Volume 8, Issue 4, April 2015
Index of content:
- ORGANIC ELECTRONICS AND PHOTONICS
106(2015); http://dx.doi.org/10.1063/1.4917235View Description Hide Description
Amorphous indium-gallium-zinc-oxide (a-IGZO) is demonstrated as an electron transport layer (ETL) in a high-performance organic photodetector (OPD). Dark current in the range of 10 nA/cm2 at a bias voltage of −2 V and a high photoresponse in the visible spectrum were obtained in inverted OPDs with poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester active layer. The best results were obtained for the optimum a-IGZO thickness of 7.5 nm with specific detectivity of 3 × 1012 Jones at the wavelength of 550 nm. The performance of the best OPD devices using a-IGZO was shown to be comparable to state-of-the-art devices based on TiOx as ETL, with higher rectification achieved in reverse bias. Yield and reproducibility were also enhanced with a-IGZO, facilitating fabrication of large area OPDs. Furthermore, easier integration with IGZO-based readout backplanes can be envisioned, where the channel material can be used as photodiode buffer layer after additional treatment.
Correlation between thermal fluctuation effects and phase coherence factor in carrier transport of single-crystal organic semiconductors106(2015); http://dx.doi.org/10.1063/1.4916734View Description Hide Description
We find that the phase coherence factor derived from Hall effect measurements of single-crystal thin-film field-effect transistors of pentacene, which relates the intrinsic charge transport with the phase coherence, has a strong correlation with the thermal fluctuations of transfer energies between neighboring molecules. This observation also holds true for other organic semiconductors such as tetracene, dianthrathiophene (DAT)-V, and dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT). This gives us clues for constructing flexible molecular systems with high carrier mobility.
Uniaxially oriented polycrystalline thin films and air-stable n-type transistors based on donor-acceptor semiconductor (diC8BTBT)(F n TCNQ) [n = 0, 2, 4]106(2015); http://dx.doi.org/10.1063/1.4918288View Description Hide Description
We report the fabrication of high quality thin films for semiconducting organic donor-acceptor charge-transfer (CT) compounds, (diC8BTBT)(F n TCNQ) (diC8BTBT = 2,7-dioctylbenzothieno[3,2-b]benzothiophene and F n TCNQ [n = 0,2,4] = fluorinated derivatives of 7,7,8,8,-tetracyanoquinodimethane), which have a high degree of layered crystallinity. Single-phase and uniaxially oriented polycrystalline thin films of the compounds were obtained by co-evaporation of the component donor and acceptor molecules. Organic thin-film transistors (OTFTs) fabricated with the compound films exhibited n-type field-effect characteristics, showing a mobility of 6.9 × 10−2 cm2/V s, an on/off ratio of 106, a sub-threshold swing of 0.8 V/dec, and an excellent stability in air. We discuss the suitability of strong intermolecular donor–acceptor interaction and the narrow CT gap nature in compounds for stable n-type OTFT operation.
106(2015); http://dx.doi.org/10.1063/1.4917562View Description Hide Description
Vertical organic transistors withstanding high voltage bias were realized with an insulating silicon monoxide layer obliquely deposited on both the surface of the base electrode and sidewalls of the vertically oriented cylindrical nanopores. No noticeable insulating layer can be observed on the emitter electrode at the bottom of the cylindrical nanopores. The leakage current between the electrodes was suppressed and an operating voltage as high as 15 V was obtained. An on/off current ratio of 103–104 and an output current density of 5–10 mA/cm2 were achieved.