Highly-directional, highly-efficient solution-processed light-emitting diodes of all-face-down oriented colloidal quantum wells

Hamed Dehghanpour Baruj; Iklim Yurdakul; Betul Canimkurbey; Ahmet Tarik Isik; Farzan Shabani; Savas Delikanli; Sushant Shendre; Onur Erdem; Furkan Isik; Hilmi Volkan Demir

arXiv · 2201.08733

Highly-directional, highly-efficient solution-processed light-emitting diodes of all-face-down oriented colloidal quantum wells

Hamed Dehghanpour Baruj·Iklim Yurdakul·Betul Canimkurbey·Ahmet Tarik Isik·Farzan Shabani·Savas Delikanli·Sushant Shendre·Onur Erdem·Furkan Isik·Hilmi Volkan Demir

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Abstract

Semiconductor colloidal quantum wells (CQWs) make an exciting quasi-2D class of nanocrystals thanks to their unique properties including their highly anisotropic optical transition dipole moment (TDM). Thus, employing a film of CQWs with face-down orientation as an emissive layer (EML) in an electroluminescent device is expected to substantially boost photon outcoupling efficiency. Here, we show all-solution-processed colloidal quantum well light-emitting diodes (CQW-LEDs) using a single all-face-down oriented self-assembled monolayer (SAM) film of CQWs that enables a high level of in-plane (IP) TDMs of 92%. This SAM film significantly enhances the outcoupling efficiency from 22% (of standard randomly-oriented emitters) to 34% (of face-down oriented emitters) and charge injection efficiency. This SAM-CQW-LED architecture enables a record high level of external quantum efficiency of 18.1% for the solution-processed type of CQW-LEDs, putting their efficiency performance on par with the hybrid organic-inorganic evaporation-based CQW-LEDs and all other best solution-processed LEDs. In addition, this architecture provides a high maximum brightness of 19,800 cd/m2 with a long operational lifetime of 247 h at 100 cd/m2 along with saturated deep-red emission (651 nm). These findings indicate the effectiveness of oriented self-assembly of CQWs as electrically-driven emissive layers in improving outcoupling and external quantum efficiencies in the CQW-LEDs.

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Hamed Dehghanpour Baruj, Iklim Yurdakul, Betul Canimkurbey, Ahmet Tarik Isik, Farzan Shabani, Savas Delikanli, Sushant Shendre, Onur Erdem, Furkan Isik, Hilmi Volkan Demir. 2022-01-21. Highly-directional, highly-efficient solution-processed light-emitting diodes of all-face-down oriented colloidal quantum wells. https://arxiv.org/abs/2201.08733

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