## 1 Introduction  
Organic semiconductor dosimeters have been introduced recently [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. Organic thin film transistors (OTFT) have gained special interest in radiation dosimetry applications as a new class of potentially tissue-equivalent radiation dosimeters. The sensitivity of such dosimeters is generally defined as the ratio of the channel conductance change to the absorbed dose and parameters, such as off current, on current, threshold voltage Vth, and current ratio, can be monitored [13, 14, 15, 16]. In a bottom-gate top-contact design with poly(3-hexylthiophene-2,5-diyl) (P3 HT) as a semiconductor on a silicon dioxide (SiO2) dielectric layer, [PERSON] et al. found a decrease in the on current by a factor of two, an increase in off current by a factor of 150, and a decrease in the mobility after a total dose of 41,000 cGy. The threshold voltage was shifted negatively due to positive charge accumulation in the silicon dioxide [13]. In a pentacene OTTF, after exposure to a total dose of 100 Gy, the off current was increased 320 times, which resulted in a sensitivity of 20 nA/Gy. The threshold voltage shift resulted in a sensitivity of 0.3 V/Gy [14]. Furthermore, the same group introduced CuPc OTTF dosimeter after \(\gamma\)-irradiation, with a minimum dose of 10 cGy, increasing to a maximum dose of 100,000 cGy. Three and five OTTFs, respectively, were connected in parallel to increase the resolution of measuring the off current. The measured sensitivity from off current shifts after irradiation was of 0.02/cGy for \(\Delta\)I\({}_{\text{OFF}}\)/I\({}_{\text{OFF}}\). From the V\({}_{\text{th}}\) shift measured at a constant drain current of 10\({}^{-7}\) A, the sensitivity of 1.5 \(\times\) 10\({}^{-4}\)/cGy for \(\Delta\)V\({}_{\text{TH}}\)/V\({}_{\text{TH}}\) was observed for a total dose of 100,000 cGy [15]. [PERSON] et al. introduced a rubrene semiconductor OTFT as a dosimeter for electron beam irradiation [17]. They showed that electrons can induce traps not only in SiO\({}_{2}\) dielectric and Si/SiO\({}_{2}\) interface, but also in the organic semiconductor. They found a significant mobility change after irradiation of all layers of transistors and negligible change of mobility after irradiation of dielectric only (before rubrene deposition), which proves that radiation mainly affects the organic semiconductor. [PERSON] and colleagues only partially related the reduction of charge carrier mobility with an increase of charge carrier traps in 6,13-bis(trisisopropylsilylethylynyl)-pentacene (TIPS-pentacene)-based field effect transistors with organic dielectric irradiated by high energy protons [18]. The high-energy protons induce defects in the organic dielectric and strains in the TIPS-pentacene layer leading to mobility reduction. The sensitivity of OTFT dosimeters can be improved by introducing additional carrier traps to the organic polymer or dielectric material. This distribution of traps within the band gap are associated with donor and acceptor atoms, with other impurity atoms in the bulk of the semiconductor, or with \"dangling bonds\" that occur at defects or exterior surfaces and grain boundaries. [PERSON] et al. improved the response of OTFTs to radiation by increasing the density of trap states by introducing impurity atoms into the bulk of the semiconductor. The TIPS-Pentacene and Polystyrene (TP-PS) blend was used as a semiconductor material in OTFTs for sensing gamma rays from a cobalt-60 (60) radiation source [19]. Devices irradiated before deposition of the TP-PS (only dielectric layer) and devices irradiated after deposition of the semiconductor were compared to show the amount of charge trapped in the bulk semiconductor (TP-PS blend) and in the SiO\({}_{2}\)/TP-PS interface. The sensitivity of the SiO\({}_{2}\)/TP-PS detectors was significantly higher than the sensitivity of detectors irradiated before TP-PS deposition [19].