新型窄带隙、宽光谱光伏响应聚合物材料的设计、合成及其光探测性能研究

In recent years, organic/polymer photodetectors have drawn much attention because of its potential applications in civil/military use and academic research. However, new materials for multi-color photodetectors with broad spectral response were seldom been reported recently. A key limiting factor for narrow band-gap polymers blames to the extremely low LUMO energy levels which will lead to the mismatching of polymers with acceptors (such as PCBM). In this project, we focus on the design of new D-A polymers with narrow band-gaps by increasing the HOMO energy levels of polymers while controlling the LUMO energy levels at a suitable level. And the strong D-A effect will lead to a strong ICT absorption in the long wavelength range. Meanwhile, the non-covalent coulomb interactions are good for a more planar molecular backbone and a better π-π interaction, which may contribute to a higher mobility. As to the device structure, exciton blocking layers will be applied to the device, trying to reduce the dark current and increase the detectivities. Through the study of this project, we are expected to develop a series of new narrow band-gap polymers which will be applied to the polymer photodetectors with high detectivities and broad spectral response.

有机/聚合物光电探测器由于其在民用、军用以及科学研究等方面的潜在应用而得到了广泛的研究，但是对于具有多色响应的宽光谱响应聚合物光电探测器新材料的报道则较少。一个重要的原因在于宽光谱吸收窄带隙聚合物的LUMO能级易于调控过低而与受体材料不匹配。本项目中，我们采用控制窄带隙聚合物的LUMO能级，通过增加其HOMO能级的方法来得到能级匹配同时具有宽光谱吸收的窄带隙给体材料。材料设计上，通过设计新型的强给电子片段来构建强的给受体共轭聚合物，利用分子内强的D-A作用来得到位于长波方向的吸收峰；同时结合分子内的非键弱相互作用来增加分子骨架的平面性和π-π相互作用，以提高材料的迁移率；器件结构上，选择能级合适的激子阻隔层，降低暗电流，提高器件的探测率。本项目结合材料设计与器件优化，有望得到一批具有较高探测率以及宽光谱光伏响应的聚合物光电探测器材料及器件,并为宽光谱响应聚合物材料的设计提供值得借鉴的思路。

新型窄带隙聚合物由于其宽的吸收光谱与高的太阳光捕获能力在光电转换器件中具有广泛的应用前景。在本项目中，我们基于对新型窄带隙宽光谱聚合物的设计思路，得到了一批窄带隙甚至超窄带隙（光学带隙=1.00 eV左右）的聚合物材料，并研究其在有机光伏电池和光电探测等光电转换器件中的性能。具体而言，通过在分子内构建非共价键弱相互作用，增强分子骨架的共轭平面与分子内的电荷转移，可以利用强的电荷转移峰得到光谱和带隙可调的共轭聚合物材料，并极大地拓宽对太阳光的响应范围。本项目的研究为新型窄带隙共轭聚合物的设计及其在有机光伏电池和光电探测器件中的研究提供了一些值得借鉴的思路。