Masatoshi Saito

Highly balanced ambipolar mobilities with intense electroluminescence in field-effect transistors based on organic single crystal oligo(p -phenylenevinylene) derivatives

Single crystal organic field-effect transistors (FETs) based on highly luminescent oligo(p-phenylenevinylene) (OPV) derivatives are fabricated. Although OPV single crystal FETs show both p- and n- type FET operation, we found that an increase in the conjugation length of the OPV derivatives from three phenylene rings (P3V2) to four phenylene rings (P4V3) results in an improvement in the electron mobility by an order of magnitude, while retaining the high hole mobility. This molecular design, using P4V3, achieved an ambipolar light-emitting OFET with well-balanced high hole (0.12u2002cm2/Vu2009s) and electron (0.11u2002cm2/Vu2009s) mobilities, leading to intense electroluminescence.

Tuning of threshold voltage by interfacial carrier doping in organic single crystal ambipolar light-emitting transistors and their bright electroluminescence

Organic light-emitting field-effect transistors, based on a p-bis[(p-styryl)styryl] benzene (P5V4) single crystal, that possess high mobilities of over 0.1u2002cm2/Vu2009s for both electrons and holes were fabricated. For a small charge injection barrier and successive formation of high exciton density in the carrier recombination zone, the hole accumulation threshold voltage was significantly reduced by interfacial hole doping based on electron transfer from P5V4 molecules to a molybdenum oxide layer. The threshold voltage for hole accumulation was drastically decreased from −80±3 to 2±3u2002V, leading to dual charge injection and accumulation of a very high current density of J>100u2002Au2009cm−2 with intense edge electroluminescence.

Control of p- and n-type carriers by end-group substitution in oligo-p-phenylenevinylene-based organic field-effect transistors

Organic field-effect transistors (OFETs) consisting of vacuum-evaporated oligo-p-phenylenevinylene derivatives were prepared, and the device characteristics were evaluated. The fabricated OFETs showed typical p-type characteristics for methyl-substituted oligo-p-phenylenevinylene (OPV). A field-effect hole mobility of 0.13cm2V−1s−1 emerged with a threshold voltage of −33V and an on/off ratio of 5.8×105. On the other hand, OFETs showed typical n-type characteristics for trifluoromethyl-substituted OPV. A field-effect electron mobility of 0.013cm2V−1s−1 emerged with a threshold voltage of 45V and an on/off ratio of 4.2×104. The authors have observed clear changes from p-channel to n-channel conductions in OFETs by chemically modifying oligo-p-phenylenevinylenes.