Substituted Di(thio)pyranylidenes and their CT Complexes with C60 for Organic Near-Infrared Detectors

近红外光的检测在过去的几十年中由于在工业、科学、医学和军事中的新兴应用而引起了极大的兴趣。有机光电探测器（OPD）具有克服无机光电探测器在材料加工和集成方面的局限性的潜力，并且将近红外光的无滤波检测与有机电子器件的优点（例如低成本、低功耗、低成本）相结合。OPD的质量取决于具有高光电流和低暗电流的有效光捕获过程，以及工作光谱中的高光谱选择性。然而，传统的近红外吸收材料往往缺少这些先决条件。为了克服这一基于材料的问题，德累斯顿应用物理和光子材料综合中心（IAPP）的Siegmund等人提出了一种新的有前途的方法。这种方法利用了在一种新型的光学微腔器件结构中的电子供给和接受材料之间的界面处形成的分子间CT态。结果表明，CT吸收的特性，如弱强度，宽和灵敏度在长波长，可以用于光学微腔光电探测器，以产生高光谱选择性高达36 nm和波长可调谐的光谱响应高达1550 nm。C60用作真空沉积的OSC和OPD的标准受体选择。然而，供体组分的选择是根据其容易与C60形成CT复合物的能力，从而导致宽的和远红移的CT吸收-这种效应通常在OSC中是不期望的，但在新的腔概念中明确利用。在他的研究中，Siegmund使用了两种具有上述性质的供体材料，即酞菁锌（ZnPc）和2，2 '，6，6'-四苯基-4，4-二苯并噻吩（2，2 '，6，6'-tetraphenyl-4，4-tetraphenyl-4，4 '-二吡喃亚基（TPDP）。已知这两种材料在与C60共混时出现新的红移吸收。TPDP和ZnPc的CT吸收分别达到1550 nm和1100 nm。这些结果确定TPDP作为一个有前途的施主材料的CT为基础的光电探测器。通过进一步官能化分子结构，可以改变吸收特性，特别是有利于更强和更多红移的CT吸收。到目前为止，只有很少的尝试已经作出了合成TPDP家族的其他成员。本论文的重点是合成和表征与TPDP结构类似的四芳基取代二吡喃亚基化合物，并着重研究其在OPD中的应用。这包括通过循环伏安法（CV），差示扫描量热法（DSC）和密度泛函理论（DFT）计算的研究。此外，在真空沉积的OSC中测试了目标材料，通过外量子效率（EQE）光谱和电流-电压（IV）曲线表征了其光电特性。

Detection of NIR light has attracted significant interest in the last few decades due to the emerging applications in industry, science, medicine and military. Notable examples are optical wireless communication, emerging biomedical imaging, environmental monitoring and night vision.An organic photodetector (OPD) has the potential to overcome the limits of inorganic photodetectors concerning material processing and integration and combine filterless detection of NIR light with the advantages of organic electronic devices such as low-cost, lightweight and environmental friendliness.The quality of the OPDs depends on an efficient light harvesting process with high photocurrent and low dark current, and on a high spectral selectivity in the operation spectrum. However, conventional NIR absorber materials are often missing those prerequisites.Seeking to overcome this material-based problem, a new and promising approach was proposed by Siegmund et al. from the Dresden Integrated Centre for Applied Physics and Photonic Materials (IAPP). This approach exploits the intermolecular CT states formed at the interface between electron donating and accepting materials in a novel type of optical micro-cavity device architecture. It was demonstrated that the characteristic features of the CT absorption, such as weak intensity, broadness and sensitivity at long wavelengths, can be used in an optical micro-cavity photodetector to yield a high spectral selectivity up to 36 nm and wavelength tuneable spectral responses up to 1550 nm. C60 was used as a standard acceptor choice for vacuum-deposited OSCs and OPDs. The donor component, however, was chosen according to its ability to readily form a CT complex with C60 leading to a broad and far red-shifted CT absorption - an effect that is usually undesired in OSCs, but explicitly utilized in the new cavity concept.In his study, Siegmund employs two donor materials with the aforementioned properties, namely zinc phthalocyanine (ZnPc) and 2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (TPDP). It is known for both materials that a new red-shifted absorption appears upon blending with C60. The comparison of the devices made with TPDP and ZnPc shows a CT absorption up to 1550~nm for TPDP and up to 1100~nm for ZnPc. Those results identify TPDP as a promising donor material for the CT-based photodetector. By further functionalizing the molecular structure, it is possible to change the absorption characteristics, in particular in favor for a stronger and more red-shifted CT absorption. Up to now, only few attempts have been made to synthesize other members of the TPDP family. Moreover, there was no emphasis on their prospective application in OPDs.The thesis focuses on the synthesis and characterization of materials with a similar structure to TPDP (here referred to as tetraaryl-substituted dipyranylidenes), with a strong emphasis on their application in OPDs. This includes investigations via cyclic voltammetry (CV), differential scanning calorimetry (DSC) and density functional theory (DFT) calculations. Furthermore, the target materials were tested in vacuum-deposited OSCs, of which the optoelectrical properties were characterized via external quantum efficiency (EQE) spectra and current-voltage (IV) curves.