基于有机半导体材料的光电探测器具有机械柔软性好，可溶液加工，易大面积生产，带隙可调等优点，可以很好的弥补硅基探测器在柔性可印刷电子器件应用上的不足。另外，由于近红外光电探测器在医疗应用、光纤通讯、质量检查、生物成像以及无人驾驶技术等领域具有重要意义，近些年来的许多研究都致力于将有机光电探测器的光谱响应拓宽到近红外区域。然而，有机光电探测器仍存在着许多亟待解决的问题，如低的光电响应，低的稳定性和特征波段选择性不足等，这限制了其在商业器件上的应用。针对有机光探测器固有的缺陷，本文设计了新颖的器件结构，将光学谐振器耦合到器件中，利用其独特的光场调控特性来改变器件内部的光场分布，从而实现器件性能的提升。本文首先探究了局域表面等离子体共振效应在光电探测器中的应用。由于局域表面等离子体共振效应，贵金属纳米颗粒能够将电磁场限制在纳米尺寸范围内，通过将贵金属纳米颗粒和有机活性层耦合，可以更高效的将贵金属周围的光能提取利用，从而实现了光电流22倍的增强。同时，本文通过COMSOL模拟计算，分析了器件内部的电场分布情况。本文进一步探索了不同的银纳米立方体的尺寸，密度和局域表面等离子体共振模式对光电探测器性能的影响，通过实验数据和COMSOL计算相结合，优化了器件的性能，系统的分析了器件的增强机制。为了实现特定波长的选择性探测，本文研究了法布里珀罗腔在光电探测器中的应用。由于光在法布里珀罗腔内的共振效应，特定波长的光场被局域在腔体内，从而导致了光电探测器光电流的10倍增强。通过调整法布里珀罗腔的腔体厚度，腔体的共振波长也随之改变,器件的EQE峰也随着腔体厚度的增加从可见光红移到近红外，并且在860 nm处实现了20 nm的窄带探测。另外，针对近红外光在生物医学应用上的优势，本论文还搭建了脉搏测试系统，将该近红外光电探测器应用到脉搏信号的探测中。综上，本论文通过将光学谐振器耦合到有机近红外光电探测器中，使得器件性能的得到了提升，窄带探测的功能得到了实现。这为进一步发展有机光电探测器的结构以及其实际应用提供了有效的方案，同时促进了光子学和光电学的交叉领域的发展。
Photodetectors based on organic semiconductor materials have the advantages in mechanical softness, solution processing, easy large-scale production, adjustable band gap, etc., which can make up for the shortages of traditional inorganic photodetectors in the application of flexible printable electronic devices. Due to the significance of near-infrared photodetectors in the fields of medical application, optical fiber communication, quality inspection, biological imaging and unmanned aerial vehicle, many researches have been carried out to widen the spectral response of organic photodetectors to the near-infrared region via adjusting the molecules structures of organic materials. However, organic photodetectors still have many disadvantages, such as low optoelectronic response, low stability and nonselective detection, which limit their further commercial applications. To address those challenges, novel device structures were designed in this thesis. Through coupling optical resonators into organic photodetector, the optical field intensity and distribution in the devices was adjusted in the active layer, realizing the photocurrent enhancement and narrowband detection. In this thesis, we studied the localized surface plasmon resonance (LSPR) effect and applied it in photodetector. Due to the LSPR effect, noble metal nanoparticles can confine the electromagnetic field within a nanoscale volume. By coupling noble metal nanoparticles with the organic active layer, the high-intensity light energy around the noble metal nanoparticles can be extracted and utilized more efficiently, resulting in the photocurrent enhancement with 22-fold. To explain the work mechanism, the electric field distribution in the device was analyzed via COMSOL simulation. In additional, this thesis systemically studied the influence of nanoparticles` size, density and LSPR modes on the device performance. Through the combination of experimental data and simulation, the performance of the device is optimized.In order to achieve the narrowband detection, this paper studied a photodiode coupled with Fabry-perot cavity. Due to the resonance effect in the Fabry-perot cavity, electromagnetic field at specific wavelength was confined in the cavity, resulting in a 10-fold enhancement in photocurrent. Through adjusting the thickness of cavity, the resonance wavelength of the cavity was also changed. Therefore, the corresponding EQE peak also red shifts from ultraviolet light to near infrared with the increase of the cavity thickness, and the narrowband peaks even achieved a FWHM of 20 nm at 860 nm. Therefore, the cavity enhanced photodetector realized the adjustable narrowband detection. sIn conclusion, optical resonators could be applied to enhance the device performance realize the specific function via adjusting the electromagnetic field intensity and distribution in device. Thus, this thesis provided effective strategies for photodetector structure design, and promotes the development of the intersection of photonics and optoelectronics.
