SOLUTION-PROCESSED LOW-VOLTAGE ORGANIC FIELD-EFFECT TRANSISTORS BASED ON ANTHRADITHIOPHENE MOLECULAR SOLIDS
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Solution-processed low-voltage organic field-effect transistors (OFETs) have attracted much attention due to their possible application in the fabrication of devices with large area, light weight, low cost and flexibility. This project includes the design and optimization of solution-processed low-voltage organic phototransistors (OPTs) and biosensors which respond to bovine serum albumin (BSA). The OPT device was based on triethylgermylethynyl-substituted anthradithiophene (diF-TEG ADT). Two kinds of dielectric materials were used: 80-nm-thick potassium alumina (PA) and 300-nm-thick thermally grown SiO2. To investigate application in a moist environment, the performance at different relative humidities (R.H.’s) was characterized. Results showed that the device was very stable in high humidity, and exhibited good performance even up to 85% R.H. A major change in drain current (I_DS) was observed when connecting or disconnecting the gate electrode to the device in the dark once the photocurrent was generated. This feature may motivate the application of diF-TEG ADT-based phototransistors as multistage photo-controlled memory devices. For the biosensor device, a sensitive (10 ng/mL) sensor platform for bovine serum albumin (BSA) detection using small molecule-polymer blend transistor was developed. Triethylsilylethynyl-substituted anthradithiophene (diF-TES ADT) was used as the small molecule semiconductor. Blending poly(methyl methacrylate) (PMMA) with diF-TES ADT improved the environmental and electrical stability since they are reported to form a vertically phase-separated structure. The high stability in 0.05 PBS solution and small leakage current also contributed to the application of this device as a biosensor. Moreover, the solution rheology of polymers makes it easier to print them on large flexible substrates.