Perovskite-organic tandem solar cells with indium oxide interconnect.

Multijunction solar cells can overcome the fundamental efficiency limits of single-junction devices. The bandgap tunability of metal halide perovskite solar cells renders them attractive for multijunction architectures1. Combinations with silicon and copper indium gallium selenide (CIGS), as well as all-perovskite tandem cells, have been reported2-5. Meanwhile, narrow-gap non-fullerene acceptors have unlocked skyrocketing efficiencies for organic solar cells6,7. Organic and perovskite semiconductors are an attractive combination, sharing similar processing technologies. Currently, perovskite-organic tandems show subpar efficiencies and are limited by the low open-circuit voltage (Voc) of wide-gap perovskite cells8 and losses introduced by the interconnect between the subcells9,10. Here we demonstrate perovskite-organic tandem cells with an efficiency of 24.0 per cent (certified 23.1 per cent) and a high Voc of 2.15 volts. Optimized charge extraction layers afford perovskite subcells with an outstanding combination of high Voc and fill factor. The organic subcells provide a high external quantum efficiency in the near-infrared and, in contrast to paradigmatic concerns about limited photostability of non-fullerene cells11, show an outstanding operational stability if excitons are predominantly generated on the non-fullerene acceptor, which is the case in our tandems. The subcells are connected by an ultrathin (approximately 1.5 nanometres) metal-like indium oxide layer with unprecedented low optical/electrical losses. This work sets a milestone for perovskite-organic tandems, which outperform the best p-i-n perovskite single junctions12 and are on a par with perovskite-CIGS and all-perovskite multijunctions13.

Suppressed decomposition of organometal halide perovskites by impermeable electron-extraction layers in inverted solar cells.

The area of thin-film photovoltaics has been overwhelmed by organometal halide perovskites. Unfortunately, serious stability concerns arise with perovskite solar cells. For example, methyl-ammonium lead iodide is known to decompose in the presence of water and, more severely, even under inert conditions at elevated temperatures. Here, we demonstrate inverted perovskite solar cells, in which the decomposition of the perovskite is significantly mitigated even at elevated temperatures. Specifically, we introduce a bilayered electron-extraction interlayer consisting of aluminium-doped zinc oxide and tin oxide. We evidence tin oxide grown by atomic layer deposition does form an outstandingly dense gas permeation barrier that effectively hinders the ingress of moisture towards the perovskite and-more importantly-it prevents the egress of decomposition products of the perovskite. Thereby, the overall decomposition of the perovskite is significantly suppressed, leading to an outstanding device stability.

A novel label-free cell-based assay technology using biolayer interferometry.

Biolayer interferometry (BLI) is a well-established optical label-free technique to study biomolecular interactions. Here we describe for the first time a cell-based BLI (cBLI) application that allows label-free real-time monitoring of signal transduction in living cells. Human A431 epidermoid carcinoma cells were captured onto collagen-coated biosensors and serum-starved, followed by exposure to agonistic compounds targeting various receptors, while recording the cBLI signal. Stimulation of the epidermal growth factor receptor (EGFR) with EGF, the ß2-adrenoceptor with dopamine, or the hepatocyte growth factor receptor (HGFR/c-MET) with an agonistic antibody resulted in distinct cBLI signal patterns. We show that the mechanism underlying the observed changes in cBLI signal is mediated by rearrangement of the actin cytoskeleton, a process referred to as dynamic mass redistribution (DMR). A panel of ligand-binding blocking and non-blocking anti-EGFR antibodies was used to demonstrate that this novel BLI application can be efficiently used as a label-free cellular assay for compound screening and characterization.

Plasmonically sensitized metal-oxide electron extraction layers for organic solar cells.

ZnO and TiOx are commonly used as electron extraction layers (EELs) in organic solar cells (OSCs). A general phenomenon of OSCs incorporating these metal-oxides is the requirement to illuminate the devices with UV light in order to improve device characteristics. This may cause severe problems if UV to VIS down-conversion is applied or if the UV spectral range (λ < 400 nm) is blocked to achieve an improved device lifetime. In this work, silver nanoparticles (AgNP) are used to plasmonically sensitize metal-oxide based EELs in the vicinity (1-20 nm) of the metal-oxide/organic interface. We evidence that plasmonically sensitized metal-oxide layers facilitate electron extraction and afford well-behaved highly efficient OSCs, even without the typical requirement of UV exposure. It is shown that in the plasmonically sensitized metal-oxides the illumination with visible light lowers the WF due to desorption of previously ionosorbed oxygen, in analogy to the process found in neat metal oxides upon UV exposure, only. As underlying mechanism the transfer of hot holes from the metal to the oxide upon illumination with hν < Eg is verified. The general applicability of this concept to most common metal-oxides (e.g. TiOx and ZnO) in combination with different photoactive organic materials is demonstrated.

