing combining evaporation and subsequent wet-chemical processing. By bottom up cost calculations we finally show how and under which conditions perovskite silicon tandem solar cells can yield an economic advantage.

Electroplated copper contacts on small-area single-junction perovskite solar cells (PSCs) using an atomic layer deposited (ALD) Al2O3 masking layer on ITO are demonstrated for the first time. The photoconversion efficiency of ≈11% after manufacturing the Cu contacts confirms that PSCs can survive the wet-chemical plating process. From the successful realization of plated contact fingers, the creation of an electrical contact between the Cu electrode and the ITO on the FA0.75Cs0.25Pb(I0.8Br0.2)3 perovskite absorber is inferred. Furthermore, scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) analysis shows the formation of a compact interface between ITO and plated Cu. An additional plating approach, using self-passivated aluminum as mask, allows to produce well-defined 30 mm wide Cu contacts on the PSC. Such a plating process allows for plating a low-resistive Cu grid simultaneously on both sides of a perovskite silicon heterojunction tandem solar cell with TCO, independent of substrate size.

Silicon-based tandem solar cells can overcome the efficiency limit of single junction silicon solar cells. Perovskite solar cells are particularly promising as a top cell in monolithic tandem devices due to their rapid development towards high efficiencies, a tunable band gap with a sharp optical absorption edge and a simple production process. In monolithic tandem devices, the perovskite solar cell is deposited directly on the silicon cell, requiring low-temperature processes ( 2 ) scaffold - a structure yielding the highest efficiencies for single-junction perovskite solar cells. We show that evaporation of the compact TiO 2 hole blocking layer and ultra-violet (UV) curing for the mesoporous TiO 2 layer allows for good performance, comparable to high-temperature (> 500°C) processes. With both manufacturing routes, we obtain short-circuit current densities (J SC ) of about 20 mA/cm², open-circuit voltages (V OC ) over 1 V, fill factors (FF) between 0.7 and 0.8 and efficiencies (η) of more than 15%. We further show that the evaporated TiO 2 layer is suitable for the application in tandem devices. The series resistance of the layer itself and the contact resistance to an indium doped tin oxide (ITO) interconnection layer between the two sub-cells are low. In addition, the low parasitic absorption for wavelengths above the perovskite band gap allow a higher absorption in the silicon bottom solar cell, which is essential to achieve high tandem efficiencies.

The most efficient organic–inorganic perovskite solar cells (PSCs) contain the conventional n-i-p mesoscopic device architecture using a semiconducting TiO2 scaffold combined with a compact TiO2 blocking layer for selective electron transport. These devices achieve high power conversion efficiencies (15–22%) but mainly require high-temperature sintering (>450 °C), which is not possible for temperature-sensitive substrates. Thus far, comparably little effort has been spent on alternative low-temperature (

Homogeneous layer formation on textured silicon substrates is essential for the fabrication of highly efficient monolithic perovskite silicon tandem solar cells. From all well-known techniques for the fabrication of perovskite solar cells (PSCs), the evaporation method offers the highest degree of freedom for layer-by-layer deposition independent of the substrate's roughness or texturing. Hole-transporting polymers with high hole mobility and structural stability have been used as effective hole-transporting materials (HTMs) of PSCs. However, the strong intermolecular interactions of the polymers do not allow for a layer formation via the evaporation method, which is a big challenge for the perovskite community. Herein, we first applied a hole-transporting terthiophene polymer (PTTh) as an HTM for evaporated PSCs via an in situ vapor-phase polymerization using iodine (I

Recently, hybrid processing using evaporation and spin-coating has been applied for the fabrication of perovskite silicon tandem solar cells with record power conversion efficiencies (PCEs) of 25.2%. To achieve large area, high-throughput production of solar cells, spray-coating, a well-known scalable method used in the industry, has advantages over spin-coating. Therefore, we apply a hybrid method using the evaporation of PbI2 and spraying of methylammonium iodide (MAI) for the fabrication of perovskite solar cells. This article presents a systematic study of sprayed MAI amount and processing parameters on the performance of solar cells. We find clear correlations between the processing parameters of the sprayed MAI, the crystallinity of CH3NH3PbI3 and the PCE of the resulting PSCs. High crystallinity and morphology of the CH3NH3PbI3 film is achieved using a slow nozzle speed of 30 mm·s−1. An average PCE of 11.6% ± 3.1% (maximum PCE of 14.3%, stabilized PCE of 10%) was achieved with a normalized MAI amount of 3.4, which represent the flow rate of 0.17 ml·min−1, nozzle speed of 30 mm·s−1, MAI concentration of 9 mg·mL−1, and one single spray pass. Moreover, we successfully show a proof-of-concept of this method for the deposition of homogenous perovskite layers on pyramidal textured silicon.

