UV ozone treatment for oxidization of spiro-OMeTAD hole transport layer.

For practical application of perovskite photovoltaic devices, it is vital to choose an appropriate carrier extraction material with high mobility, high conductivity, and appropriate molecular energy levels. One of the most frequently used hole transport materials, spiro-OMeTAD, is known to show an improvement in its electrical properties after the oxidation reaction. However, this oxidation reaction is generally accomplished by simple atmospheric exposure, often taking one or more nights under atmospheric conditions, and thus the development of a rapid oxidation strategy without the degradation of device performance is strongly required. Here, we propose a rapid and reproducible oxidation route employing a UV ozone treatment process that enables quick oxidation of spiro-OMeTAD in solution, as short as 30 seconds. Optical and electrical characterization reveals that this method modifies the highest occupied molecular orbital energy level of spiro-OMeTAD to reduce the voltage loss, and also improves the conductivity and mobility, leading to the enhancement in the photovoltaic properties. This finding will provide useful insights into the further development of spiro-OMeTAD-based perovskite solar cell devices.

Pyrolysis of Iron-Containing Polyanilines under Micropore Generation Control: Electrocatalytic Performance in the Oxygen Reduction Reaction.

Pyrolyzed iron-containing polyaniline (C-Fe-PANI) is one of the most promising candidates as a non-precious metal based electrocatalyst for oxygen reduction reaction (ORR). Although the ORR activity depends on the surface area arisen from pyrolysis-generated micropores on C-Fe-PANI particles, the micropore generation is hindered by pyrolysis-formed iron nanoparticles (Fe NPs) embedded inside C-Fe-PANI particles. Here, we demonstrate the pyrolysis of iron-containing PANIs under suppression of micropore-generation hindrance by blocking the Fe NPs formation. The higher-molecular-weight (MW: 100,000) PANI was dispersed in an FeCl3 solution before pyrolysis for preventing FeCl3 penetration inside PANI particles. As a result, as compared to the case of lower-MW (5,000) PANI, the Fe NPs formation was more suppressed inside catalyst particles to give 1.9 (1.8) times micropore volume (specific surface area), leading to a 11 % higher current density in ORR electrocatalytic performance test in acidic media.

Microcrystalline array structures induced by heat treatment of friction-transferred organic semiconductor films.

The correlation between molecular orientation and optoelectrical properties is most critical to the future design of molecular materials. We made highly-anisotropic microcrystalline array structures with an organic semiconductor, a methoxy-substituted thiophene/phenylene co-oligomer (TPCO), by depositing it on friction-transferred poly(tetrafluoroethylene) (PTFE) layers fabricated on substrates with several heat treatments. Polarising microscope observation, polarised emission and absorption spectra measurements indicated that the TPCO molecules aligned along the drawing direction of PTFE. Using these films, we fabricated two types of field-effect transistors (FETs) and compared them with those using non-heated TPCO films which provide aligned pleats structures. Ones had the channel length direction parallel to the drawing direction of PTFE and the others had the channel length direction perpendicular to that drawing direction. As for the microcrystalline array films, the mobility ratio of the former FET to that of the latter device was about 27 in the saturation region, while the emission polarisation ratio was 4.5. The heat treatment promoted the crystal growth to enhance the mobility while retaining the high anisotropy. The results demonstrate that the heat treatments of the TPCO films on the friction-transferred layers were useful for controlling crystallinity and orientation of the molecules.

Sumanenemonoone imines bridged by redox-active π-conjugated unit: synthesis, stepwise coordination to palladium(II), and laser-induced formation of nitrogen-doped graphitic carbon.

Sumanenemonoone imine compounds bridged by a redox-active π-conjugated unit on the basis of the conversion between 1,4-phenylenediamine and 1,4-benzoquinonediimine were synthesized and characterized. The stepwise coordination of the imino groups to Pd(II) in the sumanenemonoone imine compound bridged by 1,4-benzoquinonediimine was indicated by the titration experiment. Laser irradiation of a film of the metal-free quionediimine gave nitrogen-doped graphitic carbon, which was supported by an increase in conductivity and by Raman spectroscopy. The obtained graphitic carbon corresponds to carbonous compounds thermally treated at approximately 700-1000 °C. The ratio of nitrogen and carbon relative to that in the starting compound was nearly completely retained (5.4% decrease).