A new solution-processed technique of floating film transfer method (FTM) is proposed for depositing organic thin film semiconductor. Organic field-effect transistors (OFETs) have been fabricated to evaluate the transport characteristics in poly(3-hexylthiophene) (P3HT) films deposited with FTM and spin-coating methodology. An enhancement of hole mobility was found in the FTM film by one order of magnitude as compared to that in spin-coated films. Absorption spectra as well as X-ray diffraction profiles represent well-grown lamella structures of P3HT with FTM transverse to the substrate, representing the advantage of this method suitable for the carrier transport.

Ambipolar field effects in poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61 -butyric methyl ester (PCBM) composite films have been studied. At ratios of x = [PCBM]/([P3HT]+[PCBM]) = 0.67 -0.9, an ambipolar transport appeared. Hole and electron mobilities were 5:0 Â 10 À5 and 2:5 Â 10 À4 cm 2 /(V s), respectively, at x ¼ 0:75. The hole mobility of 1:4 Â 10 À3 cm 2 /(V s) in pure P3HT decreased by blending with PCBM. By increasing the PCBM content, the electron mobility increased to 1:0 Â 10 À2 cm 2 /(V s) in pure PCBM. The threshold voltage in pure P3HT for p-type transport increased upon blending of PCBM, indicating that PCBM depresses the induction of holes. On the other hand, the threshold voltages of PCBM for n-type transport decreased in composite films. The results are discussed taking into consideration the fact that P3HT enhances the induction of electrons in composite films and/or the hole injection from drain to channel.

To demonstrate the role played by the von Neumann entropy (vNE) spectra in quantum phase transitions we investigate the one-dimensional anisotropic SU(2) XXZ ⊗ spin-orbital model with negative exchange parameter. In the case of classical Ising orbital interactions we discover an unexpected novel phase with Majumdar-Ghosh-like spin-singlet dimer correlations triggered by spin-orbital entanglement (SOE) and having k 2 π = orbital correlations, while all the other phases are disentangled. For anisotropic XXZ orbital interactions both SOE and spin-dimer correlations extend to the antiferro-spin/alternating-orbital phase. This quantum phase provides a unique example of two coupled order parameters which change the character of the phase transition from first-order to continuous. Hereby we have established the vNE spectral function as a valuable tool to identify the change of ground state degeneracies and of the SOE of elementary excitations in quantum phase transitions. OPEN ACCESS RECEIVED

Ambipolar characteristics in an organic field-effect transistor (FET) with a bilayer structure consisting of poly(3-hexylthiophene) (P3HT) and a fullerene derivative (PCBM) are reported. P3HT was deposited by a floating film transfer method (FTM) with toluene solution on spin-coated PCBM. The FTM-deposited film was found to show relatively high hole mobility even when cast using toluene solution. Even after coating P3HT on PCBM by FTM, a relatively high n-type transport was obtained. This indicates that FTM employed in this study is a mild way to coat an organic thin film on an organic semiconductor layer in terms of minimizing the effect of carrier transport in the underlayer. The transport characteristics have been discussed in comparison with those of ambipolar FETs prepared by other methods previously reported.

Ambipolar organic field effect transistors ͑OFETs͒, consisting of a composite of polyhexylthiophene ͑PHT͒ and ͓6,6͔-phenyl C61-butylic acid methyl ester ͑PCBM͒, was converted into a p-or n-type OFET by insertion of a thin tetracyanoquinodimethane ͑TCNQ͒ or tetrathiafluvalene ͑TTF͒ buffer layer. The interface in the Au/TCNQ/PHT:PCBM composite transports hole but blocks electron, while the transported carrier was switched to electron with insertion of a TTF layer. The selective transport is probably due to vacuum level matching or temporal doping. High impedance in a complementary metal-oxide-semiconductor inverter was demonstrated with unipolarized ambipolar FETs, resulting in a decrease in the through current.