Elemental distribution, solute solubility and defect free volume in nanocrystalline restricted-equilibrium Cu-Ag alloys.

In this article we study the elemental distribution and solute solubility in nanocrystalline alloys of immiscible components near restricted equilibrium for the case of the binary Cu-Ag system. As predicted from thermodynamic considerations, a grain boundary segregated monophase alloy is observed in the annealed mechanically alloyed state for low Ag content by using atom probe tomography. From the detected Ag solute grain boundary enrichment the segregation free enthalpy is estimated to range between -25 and -49 kJ mol(-1) following the McLean equation, in agreement with values reported for coarse-grained Cu-Ag. The extension of the alloying range is described by a two-domain thermodynamic model that considers the excess free volume in the grain boundaries and the strain in the grain interior on the basis of the universal equation of state at negative pressure. To access the grain boundary volumetric strain experimentally, a method based on a combination of density measurements and microscopical quantification of closed pore areas is presented. Moreover, we apply x-ray diffraction line broadening analysis to determine the local strain amplitude, which yields a root-mean-square microstrain of ~0.3% for a grain size of ~30 nm. It is shown that the grain boundary free volume represents the major origin for the global solubility enhancement in nanocrystalline Cu-Ag at 503 K.

Water as origin of hysteresis in zinc tin oxide thin-film transistors.

The hysteresis behavior of transparent zinc tin oxide (ZTO) thin film transistors (TFTs) is identified to be a result of short-term bias stress induced by the measurement. The related density of shallow defect states can be adjusted by the amount of water in the ambient. Time-resolved studies of the TFTs under varied ambient demonstrate that hysteresis can be immediately switched on and off by the adsorption and desorption of water, respectively. These findings are expected to be of general importance also for other oxide-based TFTs.

ELNES study of chemical solution deposited SrO(SrTiO(3))(n) Ruddlesden-Popper films: experiment and simulation.

This article analyzes electron energy-loss near-edge fine structures of the SrO(SrTiO(3))(n=1) Ruddlesden-Popper system and of the parent compounds SrTiO(3) and SrO by comparison with first principles calculations. For that, the fine structures of chemical solution deposited Ruddlesden-Popper films have been experimentally recorded by means of transmission electron microscopy. Moreover, density of states computations using an all-electron density-functional code have been performed. It is shown that the appearance and shape of the experimental O-K and Ti-L(2,3) fine structure features result from the crystallography-dependent electronic structure of the investigated oxides, which display technologically interesting dielectric as well as lattice-structural properties.

Highly sensitive determination of the polaron-induced optical absorption of organic charge-transport materials.

We examine polaron-induced absorption in organic transport materials using a highly sensitive measurement technique. A hole only device is embedded into a low-loss TE2 waveguide structure, and the current induced change of the waveguide absorption is measured. The exemplary study of 2,2('),7,7(')-tetrakis(N,N-diphenylamine)-9,9(')-spiro-bifluorene (S-TAD) reveals a very low polaron absorption cross section of sigma(p) < or = 2.6 x 10(-18) cm(2) for 560 nm < or = lambda < or = 660 nm. The accuracy of this data is unsurpassed by other techniques used for the unambiguous study of polaronic species in organic thin films.

Determination of manganese valency in La1-xSrxMnO3 using ELNES in the (S)TEM.

In this article several experimentally identified Mn valence-sensitive ELNES quantities for the La1-xSrxMnO3 compound class are presented, namely the energy separations between Mn-L3 and O-Ka, between O-Kb and O-Ka edges, the Mn-L2,3 white line intensity ratio, and the Mn-L3 line width. Valence sensitivities of these quantities are evaluated, and possible additional influences on them are considered. At high signal-to-noise ratio the two energy separations display most sensitively changes of the Mn valency. An experiment-based estimation of the total uncertainties of the quantities indicates that at low signal-to-noise ratio, which is the case when studying interface effects at high spatial resolution, again both energy separations allow to resolve the smallest valency changes.

Extraction of EELS white-line intensities of manganese compounds: methods, accuracy, and valence sensitivity.

This article evaluates the valence sensitivity and accuracy of selected EELS white-line extraction methods based on the white-line intensity ratio in case of manganese oxides, predominantly in the valency range [Mn3+ ; Mn4+]. For this purpose Mn-L2,3 ionization edges of several Mn oxides were measured and four different methods were applied to extract the intensities. The obtained ratios have been analyzed in terms of their errors, their scatter, and their sensitivity on manganese valency. We found that the maximum-intensity as well as the Pearson and Walsh-Dray methods show larger relative changes of the ratio between Mn3+ and Mn4+ than curve-fitting. Taking the scatter into account, Walsh-Dray distinguishes more clearly between those two valencies than curve-fitting. Thus the Walsh-Dray method promises the most accurate determination of small valency shifts.

