基于相干双光子吸收的有机/聚合物电池光伏性能研究

Since the near infrared (NIR) light has very deep biological tissue penetration depth, NIR photovoltaic cells is a less invasion method for supplying power to the implant medical devices. The excitation light source of two-photon absorption (TPA) is localized at NIR band. Combination coherent TPA mechanism with the polymer photovoltaic cells is a novel idea for NIR photoelectric conversion. Till now, this kind of research has been still rare. This proposal will employ the rigid planar conjugated polymer with large TPA coefficient as well as excellent optoelectronic property as donor in active layer, PC71BM as receptor, and polyethylene terephthalate / indium tin oxide (PET/ITO) as a flexible substrate, to prepare the coherent TPA polymer photovoltaic devices. By using a variety of morphology optimizing methods and device interfacial engineering, the phase separation of the active layer film and the carrier transport characteristic will be improved. Moreover, the minimized space charge accumulation and the carrier transport balance in devices will further enhance the performance of the TPA based photovoltaic cells powered by femtosecond pulse laser. Considering the merits of the TPA based polymer cells such as flexibility and good biological compatibility, and the advantages of the TPA NIR excitation source, such as the deeper tissue penetration depth, the lower photon-induced damage, three-dimensional positioning charging, the development of coherent TPA based organic photovoltaic cells will offer a reliable, safe and efficient power supply for the implant medical devices.

由于近红外光的生物组织穿透性，开发高效近红外光电转换电池器件对植入式医疗设备无线经皮充电有重大的实际意义。双光子吸收的激发光源位于近红外波段，把相干双光子吸收的光吸收机制引入到聚合物电池是一种全新的近红外光电转换概念，目前该方面的研究工作还很少。本项目拟采用兼具大的双光子吸收系数和光电特性的刚性平面共轭聚合物为活性层给体，PC71BM为受体， PET/ITO衬底，制备高效相干双光子吸收的柔性薄膜电池。通过采用形貌优化和界面修饰等手段，研究优化活性层两相分离，改善界面性能，减小活性层内部的空间电荷积累以及平衡载流子输运的内在机理和一般规律，建立在飞秒激光激发下相干双光子吸收聚合物电池器件光电转换的微观物理模型。由于聚合物电池器件柔性和良好的生物兼容性，双光子激发光源的更深组织穿透深度、更低的光致损伤以及三维空间定位充电等优势，双光子吸收电池器件将为植入式医疗装置寻找到一种安全可靠的供电方式。

把相干双光子吸收机制引入到聚合物电池是一种全新的近红外光电转换概念，本项目从材料筛选和设计、器件制备及优化等方面进行协同研究，实现了基于相干双光子吸收的近红外光电转换器件。具体研究成果如下：利用Z扫描技术研究了几种高效聚合物电池给受体材料，发现其双光子吸收截面和共轭链长、给受体单元排列方式、薄膜堆积形貌有关；基于筛选的大双光子吸收截面的聚合物和富勒烯制备本体异质结倒装电池器件，其光电流与入射功率的平方成正比，验证了双光子响应特性，并通过活性层形貌和界面工程优化其光电转换效率；利用时间分辨光谱技术研究载流子复合动力学，发现通过薄膜形貌调控可以有效抑制缺陷和俄歇复合，提高器件效率；采用合适的氧化物阳极和阴极修饰层，同样可以有效抑制电荷的复合损失。研究结果对进一步提高双光子吸收电池器件提供了可行的理论依据和方法。另外，本项目也基于高双光子吸收截面的共轭高分子作为能量供体、红光发光分子和合适的光敏剂作为能量受体，基于能量传递原理开发了一种双光子成像和光动力治疗的多功能纳米光敏剂。由于聚合物良好的生物兼容性，双光子激发光源的更深组织穿透深度、更低的光致损伤以及三维空间定位充电等优势，基于双光子吸收的光电转换器件是未来植入式医疗装置的一种安全可靠的供电方式，项目的研究结果为高效双光子吸收电池器件的实现提供了重要的参考意义。