Transparent manganite films as hole injectors for organic light emitting diodes

• Published in: Journal of luminescence Vol. 110; no. 4; pp. 384 - 388
• Main Authors: Bergenti, I., Dediu, V., Murgia, M., Riminucci, A., Ruani, G., Taliani, C.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2004; Elsevier
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronics; Exact sciences and technology; Light-emitting diodes; Magnetic properties and materials; Magnetotransport phenomena, materials for magnetotransport; Manganites; Optoelectronic devices; Organic semiconductors; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Spin injection; Thin films; Thin films; 78.66.Sq; 85.60.Jb; 72.25.Ba; 75.47.Lx; Organic semiconductors; Light-emitting diodes; Spin injection; Manganites; 72.80.Le; 85.60.Jb Light-emitting diodes; Exciton; Doping; Fluorescence; Electroluminescence; Lanthanide compound; Triplet state; Strontium Manganites; Spin orbit interaction; Lanthanum Manganites; Transition element compounds; Spin polarization; Singlet state; Colossal magnetoresistance; Light emitting diode; Quaternary compound; Excited state; Charge carrier injection
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/j.jlumin.2004.08.036

Organic light-emitting diodes (OLEDs) are nowadays one of the most attractive devices based on organic semiconductors due to their successful application in the display technology. Electroluminescence in OLEDs is mainly governed by the fluorescence from excited singlet states, which have large transition probabilities providing the major radiative pathway. The “forbidden” triplet state emission can be activated by increasing spin–orbit coupling via dye doping. The singlet–triplet exciton formation statistics is usually given by 1:3 partition due to the quantum constrains. Injection of carriers with finite spin polarisation should influence and modify the recombination statistics and can be used for tuning of the device efficiency. In this context, the development of a new class of electrodes able to guarantee both efficient charge and spin injection becomes of paramount importance. We show that strongly spin polarised colossal magnetoresistance manganite La 0.7Sr 0.3MnO 3 (LSMO) can successfully substitute conventional ITO electrodes in OLEDs. Highly transparent, metallic and ferromagnetic LSMO layers were used in combination with standard Al and spin polarised Co top electrodes. Electrical and optical characterisations of the OLEDs with spin polarised electrodes indicate the applicability of the new manganite electrodes for organic light-emitting devices.