Field effect mobilities

Figure 14-13. Evolution of the field-effect mobility of OFETs for five organic materials polythio-phenc (PT) and its derivatives, qualerthiophcne (4T), scxithio-phenc (6T), dihcxyl-sexithiophene (DH6T). and pcntaecnc.

Another significant feature found recently is that the effect of the chain length on the field-effect mobility is much less pronounced than indicated in earlier reports [68, 74]. The increase from 4T to 6T corresponds to about a factor of ten, while that from 6T to 8T is only two (the low mobility measured for the dihexyl-substituted 8T must be ascribed to the difficulty in synthesizing and purifying this compound 75 J). Representative data arc gathered in Table 14-1. Also note that the effect of alkyl end substitution is reduced by a factor of two to three (as compared to up to 1000 in earlier reports 68 ). 

Table 14-1. Typical field-effect mobility (in cm2 V 1 s ) of unsubsliluled and dialkyl-subsliluled oli-gothiophenes.

Figure 14-21. Varialion of the field-effect mobility as a functior of the conductivity of various) doped polyfdodccyloxy-terlhienyl) (PDOT), a polylhiophene derivative (adapted from Ref. II3 ).

An alternative method to estimate the field-effect mobility consists of using the transconduclanee in the linear regime, given by Eq. (14.32). We noie that the... 

Figure 14-23. Variation of the field-effect mobility, as deduced by differentiating the drain current at Vt,=-i V, as a function of the gale voltage, for the same device as in Figure 14-22.

Chen, C.-Y. Kanicki, J. 1996. High field-effect-mobility a-Si H TFT based on high deposition rate PECVD materials. IEEE Electron Device Lett. 17 437-439. 

As shown in Fig. 5.6b, these TFTs exhibit good electrical characteristics, with field-effect mobility (calculated from the transconductance in the... 

Figure 12.3. Benchmark of peer-reviewed academic reports of organic semiconductor device field-effect mobility versus time of report. All data points are for spin-coated organic semiconducting transistors. Solid points are derived from the benchmark study completed in 2002 by Brazis and Dyrc at Motorola (unpublished). The curve is a calculated estimation, based on these data, of what the expected mobility values will be in the future. The open points are data derived in 2005 from the public journals for verification of the 2002 prediction.6 38... 

Assadi, A. Svensson, C. Willander, M. Inganas, O. 1988. Field-effect mobility of poly(3-hexylthiophene). Appl. Phys. Lett. 53 195-197. 

Geens, W. Tsamokuras, D. Poortmans, J. Hadziioannou, G. 2001. Field-effect mobilities in spin-cast and vacuum-deposited PPV-type pentamers. Synth. Met. 122 191-194. 

TFT field-effect mobility compensation OLED threshold voltage compensation... 

Figure 9.7a shows an example of a-Si H TFT transfer characteristics in linear regime with different W/L ratios and an example of a-Si H TFT characteristics in saturation regime with W/L = 170 pm/6 kpm. A threshold voltage (Vth) of 10 = 11 V, a field-effect mobility (p) of 0.2 0.3 cm2/(V s), a subthreshold swing slope of 0.8 dec/V, and a current ON/OFF ratio of larger than 106 for VGS from —10 to 30 V were obtained from these curves for a-Si H TFTs. These devices were used in 4-a-Si H TFTs AM-PLEDs. The electrical properties of a-Si H TFTs used in 3-a-Si H TFTs AM-PLEDs are described in Ref. [18]. 

Maennig B, Pfeiffer M, Nollau A, Zhou X, Leo K, Simon P (2001) Controlled p-type doping of polycrystalline and amorphous organic layers self-consistent description of conductivity and field-effect mobility by a microscopic percolation model. Phys Rev B 64 195208... 

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