具有高介電常數、低漏電流和良好的機械穩定性的可低溫製程的閘極絕緣層被廣泛應用在可撓式元件、可穿戴型裝置。目前有機光感測薄膜電晶體所遭遇的困難為其於可見光的響應度普遍不高及操作電壓太高不易應用，為解決此困境，本研究團隊將利用原子層沉積(ALD)高介電係數閘極絕緣層搭配超薄的 Cu:Ag 金屬電極來進一步減少閘極絕緣層的厚度，有效降低驅動電壓、提升驅動電流，並搭配高效率 SubPc 吸光層，放大可見光波段光感應電流進而有效提升響應度。
本論文將以 Pentacene 作為主動層材料，並分為兩部分來探討，第一部分為製作低電壓有機薄膜電晶體，元件使用原子層沉積(ALD)雙層 High-K 閘極絕緣層 ALD-HfO2 與 ALD-Al2O3沉積於薄化的 Cu:Ag 閘極之上，增加驅動電流、有效降低電晶體之驅動電壓，並進行電容量測確定 ALD-HfO2 與 ALD-Al2O3 的介電係數，經由實驗結果得知以薄化的Cu:Ag 合金作為閘極搭配 ALD 的絕緣層可有效降低驅動電壓。另外可由 AFM 材料分析得知薄化後的 Cu:Ag 閘極仍保有相當平滑的表面(Rms < 1 nm)，代表閘極絕緣層能妥善沉積於閘極上。接著變化閘極絕緣層的厚度，取最佳化參數並接續製作成低電壓有機光感測薄膜電晶體。
第二部分為製作成低電壓有機光感測薄膜電晶體，在 Pentacene 通道層上共蒸鍍高吸收效率混合吸光層 SubPc，使用劉舜維教授實驗室已知的鍍率，元件製作完後使用 UVVisible 光譜儀量測薄膜可見光波段之吸收度，量測照光後變化的電特性，並計算出分別之光響應度，光靈敏度、EQE 與偵測度。
從第一部分可以得知使用單層 ALD-HfO2 閘極絕緣層，因其表面與 ALD-Al2O3 相比較疏水，主動層 Pentacene 沉積於上擁有較大顆的晶粒因此具有較好的電特性後，第二部分通過調變吸光層(SubPc)厚度(40、60、80 nm)至元件電特性及響應度達最佳值，並利用 UV-Visible 光譜儀量測薄膜之光吸收度，驗證 SubPc 之厚度變化在可見光波段的吸收度確實明顯的提升。

Organic Phototransistors (OPTs) have great potential for application in IoT (Internet of Things) photosensor, biomedical sensing, display, etc. We will develope an organic ambient light thin film phototransistor combining with low-temperature-processed atomic layer deposited (ALD) ultra-thin High-K gate insulator at glass substrate. The combination and architecture of these layer’s materials will achieve the goal of excellent light sensing device with low operating voltage, high absorption efficiency, high stability and high responsivity for ambient light wavelength.
The current problems encountered by organic phototransistor are that the low responsivity in visible light and the high operating voltage, which limits its applicability. To solve this dilemma, we will develop the optimal conditions of the atomic layer deposited ultra-thin HighK gate insulators combining with the ultra-thin metal film (Cu : Ag) as metal gate to further reduce the thickness of the gate insulator layer, to significantly reduce the operating voltage (less than 2V) and amplifying the light-induced current to effectively improve the responsibility.
Moreover, we will develop a hybrid structure combining the high-efficiency visible light absorption layer SubPc absorption band (500 ~ 650 nm) and Pentacene absorption band (550 ~ 700 nm) as the light-absorbing layer. Because the active layer of the pentacene and the lightabsorbing layer are both organic materials, they can be continuous evaporation and has the advantage of low cost. In this project, our team will develop high performance organic phototransistors with the ultra-low operating voltage, high stability and high responsivity in the visible light.
This project is the first time to use SubPc as the visible light absorbing layer of the pentacene-based organic phototransistor, and the development of ultra-thin Cu : Ag metal electrodes to further reduce the thickness of the High-K gate insulator layer, significantly reduce the operating voltage. In summary, this project is developed with high responsivity (~13.2 A/W) in the visible light and low operating voltage (< 2 V) organic light sensing thin film transistors. Which is expected to make an important contribution to the application of low power
consumption organic phototransistor.

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