Charge carrier mobility in organic molecular materials probed by electromagnetic waves

Abstract

Charge carrier mobility is an essential parameter providing control over the performance of semiconductor devices fabricated using a variety of organic molecular materials. Recent design strategies toward molecular materials have been directed at the substitution of amorphous silicon-based semiconductors; accordingly, numerous measurement techniques have been designed and developed to probe the electronic conducting nature of organic materials bearing extremely wide structural variations in comparison with inorganic and/or metal-oxide semiconductor materials. The present perspective highlights the evaluation methodologies of charge carrier mobility in organic materials, as well as the merits and demerits of techniques examining the feasibility of organic molecules, crystals, and supramolecular assemblies in semiconductor applications. Beyond the simple substitution of amorphous silicon, we have attempted to address in this perspective the systematic use of measurement techniques for future development of organic molecular semiconductors.

Diversity-oriented synthesis of tetrathia[8]circulenes by sequential C–H borylation and annulation

“…21 The maximum transient conductivity (φΣµ) of 1b was found to be significantly smaller than those of 1d-1i (Figure 4), suggesting that the face-to-face stacking in the solid state is an important factor in providing a transportation pathway for charge carriers in 1. The conductivity transient was not quenched in an SF 6 environment, suggesting positive holes as the major charge carriers.…”

Unraveling Unprecedented Charge Carrier Mobility through Structure Property Relationship of Four Isomers of Didodecyl[1]benzothieno[3,2‐b][1]benzothiophene

“…FP-TRMC is a completely non-contact device-less method where the average lateral motion of charge carriers (parallel to the quartz substrate), photogenerated in the bulk of thin fi lm samples, is monitored through GHzorder microwave spectroscopy (the interested reader can fi nd additional information relative to the FP-and FI-TRMC measurement techniques in the Experimental Section, Figure S6 (Supporting Information) and recent articles and review articles). [ 10,15,32 ] As shown in Figure 3 a, all drop casted fi lms of 1 -4 gave conductivity transients ( ϕ Σ µ ) with a prompt rise and slow decay upon injection of photogenerated charge carriers ( ϕ and Σ µ represent the quantum yield of generation and sum of the mobilities of positive ( µ + ) and negative ( µ − ) charge carriers, respectively). Interestingly, 2 provided the highest photoconductivity with a maximum value of ( ϕ Σ µ ) max = 1.4 × 10 −3 cm 2 V −1 s −1 .…”

“…Holding great promises for the rapid screening of a large number of semiconductor/dielectric pairs, this technique has also recently proved its effi ciency for quantitative probing of interfacial trap sites. [ 10,[15][16][17] It must be emphasized that FI-TRMC is complementary to OFET and Hall-effect methods because it probes charge transport over shorter lengthand time-scales, allowing thus to investigate the elementary steps of charge transport. FI-TRMC will certainly contribute to elucidate the charge transport mechanism exhibited by weakly van der Waals bonded systems.…”

Emergence of Highly Elaborated π-Space and Extending Its Functionality Based on Nanocarbons: New Vistas in the Fullerene World

“…146 To evaluate intrinsic chargecarrier mobilities (®), the flashphotolysis time-resolved microwave conductivity (FP-TRMC) measurement has served as an electrodeless method in conjugated organic materials. 147 In collaboration with Prof. Shu Seki (Osaka University), we have evaluated the conductivity of EMFs and their derivatives using the FP-TRMC method (Figure 26). The FP-TRMC measurements of a single-crystal of La@C 2v (9)-C 82 (Ad) exhibited anisotropic and extremely high electron mobility of ® > 10 cm 2 V ¹1 s ¹1 along the c axis and long axis direction, whereas the dropcast thin film of La@C 2v (9)-C 82 (Ad) exhibited much smaller values (7 © 10…”