HELIOS

High Efficiency LIght-emitters with Organic Spintronics

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 Obiettivo del progetto (Objective)

'Organic semiconductors (OS) are organic materials with semiconductor properties. They are expected to change the electronics as we conceive it at the moment. OS allow producing flexible, large-area and low-cost devices and they are currently used in displays in mobile phones, MP3 players, digital cameras, radios, etc.

Spintronics (“spin-based electronics”) is a new electronics paradigm that deals with the use of the spin of the electrons to produce devices and is expected to provide major breakthroughs in electronics. OS are particularly interesting for spintronics due to the long spin lifetimes theoretically predicted and recently experimentally measured. Only a little is known about the charge transport and even less about spin transport in these materials. Basic properties such as the spin coherence length and time still remain unknown in most of the OS. Research to understand the physical effects involved in OS spintronics is imperative in order to achieve commercially viable devices.

The aim of this project is to investigate the intrinsic spin transport properties in OS and to take advantage of it to improve power consumption in light emission devices. We will investigate how the molecular order, charge conductivity and spin transport properties are correlated, and how these properties affect the light emission efficiency in order to reduce power in light emitting devices.

We will use pentacene among other reasons because it shows polymorphic nature.

The outgoing host is the Massachusetts Institute of Technology – MIT (USA), one of the world references in spintronics. The applicant will learn the most advanced technology in the fabrication and characterization. It will allow him to reintegrate at NanoGune (Spain) in a mature and independent position. Besides increasing his employment opportunities in university or industry, this award will contribute to further development of this area of research and related industry in Europe.'

Introduzione (Teaser)

EU-funded scientists took an important step toward a new generation of light-emitting diodes (LEDs) by investigating injection of spin-polarised currents into organic semiconductors.

Descrizione progetto (Article)

Combination of ferromagnetic metals and molecular materials has opened the way to designing new devices with novel functionalities. Known as organic spintronics, this emerging field has attracted a great deal of attention over the last years. Organic-based spintronic devices such as spin valves are particularly interesting as they take advantage of the long spin lifetime of the organic semiconductors. However, little is known about charge and spin transport in these materials.

The EU-funded project 'High-efficiency light-emitters with organic spintronics' (HELIOS) focused on efficiently injecting spin-polarised currents into organic semiconductor layers to ultimately improve power consumption in LEDs. Scientists investigated how the molecular order, charge conductivity and spin transport properties are correlated, and how these properties affect light-emission efficiency.

Project members initially studied the pentacene organic compound due to its polymorphic nature. However, they turned to other organic semiconductors such as anthracene, copper phthalocyanine and rubrene, as pentacene reacts with oxygen very easily.

Project work was geared into spin injection at the interface of ferromagnetic and organic interfaces and on thin films. Scientists investigated how layers of lithium fluoride can modify the spin of electrons transported through spin valves. Results demonstrated that spin orientation in organic spin valves and inorganic magnetic tunnel junctions can be tuned by changing the deposition order of the different layers.

Scientists succeeded in optimising a lithography method based on fluorinated chemicals to produce transistors on top of organic thin films or single crystals. These transistors combined better characteristics (reduced channel lengths and gate voltage thresholds) compared to other organic devices produced by other lithography techniques. This was due to the clean interface between organic and metal materials. Nevertheless, scientists were unable to further reduce the channel length to observe spin injection.

Work within HELIOS represents a key enabling step for developing devices based on organic semiconductor spintronics. Project findings should lead to major breakthroughs in electronics.