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Nontraditional architectures and spin processes in organic light emitting devices

Pirkle, Wesley C
http://rave.ohiolink.edu/etdc/view?acc_num=osu1111626474

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Physics.
Controlling spin processes in organic light emitting devices (OLEDs) offers a means of improving device efficiency and manipulating the color of emitted light. Phosphorescent materials have been doped into both small molecule and polymer hosts to allow radiative recombination of triplet excitons. These doped emitting layers have been incorporated into unique architectures including symmetrically configured AC light emitting devices (SCALE), which emit light under both forward and reverse bias as well as AC voltage, and spin OLEDs, which use ferromagnetic electordes in place of the typical electrodes, indium tin oxide (ITO) and aluminum, to alter exciton formation statistics. The device structures were studied using electroluminescense (EL), photoluminescense (PL), UV/VIS/NIR spectroscopy, and magnetic measurements. SCALE devices were found to be degraded when the water based solution of fully sulfonated polyaniline (NSPAN) was applied on top of the emitting layer. The effect of the water was found to be slightly reduced either by increasing the thickness of the emitting layer or by introducing barrier layers that kept the water from coming into direct contact with the emitter. The introduction of the barrier layers also allowed for the development of a color variable device. Spin OLEDs were fabricated using the ferromagnetic electrodes cobalt and iron as charge and spin injectors. A large reduction in device performance was observed compared to traditional ITO/Al devices. Turn on voltages were increased by a factor of four and large leakage currents were present in the device. Possible explanations for this include chemical interactions between the organic layers and the ferromagnets, and iron implantation into the organic layers during thermal deposition of the iron cathode. The insertion of an EB layer between the cobalt anode and emitting layer greatly improved device performance. Upon application of a magnetic field, no changes in the device operating characteristics were found indicating a lack of effects due to spin injection. Oxide layers were inserted in devices using both ITO/Al electrodes and Co/Fe electrodes. No emission was found from devices with the ferromagnetic electodes while emission spectra were shifted from the ITO/Al electrodes.
Arthur Epstein (Advisor)
139 p.
Physics, Condensed Matter
Orgainic light emitting devices; Spin Injection; Phosphorescence

Recommended Citations

Citations

  • Pirkle, W. C. (2005). Nontraditional architectures and spin processes in organic light emitting devices [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1111626474

    APA Style (7th edition)

  • Pirkle, Wesley. Nontraditional architectures and spin processes in organic light emitting devices. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1111626474.

    MLA Style (8th edition)

  • Pirkle, Wesley. "Nontraditional architectures and spin processes in organic light emitting devices." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1111626474

    Chicago Manual of Style (17th edition)

osu1111626474
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© 2005, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.