Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP), Technische Universität Dresden, George-Bähr-Straße 1, Dresden 01062, Germany.
Institute for Applied Physics, Technische Universität Dresden, George-Bähr-Straße 1, Dresden 01062, Germany.
Nat Commun. 2017 Jun 5;8:15421. doi: 10.1038/ncomms15421.
Blending organic electron donors and acceptors yields intermolecular charge-transfer states with additional optical transitions below their optical gaps. In organic photovoltaic devices, such states play a crucial role and limit the operating voltage. Due to its extremely weak nature, direct intermolecular charge-transfer absorption often remains undetected and unused for photocurrent generation. Here, we use an optical microcavity to increase the typically negligible external quantum efficiency in the spectral region of charge-transfer absorption by more than 40 times, yielding values over 20%. We demonstrate narrowband detection with spectral widths down to 36 nm and resonance wavelengths between 810 and 1,550 nm, far below the optical gap of both donor and acceptor. The broad spectral tunability via a simple variation of the cavity thickness makes this innovative, flexible and potentially visibly transparent device principle highly suitable for integrated low-cost spectroscopic near-infrared photodetection.
将有机电子给体和受体混合会产生分子间电荷转移态，其光学跃迁低于光学间隙。在有机光伏器件中，这种状态起着至关重要的作用，并限制了工作电压。由于其极其微弱的性质，直接的分子间电荷转移吸收通常仍然未被检测到，也未用于光电流产生。在这里，我们使用光学微腔将通常可忽略不计的外部量子效率在电荷转移吸收的光谱区域中增加了 40 多倍，产生了超过 20%的值。我们演示了具有窄带宽检测的光谱宽度低至 36nm 和共振波长在 810 和 1550nm 之间，远低于供体和受体的光学间隙。通过简单改变腔厚来实现的宽光谱可调谐性使得这种创新、灵活且具有潜在可见透明度的器件原理非常适合集成低成本近红外光谱光电探测。
