為改善有機半導體場效載子移動率(Field Effect Mobility, 以µeff表示)偏低之缺點，本研究先探討pentacene通道層之基板在不同蒸鍍溫度(deposit temperature)對元件特性之影響，並找出最佳基板蒸鍍溫度；接著在基板於最佳蒸鍍溫度下，探討pentacene通道層摻雜不同量MoO3時對元件特性之影響，包括：輸出電流(output current, IDS)、µeff、臨界電壓(Threshold Voltage, 以VT表示)及電流開關比(on/off ratio, 以ION/IOFF表示)等；此外，以紫外光光電子能譜(Ultraviolet Photoemission Spectroscopy, 簡稱UPS)量測pentacene通道層摻雜不同量MoO3時其Fermi level與HOMO差距之變化，並驗證MoO3之添加是否有助於pentacene通道層電洞濃度(Hole Concentration)增加。研究結果顯示：
Pentacene通道層基板在蒸鍍溫度60℃、通道層與電極間加一層1 nm氟化鋰奈米結構時元件有最佳特性表現，其飽和電流(Saturation Current)為-11.6 µA、µeff為0.71 cm2/Vs、VT約為-21.2 V、ION/IOFF為1.6×106。基板在蒸鍍溫度60℃下、pentacene通道層添加MoO3時有助於元件飽和電流及µeff提升；當MoO3摻雜比在6.7%時元件有最大飽和電流(-38 µA)及µeff(1.6 cm2/Vs)，其值分別約為未添加MoO3時之3.3及2.3倍，然MoO3摻雜比過多時元件之µeff有降低之現象但仍較未添加MoO3時大；其VT會隨MoO3摻雜比提升而減小，當MoO3摻雜比在18.6%時其VT(-7.8 V)僅為未添加MoO3時之1/3、元件能量之消耗最少。當pentacene通道層開始摻雜MoO3時元件之ION/IOFF開始下降;當MoO3摻雜至9.1 ％時，其ION/IOFF值(1.9×105)與未摻雜MoO3時相較約僅減少一個數量級;而MoO3摻雜比提升至18.6 ％時，其ION/IOFF值(3.4×102)與未摻雜MoO3時相較則明顯降低(約減少四個數量級)，故控制適當MoO3摻雜比是必要的。UPS量測結果發現：隨MoO3摻雜比增加，pentacene通道層之Fermi level和HOMO越接近，此證實pentacene摻雜MoO3有助於通道層p-type特性提升及電洞濃度增加。本研究結果顯示：有機薄膜電晶體之pentacene通道層中摻雜適量MoO3時可明顯地提升元件特性。

The purpose of this research is to improve the field effect carrier mobility (µeff) of organic semiconductors. At the optimal substrate deposit temperature, the influence of dope concentration of molybdnum trioxide (MoO3) on the device properties, when the device was nano-structured with 1 nm lithium fluoride between the active layer and electrode to improve the efficiency of the carrier injection.
The results showed that the device at 60°C deposition temperature had the best performance. Compared with the conventional OTFTs, the saturation current was increased from -9.2µA to -11.6 µA, the field-effect mobility was improved from 0.53 cm2/Vs to 0.71 cm2/Vs.
When 6.7% molybdenum trioxide (MoO3) was doped in the pentacene as the active layer, the saturation current was increased from -11.6 µA to = -37.9 µA, the field-effect mobility was improved from 0.71 cm2/Vs to 1.6 cm2/Vs.
According to UPS measurements, the increase in conductivity is due to electron transfer from the highest occupied molecular orbital of the host molecules to very low lying unfilled states of embedded MoO3. The energy levels of these molecular are estimated by the energy levels of a neat MoO3 thin film with an electron affinity of 6.3 eV and an ionization energy of 9.3 eV. The Fermi level of MoO3-doped pentacene thin films rapidly shifts with increasing doping concentration towards the occupied states. Pinning of the Fermi level several 300 meV above the HOMO edge is observed for doping concentrations higher than 6.7 mol%. This finding verifies that MoO3 doping to pentacene channel improved the p-type property and hole concentration of the channel. This study demonstrates that MoO3 doping to the pentacene channel of organic thin film transistor is crucial to improve the performance of device.

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