From Event: SPIE Organic Photonics + Electronics, 2016
In modern electronic systems memory elements are of fundamental importance for data storage. Especially solution-processable nonvolatile organic memories, which are inexpensive and can be manufactured on flexible substrates, are a promising alternative to brittle inorganic devices. Organic photochromic switchable compounds, mostly dithienylethenes (DTEs), are thermally stable, fatigue resistant and can undergo an electrically- or/and photo-induced ring-opening and -closing reaction which results in a change of energy levels. Due to the energetic difference in the highest occupied molecular orbital (HOMO) between the open and closed isomer, the DTE layer can be exploited as a switchable hole injection barrier that controls the electrical current in the diode. We demonstrated that a light-emitting organic memory (LE-OMEM) device with a perfluoro DTE transduction layer can be switched electrically via high current densities pulses and optically by irradiated light, with impressive current ON/OFF Ratios (OOR) of 10Λ2, 10Λ4 respectively.
Currently we aim to minimize the barrier of the ON state and maximize the barrier of the OFF state by designing DTE molecules with larger differences in the HOMO energies of the two isomers yielding improved OOR values. By synthesizing perhydro derivates of DTE we achieved molecules with high HOMO levels and large ΔHOMO energies providing OMEM devices with excellent physical properties (OOR 1.4 x higher than perfluoro DTE). Due to the high HOMO level of the perhydro DTE utilization of hole transport layers (HTLs) is not necessary and thus manufacturing of OMEM devices is simplified.
Sandra Cordes, Darius Kranz, Eduard Maibach, Maxim Kempf, and Klaus Meerholz, "Enhanced organic memory devices (OMEM) with a photochromic perhydro DTE as a transduction layer
(Conference Presentation)," Proc. SPIE 9939, Light Manipulating Organic Materials and Devices III, 99390M (Presented at SPIE Organic Photonics + Electronics: September 01, 2016; Published: 3 November 2016); https://doi.org/10.1117/12.2236297.5167077731001.
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