Low electrode impedance paired with low catalyst loading in intermediate and low temperature fuel cells is extremely difficult to achieve, posing a major obstacle to commercialization. Here we demonstrate a scalable and facile route to obtain nanostructured composite solid acid fuel cell electrodes consisting of Pt decorated carbon nanotubes and CsH2PO4 microparticles as the electrolyte. Electrochemical impedance measurements in humidified hydrogen at 240 °C show very low 0.05 Ω cm2 area normalized electrode resistance, with a Pt loading of only 0.41 mgPt cm−2. This is a reduction of the Pt loading by more than one order of magnitude paired with even lower electrode impedance values compared to the current state-of-the-art in literature. Fuel-cell measurements show remarkably stable electrode performance over a 17 h period with a final degradation rate of 0.1% h−1.

Most efficient perovskite solar cells are synthesized by the one-step spin coating method. However, when applied on µm-sized textures, e.g. for efficient monolithic perovskite silicon tandems, no conformal film formation is achieved. In this respect, we investigate hybrid evaporation/ spin coating for mixed cation mixed halide perovskite absorbers [HC(NH2)2]0.83Cs0.17Pb(I1-xBrx)3 (x = 0–0.28). By control of the 2nd deposition step, we demonstrate systematic band gap tuning from 1.54 to 1.75 eV. Moreover, critical criteria for synthesis and underlying charge transport materials (CTM) are determined by investigation of planar as well as scaffolded electron transport layers. Regarding the applicability on textures, the tandem-relevant 1.7 eV high band gap absorber is deposited on planar, pyramidal, and spiky black silicon to investigate crystallization and layer formation dependent on the substrate's topography. We recommend the presented hybrid method for realization of dense crystalline perovskite films with flat surface, deposition on planar CTM, and textured Si-based tandems with random pyramids.

Monolithic perovskite silicon tandem solar cells can overcome the theoretical efficiency limit of silicon solar cells. This requires an optimum bandgap, high quantum efficiency, and high stability of the perovskite. Herein, a silicon heterojunction bottom cell is combined with a perovskite top cell, with an optimum bandgap of 1.68 amp; 8201;eV in planar p i n tandem configuration. A methylammonium free FA0.75Cs0.25Pb I0.8Br0.2 3 perovskite with high Cs content is investigated for improved stability. A 10 molarity increase to 1.1 amp; 8201;m of the perovskite precursor solution results in amp; 8776;75 amp; 8201;nm thicker absorber layers and 0.7 amp; 8201;mA amp; 8201;cm amp; 8722;2 higher short circuit current density. With the optimized absorber, tandem devices reach a high fill factor of 80 and up to 25.1 certified efficiency. The unencapsulated tandem device shows an efficiency improvement of 2.3 absolute over 5 amp; 8201;months, showing the robustness of the absorber against degradation. Moreover, a photoluminescence quantum yield analysis reveals that with adapted charge transport materials and surface passivation, along with improved antireflection measures, the high bandgap perovskite absorber has the potential for 30 tandem efficiency in the near future

The most efficient organic-inorganic perovskite solar cells (PSCs) contain the conventional n-i-p mesoscopic device architecture using a semiconducting TiO

Perovskite silicon tandem solar cells can overcome the efficiency limit of single junction solar cells. For an optimized optical performance, we propose a 2-terminal device featuring a front-side anti-reflection structure, optimized layer thicknesses, a meso-porous scaffold for the perovskite solar cell and a rear-side light-trapping structure for the silicon solar cell. To maintain the functionality of the underlying layers, we have developed a low-temperature process to realize a meso-porous TiO 2 scaffold via ultra-violet (UV) curing. With perovskite solar cell efficiencies >;150/0, we achieve results comparable to our conventional high-temperature (>; 500°C) route. For the optical optimization of the complex tandem device with elements of different feature sizes, we apply a matrix-based formalism and show how layer thickness optimization and the rear-side light trapping can significantly improve the current of the tandem device.

To realize high efficiency monolithic perovskite silicon tandem solar cells, we develop low-temperature processes for the perovskite top cell, rear-side light trapping, optimized perovskite growth, transparent contacts and recombination interconnection layers, and adapted characterization methods.

