Organic luminescent devices and magnetoelectronics

Abstract

Developments in magnetoelectronics are advancing by combination of once disparate areas of research in magnetic materials, semiconductor electronics, and optoelectronics. We explore the integration of magnetic materials with organic semiconductors. Because small spin–orbit coupling in these materials minimizes spin relaxation, they may be useful in spintronic applications. Motivated by a theoretical investigation into spin-dependent exciton formation that predicts a magnetoluminescence valve effect, we attempt to manipulate spin-polarized holes and electrons in an effort to generate magnetic field dependent luminescence in organic light emitting diodes (OLEDs). We have fabricated various functional OLEDs consisting of ferromagnetic electrodes sandwiching a organic semiconducting bilayer, thus demonstrating that hole and electron injection from magnetic electrodes is possible. However, magnetic transition metal anodes produce higher turn-on voltages and significantly reduced lifetimes compared to indium–tin–oxide based OLED’s.

Large magnetoresistance in nonmagneticπ-conjugated semiconductor thin film devices

“…However, even when running the device at a constant current, a small but non-zero MFE remains that may be attributable to an MFE on the emission efficiency of the device. Here we note that all the prior work on MFE [7,11,12,13] we know of assumed that the magnetic field affects the emission efficiency directly, whereas the MR effect was largely neglected. Fig.…”

“…Recently there has been a growing interest in spin [4,5,6] and magnetic field effects [7,8,9,10,11,12,13,14] in these materials. During the study of sandwich devices made from the π-conjugated polymer polyfluorene (PFO) we recently discovered a large and intriguing magnetoresistive (MR) effect, which we dubbed organic magnetoresitance (OMAR).…”

Morphology and electronic properties of the pentacene on cobalt interface

“…Applications into electronic devices in which the spin degree of freedom of the electron is exploited ͑spintronics͒ have recently started to be considered, motivated by the notion that organic semiconductors are materials with large spin relaxation times. [1][2][3][4][5] Spin valves with a significant magnetoresistance have been produced with Alq 3 thin films sandwiched between two ferromagnetic electrodes. 4,5 In response to the technological success of the organic semiconductors, fundamental research, with the goal of understanding the surface and interface properties of these systems, has followed.…”

Observation of a large spin-dependent transport length in organic spin valves at room temperature

“…Most importantly, a large SDT length of approximately 110 nm was experimentally observed in the C 60 layer at room temperature. This research may strongly motivate the development of spin-based organic devices, such as organic spin valves [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and spin-based organic light-emitting diodes 20 .…”