[Reliability of fetal pulse oximetry for the detection of fetal acidosis]. / Die Zuverlässigkeit der fetalen Pulsoxymetrie bei der Detektion einer fetalen Azidose.

Fetal pulse oximetry is a continuous method to exclude the lack of oxygen in cases of non-reassuring fetal heart rate. This study aims at the evaluation of the predictive value of this method concerning the development of fetal acidosis. 136 fetuses with non-reassuring heart rate were monitored by fetal pulse oximetry. In all cases fetal blood pH and base excess were determined repeatedly by fetal blood analysis (FBA). The pH value and base excess in the umbilical artery and scalp blood as well as the changes of pH and base excess were correlated to the duration of low, medium and high fetal oxygen saturation (FSpO (2)). Sensitivity, specificity, positive and negative predictive values were calculated for the assumption that "FSpO (2) < or = 30 % for at least 10 or 15 minutes" predicts a pH or base excess in the umbilical artery and in FBA of < 7.1/7.15/7.2 or < or = -4/8/12 mmol/L and a decline of pH (base excess) by more than 0.05 (0.1) pH units (4 mmol/L). A highly significant negative correlation was found between umbilical artery and FBA pH and base excess as well as the change of both and the duration of low oxygen saturation. Additionally the change of FBA pH depends on the duration of medium FSpO (2). A pH below 7.15 in FBA as well as base excess < or = -12 mmol/L were safely detected by a cut-off of "FSpO (2) < or = 30 % for at least 10 minutes" and pH < 7.1 and base excess < or = -12 mmol/l in FBA in 100 % and 75 %, respectively. A decline of pH by more than 0.1 pH units and of base excess by more than 4 mmol/L were excluded by a negative predictive value of 98 %. In conclusion, medium and progressive acidosis can be reliably excluded by fetal pulse oximetry.

Phosphorylation in transcription: the CTD and more.

Phosphorylation appears to be one mechanism in the regulation of transcription. Indeed, a multitude of factors involved in distinct steps of transcription, including RNA polymerase II, the general transcription factors, pre-mRNA processing factors, and transcription activators/repressors are phosphoproteins and serve as substrates for multiple kinases. Among these substrates, most attention has been paid in recent years to the phosphorylation of the carboxyl-terminal domain (CTD) of RNA polymerase II and its role in transcription regulation. Kinases responsible for such CTD phosphorylation that are associated with RNA polymerase II at distinct steps of transcription, such as cdk7 and cdk8, also phosphorylate some other components of the transcription machinery in a regulatory manner. These observations enlighten the pivotal role of such kinases in an entangled regulation of transcription by phosphorylation. Summarizing the phosphorylation of various components of the transcription machinery, we point out the variety of steps in transcription that are regulated by such protein modifications, envisioning an interconnection of the several stages of mRNA synthesis by phosphorylation.

Activation of estrogen receptor alpha by S118 phosphorylation involves a ligand-dependent interaction with TFIIH and participation of CDK7.

Phosphorylation of the estrogen receptor alpha (ERalpha) N-terminal transcription activation function AF1 at serine 118 (S118) modulates its activity. We show here that human ERalpha is phosphorylated by the TFIIH cyclin-dependent kinase in a ligand-dependent manner. Furthermore, the efficient phosphorylation of S118 requires a ligand-regulated interaction of TFIIH with AF2, the activation function located in the ligand binding domain (LBD) of ERalpha. This interaction involves (1) the integrity of helix 12 of the LBD/AF2 and (2) p62 and XPD, two subunits of the core TFIIH. These findings are suggestive of a novel mechanism by which nuclear receptor activity can be regulated by ligand-dependent recruitment of modifying activities, such as kinases.

Oral preanaesthetic medication for children: double-blind randomized study of a combination of midazolam and ketamine vs midazolam or ketamine alone.

