| 摘要: | 有機光偵測器在光電轉換應用中雖然具有無窮潛力，但是目前大多數有機光電偵測器因為考量激子的拆解效率而使用本體異質結面 (bulk heterojunction)結構作為吸光主動層，但會導致較高的暗電流，而光偵測器的暗電流會影響元件之性能。因此，本研究引入阻擋層的概念，目的在於提升有機光偵測器的性能，實現低暗電流和高光電流的元件設計。實驗選用Poly(3-hexylthiophene)(P3HT)及[6,6]-phenyl-C61-butyric acid methyl ester(PCBM)作為元件的主動層，並研究使用五種不同的阻擋層，並對結果進行分析和討論。
首先，研究加入絕緣材料HfO2，結果證實有機光偵測器能夠達到降低暗電流效果，但無法提升光電流。接下來研究以氧化鋅前驅物生長之氧化鋅薄膜（Zinc oxide，ZnO）做為阻擋層，實驗結果發現薄膜厚度不同會導致元件性能有明顯差異。進一步利用市售功函數(Work function)4.3 eV和3.9 eV的ZnO墨水旋塗成膜作為阻擋層，發現加入高功函數的ZnO能有效抑制光偵測器的暗電流。而加入低功函數的ZnO則大幅增加暗電流和光電流。透過不同功函數的元件差異也展現ZnO功函數會影響元件的性能表現。最後，將兩種功函數ZnO墨水以適當比例混和，成功使有機光電偵測器能同時降低暗電流並提高光電流。在-1 V偏壓下，該元件的響應度達到0.62 A/W，偵測度為 1.84×10^12 Jones，外部量子效率為146.9 %，上升時間為16.5 µs和下降時間為106.5 µs。
;Organic photodetectors hold immense potential for convert light energy into electrical energy applications. However, most organic photodetectors use bulk heterojunction structures as their photoactive layers to increase exciton dissociation efficiency, but this can result in a high dark current, consequently impacting the device′s performance. To address this issue, this study introduces the concept of charge-blocking layers to enhance the performance of organic photodetectors, aiming to achieve low dark current and high photocurrent in the device design. The experiments employed Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the active layer materials and analyzed the results using five different blocking layers.
Firstly, the addition of the insulating material hafnium oxide (HfO2) confirmed the expected reduction in the dark current due to charge blocking effect, but the photocurrent was not increased. Subsequently, the zinc oxide (ZnO) blocking layer prepared by the precursor was investigated, revealing that different ZnO thicknesses would result in significant variations in device performances. Additionally, the commercially available ZnO inks with work functions of 4.3 eV and 3.9 eV were used as the blocking layers. It was found that the higher work function ZnO effectively suppressed the dark current of the photodetector. In contrast, adding lower work function ZnO led to a substantial increase in both dark and photocurrents. The differences observed in the devices with different work functions also indicate that the work function of ZnO affects the performance of the device.. Finally, by blending two types of ZnO inks with different work functions at an appropriate ratio, the organic photodetector can successfully achieve the reduced dark current and increased photocurrent, resulting in an overall performance improvement. At a -1V bias voltage, the optimal device demonstrated a responsivity of 0.62 A/W, detectivity of 1.84×10^12 Jones, and EQE of 146.9 %. The rise time of 16.5 µs and fall time of 106.5 µs. |
