Heinrich Christoph Neitzert

Radiation Hardness and Self‐Healing of Perovskite Solar Cells

The radiation hardness of CH3 NH3 PbI3 -based solar cells is evaluated from in situ measurements during high-energy proton irradiation. These organic-inorganic perovskites exhibit radiation hardness and withstand proton doses that exceed the damage threshold of crystalline silicon by almost 3 orders of magnitude. Moreover, after termination of the proton irradiation, a self-healing process of the solar cells commences.

A noise model for the evaluation of defect states in solar cells

A theoretical model, combining trapping/detrapping and recombination mechanisms, is formulated to explain the origin of random current fluctuations in silicon-based solar cells. In this framework, the comparison between dark and photo-induced noise allows the determination of important electronic parameters of the defect states. A detailed analysis of the electric noise, at different temperatures and for different illumination levels, is reported for crystalline silicon-based solar cells, in the pristine form and after artificial degradation with high energy protons. The evolution of the dominating defect properties is studied through noise spectroscopy.

Differences between graphene and graphene oxide in gelatin based systems for transient biodegradable energy storage applications

A comparison between graphene flakes and graphene oxide as filler in gelatin based systems for low-cost transient biodegradable energy storage applications has been carried out. The two bio-composites have been prepared and characterized by rheological measurements, cyclic voltammetry measurements, chronopotentiometry measurements and impedance spectroscopy. Differences in dielectric and mechanical properties have been correlated to the different structural organizations determinate by the hydrophobic/hydrophilic character of the used filler. In particular, the addition of the graphene oxide to the gelatin causes an increase in the elastic modulus with a parallel increase in the mechanical stability with time as compared to the composites obtained by adding graphene. Conversely, the surface capacitance is slightly increased by the graphene oxide addition compared to the pure gelatin sample. On the other hand, the introduction of the graphene flakes into the gelatin leads to a marked increase of the dielectric properties of the resulting bio-composite.

Photovoltaic Behavior of V 2 O 5 /4H-SiC Schottky Diodes for Cryogenic Applications

The photovoltaic behavior of (divanadioum pentoxide)/(4H polytype silicon carbide) Schottky diodes under ultraviolet illumination and down to 28K is investigated. In addition to their high stability, by using the thermionic model the analysis allows to confirm the predictability of performances at cryogenic temperatures, such as the high light/dark current ratio and the dependence of the photocurrent and open circuit voltage on material parameters. Because of the low-annealing temperature, this structure is shown to be a good candidate for solar-blind photodetectors in the UV spectral range of spatial and terrestrial cryogenic applications.

Blue emitting OLED with oxadiazole/carbazole containing active layer

The optoelectronic properties of a new type of organic light-emitting diode have been measured, which incorporates in the active layer a molecule containing as well an electron conducting and blue emitting oxadiazole group and a hole conducting carbazole group. The investigated device consists of this active oxadiazole/carbazole layer deposited by spin-coating on transparent conductive oxide (TCO) covered glass substrate and top aluminium contacts for electron injection. We compared two types of devices, with and without the insertion of a 40nm thick spin-coated PEDOT layer as hole injector between the active and the TCO layer. Stable blue emission has been observed only for the device with inserted PEDOT layer with an inset of the light emission at an applied voltage of 10V. For devices without PEDOT layer a much higher threshold voltage for light emission and a lower quantum efficiency as compared to the device with intermediate PEDOT layer has been found.

Preliminary investigation of polystyrene/MoS2-Oleylamine polymer composite for potential application as low-dielectric material in microelectronics

Insulating materials play a vital role in the design and performance of electrical systems for both steady and transient state conditions. Among the other properties, also in this field, polymer nanocomposites promise to offer exciting improvements. Many studies in the last decade has witnessed significant developments in the area of nano-dielectric materials and significant effects of nano-scale fillers on electric, thermal and mechanical properties of polymeric materials have been observed. However, the developments of new and advanced materials to be used the miniaturization of electronic devices fabrication require extensive studies on electrical insulation characteristics of these materials before they can be used in commercial systems. In this work, Polystyrene (PS) composites were prepared by the blend solution method using MoS2@Oleylamine nanosheets as filler. The dielectric properties of the resulting comoposite have been investigated at 300K and in the frequency range between 1000 Hz and 1 MHz. ...

Electrical Hole Transport Properties of an Ambipolar Organic Compound With Zn-Atoms on a Crystalline Silicon Heterostructure

In this paper, we investigate the electrical hole transport properties of an organic/inorganic heterostructure consisting of a thin organic film, that combines hole and electron conducting molecules around a bridging Zn-atom, deposited on top of an n-type crystalline silicon substrate. Current-voltage characteristics and capacitance voltage measurements have been used for the determination of the organic layer dielectric and hole conduction parameters.

Electrical Characterization and Modeling of a Gelatin/Graphene System

A gelatin/graphene composite has been analyzed by means of current density-voltage and the electrical impedance measurements. The DC electrical behavior has been interpreted in terms of an equivalent Thevenin model taking into account the open circuit voltage and the series resistance. A model based on the effect of the electrical double layer and on the diffusion of the charge carriers is used for the analysis of the experimental data, obtained in the frequency domain. The model reveals for any applied voltages a marked diffusion process at low frequencies. In particular, where the charge transfer mechanism is dominant, the time distribution of the reaction rates reveals that several multiple step reactions occur in the materials, especially at high values of the applied forward bias voltages.

Sensitive photoreceiver based on carbon nanotube/tobacco cell composite material

A new type of tissue, based on the combination of tobacco cells and multi-walled carbon nanotubes exhibited good mechanical stability even after more than 2 years of room temperature storage. The original intermediate value of electrical conductivity in coplanar configuration, decreased strongly after high electric field stress before the storage period. In the visible wavelength range optical transmission values between 0.1% and 1% have been measured for the more than 100 μm thick sample. The bio/nano-composite in the low-conductivity state revealed to be a sensitive photoreceiver in the visible wavelength range, when illuminated with white LED light. A notable decrease of the low-frequency current noise amplitude with LED illumination has been observed.