Nir Tessler

Bio: Nir Tessler is an academic researcher from Technion – Israel Institute of Technology. The author has contributed to research in topics: Field-effect transistor & Semiconductor laser theory. The author has an hindex of 46, co-authored 235 publications receiving 12728 citations. Previous affiliations of Nir Tessler include University of Cambridge.

Integrated Optoelectronic Devices Based on Conjugated Polymers

Abstract: An all-polymer semiconductor integrated device is demonstrated with a high-mobility conjugated polymer field-effect transistor (FET) driving a polymer light-emitting diode (LED) of similar size. The FET uses regioregular poly(hexylthiophene). Its performance approaches that of inorganic amorphous silicon FETs, with field-effect mobilities of 0.05 to 0.1 square centimeters per volt second and ON-OFF current ratios of >10 6 . The high mobility is attributed to the formation of extended polaron states as a result of local self-organization, in contrast to the variable-range hopping of self-localized polarons found in more disordered polymers. The FET-LED device represents a step toward all-polymer optoelectronic integrated circuits such as active-matrix polymer LED displays.

Efficient near-infrared polymer nanocrystal light-emitting diodes.

Abstract: Conjugated polymers and indium arsenide–based nanocrystals were used to create near-infrared plastic light-emitting diodes. Emission was tunable from 1 to 1.3 micrometers—a range that effectively covers the short-wavelength telecommunications band—by means of the quantum confinement effects in the nanocrystals. The external efficiency value (photons out divided by electrons in) is ∼0.5% (that is, >1% internal) and is mainly limited by device architecture. The near-infrared emission did not overlap the charge-induced absorption bands of the polymer.

Lasing from Conjugated-Polymer Microcavities

Abstract: FOLLOWING the discovery1 of electroluminescence in poly(p-phenylenevinylene) (PPV), considerable effort has been directed towards the realization of optoelectronic devices based on semiconducting conjugated polymers of this type2–6. But the viability of these materials for such applications depends critically on the nature of the photoexcited states—in particular, whether they are predominantly non-emitting interchain species7–9 or emitting intrachain species10. One way to study this fundamental issue is in a device structure known as a microcavity11, which offers the possibility of using quantum electrodynamic effects to alter (and hence probe the nature of) spontaneous and stimulated emission in these materials12–17. Here we make use of such a structure to demonstrate optically driven laser activity in devices based on solid films of PPV. This demonstration of lasing provides direct support for a model10 in which the main photoexcitation in PPV is an emissive intrachain species, and opens the possibility of electrically driven polymer-based lasers.

Charge Transport in Disordered Organic Materials and Its Relevance to Thin‐Film Devices: A Tutorial Review

Abstract: Semiconducting polymers and small molecules form an extremely flexible class of amorphous materials that can be used in a wide range of applications, some of which are display, radio-frequency tags, and solar cells. The rapid progress towards functional devices is occurring despite the lack of sufficient understanding of the physical processes and very little experience in device engineering. This tutorial review aims to provide sufficient intuitive background to draw more researchers to look into the fundamental aspects of device physics and engineering.

Lasers Based on Semiconducting Organic Materials

Abstract: The semiconductor laser is the cornerstone of modern technology and science. It is being incorporated into an increasing number of applications, ranging from element detection through telecommunications to entertainment. This wide spread of applications is due to the spectral range of the semiconductor laser, which extends from the blue to the far IR, and the attainable output power of several tens of watts. Since light-emitting organic materials are also semiconductors, it is an obvious step to try to introduce their inherent advantages into the laser field. While the direct benefits of incorporating organic lasers into applications are very stimulating, the process of making a laser can also teach us much about its constituent material properties. Since organic materials are constantly evolving, the making of lasers incorporates valuable contributions from a variety of disciplines, extending from organic chemistry through physics to device engineering. With this in mind, this review is also intended for those not necessarily familiar with lasers. The rest of the article is organized as follows: A start is made by looking at the definition of a laser and discussing the issues associated with determining its threshold. A historical overview is then given, spanning from the 1960s to the 1990s. Section 5.1 reviews the recent progress in optically pumped lasers and Section 5.2 is devoted to electrical properties of light-emitting diodes (LEDs), which may affect the performance of future electrically pumped lasers. The figures used in this work are largely taken from data acquired by the author and his colleagues. However, the rapid progress in this field is due to a large number of research groups, as the text will show.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Conjugated polymer-based organic solar cells

