Fu Xiangyu, Mehta Yash, Chen Yi-An, Lei Lei, Zhu Liping, Barange Nilesh, Dong Qi, Yin Shichen, Mendes Juliana, He Siliang, Gogusetti Renuka, Chang Chih-Hao, So Franky
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27606, USA.
Walker Department of Mechanical Engineering, University of Texas at Austin, Austin, TX, 78712, USA.
Adv Mater. 2021 Mar;33(9):e2006801. doi: 10.1002/adma.202006801. Epub 2021 Jan 29.
Light-emitting diodes (LEDs) with directional and polarized light emission have many photonic applications, and beam shaping of these devices is fundamentally challenging because they are Lambertian light sources. In this work, using organic and perovskite LEDs (PeLEDs) for demonstrations, by selectively diffracting the transverse electric (TE) waveguide mode while suppressing other optical modes in a nanostructured LED, the authors first demonstrate highly directional light emission from a full-area organic LED with a small divergence angle less than 3° and a TE to transverse magnetic (TM) polarization extinction ratio of 13. The highly selective diffraction of only the TE waveguide mode is possible due to the planarization of the device stack by thermal evaporation and solution processing. Using this strategy, directional and polarized emission from a perovskite LED having a current efficiency 2.6 times compared to the reference planar device is further demonstrated. This large enhancement in efficiency in the PeLED is attributed to a larger contribution from the TE waveguide mode resulting from the high refractive index in perovskite materials.
具有定向和偏振光发射特性的发光二极管（LED）有许多光子学应用，而对这些器件进行光束整形从根本上来说具有挑战性，因为它们是朗伯光源。在这项工作中，作者以有机发光二极管和钙钛矿发光二极管（PeLED）为例进行演示，通过在纳米结构的发光二极管中选择性地衍射横向电（TE）波导模式，同时抑制其他光学模式，首次展示了全区域有机发光二极管的高定向发光，其发散角小于3°，TE与横向磁（TM）偏振消光比为13。由于通过热蒸发和溶液处理实现了器件堆叠的平面化，仅对TE波导模式进行高选择性衍射成为可能。采用这种策略，进一步展示了与参考平面器件相比电流效率提高2.6倍的钙钛矿发光二极管的定向和偏振发射。钙钛矿发光二极管中这种效率的大幅提高归因于钙钛矿材料中的高折射率导致TE波导模式的贡献更大。