The capacity of several coat protein (CP) mutants of a German isolate of barley yellow mosaic bymovirus (BaYMV) to bind of nucleic acids was studied in vitro. Recombinant CP, produced by overexpression in Escherichia coli, was purified from inclusion bodies and subsequently renatured. Binding to single-stranded (ss) RNA and ssDNA oligonucleotides was found to be cooperative and sequence non-specific. By deletion mutagenesis, several truncated CP derivatives were created and their nucleic acid-binding capacity was investigated in order to define a protein domain responsible for RNA- and DNA-binding. The nucleic acid-binding domain consists of a core which was located to an internal 23 amino acid peptide (aa 125-147) and an adjacent domain (aa 148-184) which stimulates binding.

Summary A “resistance breaking” isolate of barley yellow mosaic virus-2 (BaYMV-2) was cloned as a cDNA and characterised. Restriction mapping and comparison with a German and a Japanese isolate of BaYMV (BaYMV-G and BaYMV-J) revealed a high level of restriction site conservation for RNAl and the majority of RNA2. However, in a box of approximately 600 nucleotides located on RNA2, striking differences in the restriction pattern could be identified. The nucleotide sequence of this box, as well as of the 3‘-terminal region of RNA1 including the coat protein coding region, and the deduced amino acid sequences were analysed. Identity at the amino acid level was between 99.3% and 92.3% in comparison with the corresponding sequences of BaYMV-G and BaYMV-J, suggesting that BaYMV-2 is closely related to BaYMV. Consequently, the classification of BaYMV-2 as a “resistance breaking” strain of BaYMV is justified.

The iaaL gene of Pseudomonas syringae subsp. savastanoi encodes an indoleacetic acid-lysine synthetase that conjugates lysine to indoleacetic acid. A chimaeric gene consisting of the iaaL coding region under the control of the 35S RNA promoter from cauliflower mosaic virus (35SiaaL) has been used to test if iaaL gene expression leads to morphological alterations in tobacco and potato. Transgenic tobacco plantlets bearing this construct have been shown to synthesize IAA-[14C]lysine when fed with [14C]lysine. In late stages of development, their leaves show an increased nastic curvature (epinasty) of the petiole and midvein, a finding suggestive of an abnormal auxin metabolism. The alteration is transmitted to progeny as a dominant Mendelian trait cosegregating with the kanamycin resistance marker. Transgenic potato plants harbouring the construct are also characterised by petiole epinasty. Moreover, 35SiaaL transgenic plants have an increased internode length in potato and decreased root growth in both tobacco and potato. An increased content of IAA-conjugates in leaf blade was found to correlate with the epinastic alterations caused by iaaL gene expression in tobacco leaves. These data provide evidence that IAA conjugation is able to modulate hormone action, suggesting that the widespread endogenous auxin-conjugating activities are of physiological importance.

Chimaeras are genetic mosaics composed of intermixed genetically different tissues. Transposable elements can be used to activate gene expression in clonal populations of cells and consequently to generate genetic mosaics. To achieve this a gene of interest (e.g. morphogenetic genes from plant pathogens) is split by a transposable element in such a way that excision events will reactivate gene expression in transgenic plants. Excision events taking place late during plant organ development will generate extra-apical mosaics composed of intermixed tissues with wild-type and mutant phenotype. In particular, the use of a transposon-split 35sipt gene to raise plants transgenic for a cytokinin synthetising gene, whose constitutive expression is not compatible with plant regeneration is presented. Moreover we have constructed a chimaeric gene composed of the 35s RNA promoter of cauliflower mosaic virus and the indoleacetic-acid lysine synthetase of Pseudomonas savastanoi and defined the morphological alterations established by iaal gene expression in transgenic plants.

In monolithic perovskite/silicon tandem solar cells, it is important to know which sub-cells is limiting the overall current to adapt the perovskite absorber thickness and bandgap accordingly. The current matching situation is usually analyzed by integrating measured external quantum efficiencies. However, this method can lead to significant errors and misinterpretations if meta-stable perovskite solar cells are involved. In this work, spectrometric characterization is presented as an alternative approach avoiding these errors. Current-voltage curves are recorded under different spectral conditions. Spectral irradiance settings are varied in a systematic way from red-shifted spectra (the perovskite top solar cell limits the current) to blue-shifted spectra (the silicon bottom solar cell limits the current) around the Air Mass 1.5 global (AM1.5g) spectrum. This method not only allows for accurate determination of the current matching point, but also gives quantitative insight in the behavior of the single sub-cells and their influence on the tandem performance. As different current mismatching also influences other global cell parameters, an example is presented where the current loss due to the current mismatch is partly compensated by a strong fill factor increase when the silicon solar cell limits the current, resulting in a high-power output also at the AM1.5g condition.