Anxiolysis and sedation with oral midazolam are common practice in paediatric anaesthesia. However, good or excellent results are seen in only 50-80% of cases. For this reason, we investigated if addition of a low dose of oral ketamine (MIKE: ketamine 3 mg kg-1, midazolam 0.5 mg kg-1) resulted in better premedication compared with oral midazolam 0.5 mg kg-1 or ketamine 6 mg kg-1 alone, in a prospective, randomized, double-blind study. We studied 120 children (mean age 5.7 (range 2-10) yr) undergoing surgery of more than 30 min duration. After oral premedication in the ward and transfer, the child's condition in the induction room was evaluated by assigning 1-4 points to the quality of anxiolysis, sedation, behaviour at separation from parent and during venepuncture (transfer score). On days 1 and 7 after operation, parents were interviewed for changes in behaviour (eating, sleep, dreams, toilet training), recollection and satisfaction, using a standardized questionnaire. The groups were similar in age, sex, weight, intervention and duration of anaesthesia. The transfer score was significantly better in the MIKE group (12.5 (95% confidence interval (CI) 11.9-13.1)) than in the ketamine or midazolam groups (10.6 (9.8-11.4) and 11.5 (10.7-12.3), respectively). Success rates for anxiolysis and behaviour at separation were greater than 90% with the combination, approximately 70% with midazolam and only 51% with ketamine alone. The incidence of salivation, excitation and psychotic symptoms was low in all groups. Vertigo and emesis before induction were significantly more frequent after ketamine premedication. During recovery, there were no differences in sedation or time of possible discharge. After 1 week, parents reported nightmares (ketamine five, midazolam three, MIKE one), restless sleep (five/four/four) or negative memories (three/four/one). There were no major or continuing disturbances in behaviour or development. In summary, significantly better anxiolysis and separation were observed with a combination of ketamine and midazolam, even in awake children (sedation was not successful according to the preset criteria), than with midazolam or ketamine alone. Duration of action and side effects of the combination were similar to those of midazolam. The combination of both drugs in strawberry flavoured glucose syrup (pH 4.5 approximately) is chemically stable for 8 weeks.

TFIIH interacts with the retinoic acid receptor gamma and phosphorylates its AF-1-activating domain through cdk7.

Retinoic acid receptor gamma (RARgamma) is phosphorylated in COS-1 cells at two conserved serine residues located in the N-terminal region (serines 77 and 79 in RARgamma1 and serines 66 and 68 in RARgamma2) that contains the activation function AF-1. These serines are phosphorylated in vitro by cdk7, a cyclin-dependent kinase associated to cyclin H and MAT1 in the CAK complex (cdk7.cyclin H. MAT1), that is found either free or as a component of the transcription/DNA repair factor TFIIH. RARgamma is more efficiently phosphorylated by TFIIH than by CAK and interacts not only with cdk7 but also with several additional subunits of TFIIH. RARgamma phosphorylation and interaction with TFIIH occur in a ligand-independent manner. Our data demonstrate also that phosphorylation of the AF-1 function modulates RARgamma transcriptional activity in a response gene-dependent manner.

Spatial-frequency bands in complex visual stimuli: American Sign Language.

Dynamic images of individual signs of American Sign Language (ASL) with a resolution of 96 X 64 pixels were bandpass filtered in adjacent frequency bands. Intelligibility was determined by testing deaf subjects fluent in ASL. The following results were obtained. (1) By iteratively varying the center frequencies and bandwidths of the spatial bandpass filters, it was possible to divide the original signal into four different component bands of high intelligibility. (2) The measured temporal-frequency spectrum was approximately the same in all bands. (3) The masking of signals in band i by noise in band j was found to be inversely proportional to log [f signal/f noise]. At constant performance, the ratio of root-mean-square signal amplitude to noise amplitude, s/n, was the same for bands 2,3, and 4 and higher for band 1. (4) When weak signals i and j were added linearly, there was a slight intelligibility advantage for signals in the same band (i = j) compared with signals in adjacent bands and for signals in adjacent bands compared with signals in distant bands.

Limits of visual communication: the effect of signal-to-noise ratio on the intelligibility of American Sign Language.

To determine the limits of human observers' ability to identify visually presented American Sign Language (ASL), the contrast s and the amount of additive noise n in dynamic ASL images were varied independently. Contrast was tested over a 4:1 range; the rms signal-to-noise ratios (s/n) investigated were s/n = 1/4, 1/2, 1, and infinity (which is used to designate the original, uncontaminated images). Fourteen deaf subjects were tested with an intelligibility test composed of 85 isolated ASL signs, each 2-3 sec in length. For these ASL signs (64 x 96 pixels, 30 frames/sec), subjects' performance asymptotes between s/n = 0.5 and 1.0; further increases in s/n do not improve intelligibility. Intelligibility was found to depend only on s/n and not on contrast. A formulation in terms of logistic functions was proposed to derive intelligibility of ASL signs from s/n, sign familiarity, and sign difficulty. Familiarity (ignorance) is represented by additive signal-correlated noise; it represents the likelihood of a subject's knowing a particular ASL sign, and it adds to s/n. Difficulty is represented by a multiplicative difficulty coefficient; it represents the perceptual vulnerability of an ASL sign to noise and it adds to log(s/n).