Abstract: The need to develop inexpensive renewable energy sources stimulates scientific research for efficient, low-cost photovoltaic devices.1 The organic, polymer-based photovoltaic elements have introduced at least the potential of obtaining cheap and easy methods to produce energy from light.2 The possibility of chemically manipulating the material properties of polymers (plastics) combined with a variety of easy and cheap processing techniques has made polymer-based materials present in almost every aspect of modern society.3 Organic semiconductors have several advantages: (a) lowcost synthesis, and (b) easy manufacture of thin film devices by vacuum evaporation/sublimation or solution cast or printing technologies. Furthermore, organic semiconductor thin films may show high absorption coefficients4 exceeding 105 cm-1, which makes them good chromophores for optoelectronic applications. The electronic band gap of organic semiconductors can be engineered by chemical synthesis for simple color changing of light emitting diodes (LEDs).5 Charge carrier mobilities as high as 10 cm2/V‚s6 made them competitive with amorphous silicon.7 This review is organized as follows. In the first part, we will give a general introduction to the materials, production techniques, working principles, critical parameters, and stability of the organic solar cells. In the second part, we will focus on conjugated polymer/fullerene bulk heterojunction solar cells, mainly on polyphenylenevinylene (PPV) derivatives/(1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61) (PCBM) fullerene derivatives and poly(3-hexylthiophene) (P3HT)/PCBM systems. In the third part, we will discuss the alternative approaches such as polymer/polymer solar cells and organic/inorganic hybrid solar cells. In the fourth part, we will suggest possible routes for further improvements and finish with some conclusions. The different papers mentioned in the text have been chosen for didactical purposes and cannot reflect the chronology of the research field nor have a claim of completeness. The further interested reader is referred to the vast amount of quality papers published in this field during the past decade.

Electroluminescence in conjugated polymers

Abstract: Research in the use of organic polymers as the active semiconductors in light-emitting diodes has advanced rapidly, and prototype devices now meet realistic specifications for applications. These achievements have provided insight into many aspects of the background science, from design and synthesis of materials, through materials fabrication issues, to the semiconductor physics of these polymers.

Hybrid Nanorod-Polymer Solar Cells

Abstract: We demonstrate that semiconductor nanorods can be used to fabricate readily processed and efficient hybrid solar cells together with polymers. By controlling nanorod length, we can change the distance on which electrons are transported directly through the thin film device. Tuning the band gap by altering the nanorod radius enabled us to optimize the overlap between the absorption spectrum of the cell and the solar emission spectrum. A photovoltaic device consisting of 7-nanometer by 60-nanometer CdSe nanorods and the conjugated polymer poly-3(hexylthiophene) was assembled from solution with an external quantum efficiency of over 54% and a monochromatic power conversion efficiency of 6.9% under 0.1 milliwatt per square centimeter illumination at 515 nanometers. Under Air Mass (A.M.) 1.5 Global solar conditions, we obtained a power conversion efficiency of 1.7%.

Organic Thin Film Transistors for Large Area Electronics

Abstract: Organic thin-film transistors (OTFTs) have lived to see great improvements in recent years. This review presents new insight into conduction mechanisms and performance characteristics, as well as opportunities for modeling properties of OTFTs. The shifted focus in research from novel chemical structures to fabrication technologies that optimize morphology and structural order is underscored by chapters on vacuum-deposited and solution-processed organic semiconducting films. Finally, progress in the growing field of the n-type OTFTs is discussed in ample detail. The Figure, showing a pentacene film edge on SiO2, illustrates the morphology issue.