Semiconductor colloidal quantum wells (CQWs) provide anisotropic emission behavior originating from their anisotropic optical transition dipole moments (TDMs). Here, solution‐processed colloidal quantum well light‐emitting diodes (CQW‐LEDs) of a single all‐face‐down oriented self‐assembled monolayer (SAM) film of CQWs that collectively enable a supreme level of IP TDMs at 92% in the ensemble emission are shown. This significantly enhances the outcoupling efficiency from 22% (of standard randomly‐oriented emitters) to 34% (of face‐down oriented emitters) in the LED. As a result, the external quantum efficiency reaches a record high level 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. This SAM‐CQW‐LED architecture allows for a high maximum brightness of 19,800 cd m−2 with a long operational lifetime of 247 h at 100 cd m−2 as well as a stable saturated deep‐red emission (651 nm) with a low turn‐on voltage of 1.7 eV at a current density of 1 mA cm−2 and a high J90 of 99.58 mA cm−2. These findings indicate the effectiveness of oriented self‐assembly of CQWs as an electrically‐driven emissive layer in improving outcoupling and external quantum efficiencies in the CQW‐LEDs.

We propose and demonstrate vertically-oriented self-assembly of colloidal quantum wells (CQWs) that allows for stacking CdSe/CdZnS core/shell CQWs in the film for the purposes of amplified spontaneous emission (ASE) and...

All‐Solution‐Processed Light‐Emitting Diodes In article number 2206582, Hilmi Volkan Demir and co‐workers propose all solution‐processed light‐emitting diodes (LEDs) of all face‐down oriented self‐assembled monolayer (SAM) films of colloidal quantum wells (CQWs) and demonstrate them with a high external quantum efficiency of 18.1% and a maximum brightness of 19,800 cd m−2. Here the SAM‐CQWs films boost the outcoupling efficiency from 22% of standard randomly‐oriented emitters to 34% in our LEDs.