Organic field-effect transistors using single crystals

Abstract

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm 2 Vs −1 , achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

In situ measurement of exciton energy in hybrid singlet-fission solar cells

“…Pentacene is an attractive material for a sensitizer as it under goes efficient singlet fission [11][12][13] and has high hole mobility 14 , but the triplet energy is challenging to determine because of the van ishingly small photoluminescence quantum yield of pentacene 10,15 . In the solid state the triplet energy has been measured indirectly using variable temperature host guest fluorescence 16 , electron backscattering from crystalline pentacene 17 , and inelastic tunnel ling spectroscopy on amorphous pentacene 18 .…”

Correlation between thermal fluctuation effects and phase coherence factor in carrier transport of single-crystal organic semiconductors

“…This observation also holds true for other organic semiconductors such as tetracene, dianthrathiophene (DAT)-V, and dinaphtho [2,3- The recent progress in the fabrication technology of organic single-crystal semiconductors and thin-film field-effect transistors with very high carrier mobility up to 40 cm 2 /V Á s requires us to elucidate the mechanisms of carrier transport in organic semiconductors, which are assemblies of p-conjugate molecules weakly bonded by van der Waals interactions. 1, 2 Observations of the crossover from the hopping transport of localized carriers to bandlike transport with a diffusive nature are expected to provide us with clues allowing us to reveal the carrier transport mechanisms.…”

Remarkably low flicker noise in solution-processed organic single crystal transistors

“…In striking contrast to such disordered organic compounds, solutionprocessed single crystals composed of organic molecules exhibit an excellent mobility of up to 15 cm 2 V −1 s −1 ref. [1][2][3]8 , which has motivated intensive research to explore not only the coherent (band-like) charge transport physics 27,28 , but also functionalities for next-generation (opto)electronic applications 29,30 . However, a subject under consideration still remains: how the charge carrier transport mechanism correlates to the 1/f noise, and to what extent the noise level can be reduced in a practical electronic circuit.…”