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The properties of field effect transistors with organic insulator and semiconducting regions, fabricated with a top-gate architecture, have been investigated. Thin films (d≈30 nm) of regioregular poly(3-dodecylthiophene) were employed as the active semiconductor and the gate insulator was formed by a 500-nm-thick layer of poly(4-vinylphenol). Both were solution-processed on top of poly(ethylenetherephthalate) films, which were used as substrates. The output characteristics show a pronounced saturation behavior with an unconventional nonquadratic saturation current dependence on the gate voltage. Hence the (hole) mobility of 0.002–0.005 cm2/Vs has been estimated from the linear region of the transfer characteristics. The transistor turn-on occurs at a threshold voltage of approximately Vth=0 V, and the device can be operated with a supply voltage of between 15 and 20 V. As is usually observed for organic transistors, the inverse subthreshold slope (S) is very high, in our case S≈7 V/dec, by contrast with S≈200 mV/dec obtained for the similar material poly(3-octylthiophene) (P3OT) with silicon dioxide (SiO2) as an insulator. Furthermore, the subthreshold current depends on the drain voltage even though the transistor is electrically a long channel device with L=2 μm, notwithstanding the fact that this channel length is rather small for the present organic devices. To clarify these peculiarities numerical simulations have been carried out with a systematic variation of the relevant material parameters and assuming the existence of interface or bulk trap states. It turns out that both the high inverse subthreshold slope and the drain voltage dependence can be explained by recharging of trap states either at the interface or in the bulk. Considering the difference to the P3OT device with SiO2 as insulator it is proposed that interface traps are responsible for these effects, although one excludes the possibility that the film formation either on an organic substrate or on SiO2 leads to different bulk properties.

We present details of the fabrication, calculations, and transmission measurements for finite two-dimensional (2D) polymer photonic crystal (PC) slab waveguides, which were fabricated from a benzocyclobutene polymer on a low refractive index substrate from Teflon. A square air hole lattice (500 nm lattice constant, 300 nm hole diameter) was realized by electron beam lithography and reactive ion etching. Polarization and wavelength dependent transmission results show TE-like and TM-like stop gaps at 1.3 μm excitation wavelengths and are in good agreement with the calculated data obtained by 2D and three-dimensional finite difference time domain methods. Transmission was suppressed by 15 dB in the center of the TE-like stop gap for a PC length of ten lattice constants.

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Polymer solar cells based on poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene]:[6,6]-phenyl-C61-butyric acid methyl ester (1:3wt%) were fabricated using flexible 5×5cm2 polyester foils. These cells show a white-light power conversion efficiency of 3% comparable to smaller cells on glass published by other authors. Ten cells were arranged on one substrate with an active area of 25 and 175mm2 demonstrating a remarkably high reproducibility. It was found that the open-circuit voltage does not depend on the device area. An increase of the cell area caused a slightly lower short-circuit current, lower fill factor, and lower white-light power conversion efficiency.