For efficient charge separation and charge transport in optoelectronic materials,small internal reorganization energies are desired. While many p-type organicsemiconductors have been reported with low internal reorganization energies, fewn-type materials with low reorganization energy are known. Metal phthalocyanineshave long received extensive research attention in the field of organic deviceelectronics due to their highly tunable electronic properties throughmodification of the molecular periphery. In this study, density functionaltheory (DFT) calculations are performed on a series of zinc-phthalocyanines(ZnPc) with various degrees of peripheral per-fluoroalkyl(-C3F7) modification. Introduction of the highly electronwithdrawing groups on the periphery leads to a lowering in the energy of themolecular frontier orbitals as well as an increase in the electron affinity.Additionally, all molecules studies are found to be most stable in their anionicform, demonstrating their potential as n-type materials. However, the calculatedinternal reorganization energy slightly increases as a function of peripheralmodification. By varying the degree of modification we develop a strategy forobtaining an optimal balance between low reorganization energy and high electronaffinity for the development of novel n-type optoelectronic materials.

Boron sub-2,3-naphthalocyanine chloride (SubNc) was investigated as a potentialred-sensitive organic photoconductive film (OPF). A photoconductive cell wasfabricated, and its current–voltage characteristics, both with andwithout light irradiation, and external quantum efficiency (EQE) weredetermined. The structure of the photoconductive cell was as follows, withthicknesses in nm given in parentheses: glasssubstrate/In–Zn–O (100)/spiro-2CBP (30)/SubNc(50)/Alq3 (30)/Al (50) (spiro-2CBP =2,7-bis(carbazol-9-yl)-9,9-spirobifluorene; Alq3 =tris(8-hydroxyquinolinato)aluminum). The spiro-2CBP and Alq3 layerswere inserted between the SubNc layer and the electrodes to block dark currentinjection. The three organic layers were successively deposited by evaporationin a vacuum on the In–Zn–O-patterned substrate. SubNc filmabsorbed light in the red region well, with an absorption peak at 695 nm. TheEQE of the cell reached 80% when the applied bias was 15 V. In addition, theblocking layers effectively suppressed dark current in the OPF, whichcorresponded to a current density of 20 nA/cm2 at 15 V. These resultsindicate that SubNc is a promising candidate as a red-sensitive OPF.

Thin films of organic semiconductor PEDOT:PSS deposited onto silicon and fusedsilica substrates. These films were then treated with sulfuric acid(H2SO4) for various amounts of time (i.e., 10, 20, 40,60, and 80 minutes). Preliminary results obtained with FT-IR, UV-VIS, and VanDerPauw conductivity methods suggest that the H2SO4removes the PSS isonomer from the PEDOT:PSS system. This PSS removal alsoinduces a decrease in film thickness.

This paper presents a comparative study on the effects of plasma type and duration on the contact angle of silicon (Si) and fused silica (FS) for the deposition of Poly (3,4 ethyldioxythiophene) Polystyrene Sulfonate (PEDOT:PSS) via drop casting. The two methods used to measure contact angles were goniometry and profilometry. Both methods agreed that the lowest contact angles were given by: 1) 30 seconds in nitrogen/oxygen mix for Si substrates, and 2) 10 minutes in pure oxygen plasma for FS substrates.

We demonstrate Ag-free transparent OLED (TOLED) fabricated by organic vapor phasedeposition (OVPD) using thin Au contacts. Three types of TOLED devices have beenstudied. The first one has been deposited on ITO substrates to compare thin Agand Au films as top cathodes. A 6-fold increase in operational lifetime(LT50, 4 mA/cm2) from 27 h to 172 h can be observedwhen replacing Ag by Au while maintaining similar electro-opticalcharacteristics. Furthermore, a second type of TOLED on thin Au films, replacingITO and suppressing laterally guided modes [1], has been studied. TOLED on ITOsubstrates and on thin Au films exhibit very low onset voltages of 2.2 V. Bothtypes show about 30% transparency in the VIS light region and emit orange lightwith a peak wavelength of 608 nm from either side with a total EQE of about 9%(measured at 1000 cd/m2 in sum). The third type of TOLED wasfabricated with an inverted structure, with the aim to further increaseoperational lifetime by burying the reactive LiF/Al electron injection layer(EIL). This will make the EIL less accessible for oxygen and moisture. Ourresults show difficulties in electron injection when depositing the organicstack on Al/LiF, which may be attributed to an insufficient thermal activationof the EIL.

Ferromagnetic (FM) electrodes chemically anchored with thiol functionalizedmolecules can yield novel molecular spintronics devices (MSDs). However,significant challenges lie in developing commercially viable MSD fabricationapproach utilizing FM electrodes. A practical MSD fabrication approach shouldconsider FM electrodes’ susceptibility to oxidation, chemicaletching, and stress induced deformations during fabrication and usage. Thispaper will discuss NiFe, an alloy used in the present day memory devices andhigh-temperature engineering applications, as a candidate for FM electrode andfor the fabrication of MSDs. Our spectroscopic reflectance studies show thatNiFe starts oxidizing aggressively beyond ∼90 ⁰C. The NiFesurfaces, aged for several months or heated for several minutes below∼90 ⁰C, were suitable for chemical bonding with thethiol-functionalized molecules. NiFe also demonstrated excellent etchingresistance in widely used dichloromethane solvent for dissolving moleculardevice elements. NiFe also reduced the mechanical stress induced deformities inother FM metals like cobalt. This paper also discusses the successfulutilization of NiFe electrodes in the magnetic tunnel junction based moleculardevice fabrication approach. This research is expected to address the knowledgegap blocking the experimental development of FM based MSDs.

Solution-processed zinc oxide (ZnO) thin-film transistors (TFTs) obtained viahydrolysis/pyrolysis of an organic precursor present an excellent technique toobtain high performance electronic devices with low manufacturing cost. In thecurrent work, we propose the use of an alternative deposition method, based on apolymeric precursor route (known as Pechini), to obtain solution-processed ZnOcompact films as the active layer of TFTs. The elimination of the organic phaseand the formation of inorganic thin-films was carried out by thermal treatmentat different temperatures (ranging from 200°C to 500°C) and atdifferent times (from 5 min to 2 hours), being monitored by UV-vis and infrared(IR) optical absorption spectroscopy. It was observed that, for temperaturesabove 400°C and treatment times superior to 30 min, the organic phasewas completely eliminated, remaining only the inorganic (metal oxide) phase. Theoptical bandgap of the resulting ZnO films, determined from UV-vis absorption,is about 3.4 eV. The electrical characteristics (output and transfer curves) ofthe obtained devices demonstrate the feasibility of Pecchini method to buildsolution-processed metal oxide TFTs. The results for the electrical mobility ofthe majority charge-carriers (electrons) and for the threshold voltage were 0.39cm2.V-1.s-1 and 0.45 V, respectively.

The photosynthetic reaction center (RC) from the purple Rhodobacter (R.)sphaeroides bacterium is a protein with unique photoconversioncapability that can be exploited in hybrid systems for energy conversion. Wehave developed a tailored aryleneethynylene organic fluorophore (AE750) actingas efficient light harvesting antenna and successfully bioconjugated it to thephotosynthetic RC. We have also demonstrated that, under suitable conditions,the biohybrid AE750-RC system can outperform the energy photoconversion abilityof the native protein.