Solar cells, light emitting diodes, and X-ray detectors based on perovskite materials often incorporate gold electrodes, either in direct or indirect contact with the perovskite compound. Chemical interactions between active layers and contacts deteriorate the operation and induce degradation, being the identification of the chemical nature of such interfacial structures an open question. Chemical reactivity of gold in contact with the perovskite semiconductor leads to reversible formation of oxidized gold halide species and explains the generation of halide vacancies in the vicinity of the interface.Electrical biasing induces contact reaction and produces modifications of the current level by favoring the ability of perovskite/Au interfaces to inject electronic carriers. The current injection increment does not depend on the halogen source used, either extrinsically by iodine vapor sublimation of Au electrodes, or intrinsically by bias-driven migration of bromide ions. In addition, the formation of a dipole-like structure at the reacted electrode that lowers the potential barrier for electronic carriers is confirmed. These findings highlight adequate selection of the external contacts and suggest the need for a deeper understanding of contact reactivity as it dominates the operation characteristics, rather than being governed by the bulk transport properties of the charge carriers, either electronic or ionic.conversion in the near future. In addition to photovoltaic applications, perovskitebased materials are being explored as sensitive layers for high-energy radiation detectors and imaging devices for medical diagnostics. [2] These detection technologies rely upon the ability of perovskite compounds of absorbing high-energy photons and convert their energy into electronic carriers that are finally collected at the outer contacts. For soft X-ray photons (<10 keV), absorbing layer thickness of tens of micrometers suffices to stop the radiation. But hard X-ray radiation (10-50 keV) possesses much longer penetration length (≈100 µm) in compounds as methylammonium lead iodide or bromide (MAPbI 3 and MAPbBr 3 ). [3] Hence, relatively thick layers (0.1-1 mm) need to be employed to achieve sufficient electrical signal. Despite the large electronic carrier mobility and mobility-lifetime product, [4,5] such thick absorbing layers should be externally biased in order to increase the detector responsivity. Electrical fields as high as ≈0.1-1 V µm −1 are commonly needed for poly-crystalline perovskite deposits incorporated into X-ray detectors. [3,5] Large field strength requirements are in some amount lowered when devising single-crystal approaches for X-ray detection using perovskite materials. [4,6] In any case, it is widely recognized that the application of an external bias promotes the displacement and interfacial built-up of intrinsic mobile ions. [7,8] Ion accumulation finally shields the electrical field within the absorbing layer bulk, reducing as a consequence the detector sensitivity. The applicability of perovs...

Temperature-modulated space-charge-limited-current spectroscopy (TMSCLC) is applied to quantitatively evaluate the density of trap states in the band-gap with high energy resolution of semiconducting hybrid lead halide perovskite single crystals. Interestingly multicomponent deep trap states were observed in the pure perovskite crystals, which assumingly caused by the formation of nanodomains due to the presence of the mobile species in the perovskites.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractThe conductivity of DNA covalently bonded to a gold surface was studied by means of the STM technique. Various single-and double-stranded 32-nucleotide-long DNA sequences were measured under ambient conditions so as to provide a better understanding of the complex process of chargecarrier transport in natural as well as chemically modified DNA molecules. The investigations focused on the role of several features of DNA structure, namely the role of the negative charge at the backbone phosphate group and the related complex effects of counterions, and of the stacking interactions between the bases in Watson-Crick and other types of base pairs. The measurements have indicated that the best conductor is DNA in its biologically most relevant double-stranded form with Watson-Crick base pairs and charged phosphates equilibrated with counterions and water. All the studied modifications, including DNA with non-Watson-Crick base pairs, the abasic form, and especially the form with phosphate charges eliminated by chemical modifications, lower the conductivity of natural DNA.

Versatile approaches to nanoparticle synthesis offer unprecedented opportunities for the development of optoelectronics, photonics, as well as bio sciences. With the current advancement of hybrid organic-inorganic metal halide perovskites, the next step is to expand their field of applications via utilization of functional and modifiable ligand chemistry. Here, we present a ligand assisted reprecipitation approach for highly luminescent perovskite nanoparticle synthesis using for the first time L-lysine and L-arginine for surface passivation. These nanoparticles exhibit emission within a narrow bandwidth of the visible spectrum and photoluminescence quantum yield close to 100%. Additionally, preferential ligand orientation is achieved via amino acids α-amino group blocking which results in blueshifted emission as well as smaller and more uniform particle size. These experimental results demonstrate the effectiveness of naturally occurring proteinogenic amino acids as surface ligands and offer possibilities for versatile modification of perovskite nanoparticle properties via well-studied amino acid chemistry.

Biocompatibility tests and a study of the electrical properties of thin films prepared from six electroactive polymer ink formulations based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were performed. The aim was to find a suitable formulation of PEDOT:PSS and conditions for preparing thin films in order to construct printed bioelectronic devices for biomedical applications. The stability and electrical properties of such films were tested on organic electrochemical transistor (OECT)-based sensor platforms and their biocompatibility was evaluated in assays with 3T3 fibroblasts and murine cardiomyocytes. It was found that the thin films prepared from inks without an additive or any thin film post-treatment provide limited conductivity and stability for use in biomedical applications. These properties were greatly improved by using ethylene glycol and thermal annealing. Addition or post-treatment by ethylene glycol in combination with thermal annealing provided thin films with electrical resistance and a stability sufficient to be used in sensing of animal cell physiology. These films coated with collagen IV showed good biocompatibility in the assay with 3T3 fibroblasts when compared to standard cell culture plastics. Selected films were then used in assays with murine cardiomyocytes. We observed that these cells were able to attach to the PEDOT:PSS films and form an active sensor element. Spontaneously beating clusters were formed, indicating a good physiological status for the cardiomyocyte cells. These results open the door to construction of cheap printed electronic devices for biointerfacing in biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1121-1128, 2018.