Takahiro Kono

Dithienylbenzobis(thiadiazole) based organic semiconductors with low LUMO levels and narrow energy gaps

Novel OFET materials showing high mobility (0.77 cm2 V(-1) s(-1)) and good air-stability were developed using a benzobis(thiadiazole) (BBT) unit and the high FET performance was attributed to the low LUMO level and the film morphology.

Air-stable n-type organic thin-film transistor array and high gain complementary inverter on flexible substrate

Air-stable n-type organic thin-film transistor (TFT) arrays and a complementary inverter circuit were fabricated on a flexible substrate. A benzobis(thiadiazole) (BBT) derivative-based TFT showed excellent air- stability and performances such as an electron mobility of over 0.1 cm2/V s, a large ON/OFF ratio over 108 when combined with a cross-linkable olefin-type polymer gate dielectric. In addition, an organic complementary inverter that combined the BBT derivative and a pentacene TFT demonstrated a sharp switching behavior and a high gain of over 150. We attribute these excellent characteristics to a combination of the low-lying lowest unoccupied molecular orbital level of n-type semiconductor material and the low interface trap of the gate dielectric.

High performance n-type FETs based on heterocyclic ring systems with trifluoromethylphenyl groups

High performance n-type FETs have been accomplished by using novel heterocyclic systems with trifluoromethylphenyl groups. To enhance intermolecular interactions, selenophene rings were introduced. Some FET devices showed higher electron mobilities than 0.1 cm2V-1s-1. The mobilities of the selenophene-containing materials were higher than those of the corresponding thiophene analogues. The relationship between the structures and FET characteristics have been investigated. The threshold voltages were reduced by introducing heterocyclic units with higher electron affinity.

Enhancing the photocurrent in high-photovoltage organic solar cells by doping

We obtained a 50% improvement in photocurrent with a photovoltage of 1.0 V by impurity doping organic photoactive codeposited films consisting of fullerene and a novel organic semiconductor. A reduced cell resistance and the formation of band bending were revealed to be the main reasons for the doping-induced improvement in photocurrent. A conversion efficiency of 3.8% was observed.