A metal-free cathode for organic semiconductor devices

Abstract

We introduce a class of low-reflectivity, high-transparency, nonmetallic cathodes useful for a wide range of electrically active, transparent organic devices. The metal-free cathode employs a thin film of copper phthalocyanine (CuPc) capped with a film of low-power, radio-frequency sputtered indium tin oxide (ITO). The CuPc prevents damage to the underlying organic layers during the ITO sputtering process. We present a model suggesting that damage-induced states at the cathode/organic film interface are responsible for the electron injection properties of the contact. Due to the low contact reflectivity, a non-antireflection-coated, metal-free transparent organic light-emitting device (MF-TOLED) is demonstrated with 85% transmission in the visible, emitting nearly identical amounts of light in the forward and backscattered directions. The MF-TOLED performance is found to be comparable to that of conventional TOLEDs employing a more reflective and absorptive cathode consisting of a semitransparent thin film of Mg:Ag capped with ITO.

Voltage-Induced Switching Dynamics of a Coupled Spin Pair in a Molecular Junction

“…Arrays of magnetic molecules inserted between conducting leads, moreover, provide an important forum to investigate fundamental magnetic properties of finite one-dimensional Ising or Heisenberg chains [14][15][16] as well as potential for electrical and thermal control of the magnetic state. Certain classes of molecules, e.g., metal-phthalocyanines (MPc) and metal-porhyrins (MP) present chemical stability with specific optical and electrical properties make them highly appreciated for technological applications including organic field effect transistors [17,18], light emitting devices [19,20] and photovoltaic cells [21], and for fundamental studies [7,[22][23][24][25][26][27].While incorporation of magnetic elements in molecular compounds can have a significant effect on the overall molecular transport properties [7], the main established route to spintronics manipulations entails external magnetic fields [2] or ferromagnetic electrodes [28,29], often exploiting spin transfer torques from spin-polarized scattering [30] or Coulomb interaction [31]. Here, we propose a different route to molecular spintronics based on voltage induced control of magnetic interactions that allows for all electrical control of the transport properties.…”

“…Arrays of magnetic molecules inserted between conducting leads, moreover, provide an important forum to investigate fundamental magnetic properties of finite one-dimensional Ising or Heisenberg chains [14][15][16] as well as potential for electrical and thermal control of the magnetic state. Certain classes of molecules, e.g., metal-phthalocyanines (MPc) and metal-porhyrins (MP) present chemical stability with specific optical and electrical properties make them highly appreciated for technological applications including organic field effect transistors [17,18], light emitting devices [19,20] and photovoltaic cells [21], and for fundamental studies [7,[22][23][24][25][26][27].…”

Coupled surface plasmon-polariton mediated photoluminescencefrom a top-emitting organic light-emitting structure

“…Our results show that the addition of a dielectric grating to otherwise planar structures, such as surface-emitting organic light-emitting diodes, may offer a way to increase the external efficiency of top-emitting organic light-emitting diodes. Top-emitting organic light-emitting diodes (OLEDs) [1][2][3] have two advantages over substrate-emitting structures. First, the drive electronics may be integrated into an opaque silicon substrate and second, losses associated with guided modes in the substrate are eliminated.…”

Charge Transport and Entropy Production Rate in Magnetically Active Molecular Dimer

“…Notice that while the exchange interaction is defined in terms of the two-electron propagator (−i) Ts(t)s(t ) [53], we employ the de-coupling approximation (−i)spσG 12 (t, t )σG 21 (t , t). Here, G mn (t, t ) is a singleelectron Green function for the molecular orbitals projected onto the sites m and n, whereas sp defines the trace over spin 1/2 space.…”

“…By this discovery polyacetylene became the test bench, bridging the gap between organic and inorganic chemistry regarding electronic transport [11][12][13]. Since then, charge transport has been extensively studied theoretically and experimentally in molecular junctions [15][16][17][18][19][20][21][22][23][24][25]. From the same standpoint, thermal transport studies were conceived and came to be conclusive in the upcoming years [2].…”