||In this study, the characteristics and application to light sensor of organic thin-film transistors (OTFTs) fabricated with 5,11-bis(triethylsilylethynyl) anthradithiophene (TES-ADT) as a semiconducting layer by drop casting have been investigated. The average mobility of the TES-ADT (1 wt % TES-ADT in anisole) OTFTs subjected to thermal annealing treatment at 60 ℃ and 0.1 atm for 30min exhibits (6.50 ± 3.58) × 10^-2 cm^2/Vs, which is better than those of the devices subjected to heat treatment at 90 ℃ and 120 ℃. The optimal characteristics of the five OTFTs fabricated with TES-ADT in chlorobenzene solution can achieved the mobility of 0.21 cm^2/Vs and threshold voltage was less than 2 V. Following is the observed order of performance of TES-ADT OTFTs for several solvents: chlorobenzene > toluene > anisole > chloroform > 1,2-dichlorobenzene. On the other hand, the characteristics of device exhibit quite stable until 150 days. The electrical characteristics degraded slightly when device after 300 days of
The effects of visible light and UV illuminations on the electrical and photosensing properties of the TES-ADT and 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-PEN) thin film transistors were investigated. The mobility, threshold voltage, and maximum number of interface traps for the TES-ADT OTFT under dark and visible light with different light intensities were found to be 5.95 x10^-2 cm^2/Vs, 4.8 V, and 1.01x10^12 1/eVcm^2, and 5.20 x10^-2 cm^2/Vs, 21.4 V, and 2.04x10^12 1/eVcm^2 of 729 Lux ; 1.81 x10^-2 cm2/Vs, 30 V, and 4.13x10^12 1/eVcm^2 of 1307 Lux ; and 4.81 x10^-2 cm^2/Vs, 31.6 V, and 5.71x10^12 1/eVcm^2 of 4890 Lux, respectively. The TES-ADT OTFT under visible light illumination exhibits a high photosensitivity, 1.53x10^6 of 729 Lux, 7.52x10^3 of 1307 Lux, and 1.61x10^5 of 4890 Lux at VG=6 V, 4 V, and 5 V, respectively. However, the TIPS-PEN OTFT under visible light illumination were found to be 8.78 of 729 Lux, 279 of 1307 Lux, and 8250 of 4890 Lux at VG=5 V, 2 V, and 4 V, respectively. On the other hand, the photosensitivity of TES-ADT and TIPS-PEN OTFTs subjected to UV illumination at 365 nm were found to be 2.97 x10^6 (VG= 2 V) and 3.77 x10^4 (VG= 4 V), respectively. In other words, the light sensitivity of TES-ADT OTFT is larger than that of TIPS-PEN OTFT under UV and visible light illumination, which is due to the absorption coefficient of TIPS-PEN larger than that of TES-ADT.
Under 729 Lux intensity of visible light illumination for 1 hour, The threshold voltage and maximum number of interface traps for the TES-ADT OTFT is from 1.3 to 16.6 V and 9.66x10^11 to 1.88x10^12 1/eVcm^2, respectively. However, TIPS-PEN OTFT exhibit quite stable characteristics.
Finally, studied on the optoelectronic memory elements for the photoresponsive TES-ADT OTFTs subjected to 729 Lux intensity of light illumination (writing) and turning off light source (erasing) have been carried out. The maxima drain current shifts from -20.9 ?A to -23.2 ?A and from -18.9 μA to -20.2 μA during writing and erasing process, respectively. The threshold voltage and LOG (on/off current ratio) lies on 16.7~22.1 V and 5.06~5.13, 8.1~11.3 V and 6.0~6.4 during writing/ erasing process, respectively. It is indicated that the TES-ADT OTFTs is suitable for memory device applications.