五苯環素有機光感測電晶體之電場效應

Abstract

在本研究中，將甲基丙烯酸甲酯做為閘極介電層的五苯環素有機薄膜電晶體對光感測做研究，有機五苯環素元件的感光靈敏度在電場增強下大幅提升，而垂直電場提升的光感測靈敏度遠大於水平電場，同時也發現五苯環素在不同波長的光源下有不同的光反應，在相同的強度下對於藍光的反應較大，光靈敏度也在電場增強下提升到92A/W 左右，遠高於未施加電場增強的感光元件許多，其中光照產生的電流我們更發現可以分為兩大主因—1.光照造成臨界電壓改變而產生的增加電流。2.受光照激發電子電洞對產生的光電流。而電場增加的光電流主要是由臨界電壓改變產生的光電流，經過一系列不同光強及長時間的量測，我們發現電場強度決定了臨界電壓改變的上限也決定了感光的動態範圍，而光強決定了到達臨界電壓改變上限的反應時間，同時我們利用對於相同和不同光強度的重複量測來證實在實際應用上的可行性；相關研究是在博士班學長高士欽協助下共同進行。

In this study, the pentacene-based with PMMA dielectric was fabricated to be a phototransistor. It was found that the electric field can enhance the photoresponsivity of pentacene-based phototransistor and. the device channel modulation on the device photoresponsivity also was discussed. The pentacene-based device has the different photoresponsivity under different wavelength. The device photoresponsivity under blue light illumination has maximum value in the examined entire light source. The photoresponsivity can reach 92A/W when applying positive gate bias to the device. The better photo-sensible characteristics of phototransistor can be obtained by using positive electric field. After periodically measuring the light-induced threshold voltage shift and the photocurrent, the pentacene-based phototransistor provide sensible photoresponsivity in low power light intensity ranged from 50 □W/cm2 to 600 □W/cm2. In this study, we separated the device photocurrent into two main parts: (1) positive light-induced threshold voltage shift contribute to extra current. (2) light-induced hole-electron pairs generate extra current. When excluding the light-induced threshold voltage shift effect, the photocurrent became small and the difference between different light intensity was reduced. It was found that the device photoresponsivity is determined by the light-induced threshold voltage shift.