Alkyl chain length dependence of the field-effect mobility in novel anthracene derivatives

We report six asymmetric alkylated anthracene-based molecules with different alkyl side chain lengths for use in organic field-effect transistors (OFETs). Alkyl side chains can potentially improve the solubility and processability of anthracene derivatives. The crystallinity and charge mobility of the anthracene derivatives may be improved by optimizing the side chain length. The highest field-effect mobility of the devices prepared here was 0.55 cm(2)/(V s), for 2-(p-pentylphenylethynyl)anthracene (PPEA). The moderate side chain length appeared to be optimal for promoting self-organization among asymmetric anthracene derivatives in OFETs, and was certainly better than the short or long alkyl side chain lengths, as confirmed by X-ray diffraction measurements.

Naphtho[2,1-b:3,4-b']dithiophene-based bulk heterojunction solar cells: how molecular structure influences nanoscale morphology and photovoltaic properties

Organic bulk heterojunction photovoltaic devices based on a series of three naphtho[2,1-b:3,4-b']dithiophene (NDT) derivatives blended with phenyl-C71-butyric acid methyl ester were studied. These three derivatives, which have NDT units with various thiophene-chain lengths, were employed as the donor polymers. The influence of their molecular structures on the correlation between their solar-cell performances and their degree of crystallization was assessed. The grazing-incidence angle X-ray diffraction and atomic force microscopy results showed that the three derivatives exhibit three distinct nanoscale morphologies. We correlated these morphologies with the device physics by determining the J-V characteristics and the hole and electron mobilities of the devices. On the basis of our results, we propose new rules for the design of future generations of NDT-based polymers for use in bulk heterojunction solar cells.

High performance organic nonvolatile flash memory transistors with high-resolution reduced graphene oxide patterns as a floating gate

High-performance organic nonvolatile memory transistors (ONVMTs) are demonstrated, the construction of which is based on novel integration of a highly conductive polymer as a semiconductor layer, hydroxyl-free polymer as a tunneling dielectric layer, and high-resolution reduced graphene oxide (rGO) patterns as a floating gate. Finely patterned rGO, with a line width of 20-120 μm, was embedded between SiO2 and the polymer dielectric layer, which functions as a nearly isolated charge-trapping center. The resulting ONVMTs demonstrated ideal memory behavior, and the transfer characteristics promptly responded to writing and erasing the gate bias. In particular, the retention time of written/erased states tended to increase as the rGO line width was reduced, implying that the line width is a critical factor in suppressing charge release from rGO. Using a 20-μm-wide rGO pattern, a nonvolatile large memory window (>20 V) was retained for more than 5 × 10(5) s, which is 50 times longer than non-patterned rGO films.