Microscopic Evidence for Spatially Inhomogeneous Charge Trapping in Pentacene

Abstract

The comparatively high mobility of pentacene and its ability to be deposited on flexible substrates at low temperature [1,2] make it an attractive alternative to amorphous silicon in low-cost large-area electronics applications. Potential applications of pentacene thin-film transistors include display drivers, smart cards, and radio-frequency identification tags.[2±4]While pentacene thin-film transistors have exhibited usefully large mobilities (³ 1 cm 2 V ±1 s ±1 ) and on±off ratios (³ 10 6 ), [5] fabricating pentacene transistors with suitable performance for large-scale applications remains a challenge. In polycrystalline films, mobility is extremely sensitive to processing conditions, being dependent on crystallite size, [6±10]

Large-scale correlated study of excited state absorptions in naphthalene and anthracene

“…9,10 Because of the alternant nature of these molecules, different states, in addition to the point group symmetry ͑D 2h ͒, can also be classified according to their particle-hole parity ͑Ϯ͒. According to normal convention, we assign the ground state 1A g a negative ͑Ϫ͒ particle-hole parity.…”

Light-assisted deep-trapping of holes in conjugated polymers

“…nanoparticle ͉ single molecule spectroscopy ͉ charge injection T he nature of positive charge carriers (holes) in organic conjugated polymers remains obscure despite decades of materials and device research (1)(2)(3)(4)(5)(6)(7)(8)(9). Evidence suggests that there are at least two main types of holes, namely shallowly trapped (mobile) holes and deeply trapped holes (DTHs) (10)(11)(12).…”

Analysis of interface states of the pentacene organic thin-film phototransistor by conductance technique

“…Several techniques, such as photoelectron emission microscopy (PES) [36], potential imaging mapping [37], and scanning Kelvin probe microscopy (SKPM) [38,39] have been used to probe local defects originating from structural disorders, crystalline domain size, shape, and height of the pentacene layer itself. Metastable defects under bias voltage using space-charge limited current spectroscopy [40], deep charge traps using electric force microscopy [41] and shallow traps by using scanning tunneling microscopy (STM) [33] have been observed to clarify the charge transport mechanism at the interface between pentacene and insulating dielectric layers on various substrates [42]. The field-effect mobility and performance of an OTFT device depend also on deposition rate and substrate temperature that affect the morphology and molecular ordering of semi-crystalline organic semiconductors like pentacene [43,44].…”