Liu, BaiquanAltintas, YemlihaWang, LinShendre, SushantSharma, ManojSun, HandongDemir, Hilmi Volkan2025-09-252025-09-2520200935-96481521-4095https://doi.org/10.1002/adma.201905824https://hdl.handle.net/20.500.12573/4550Demir, Hilmi Volkan/0000-0003-1793-112X; Mutlugun, Evren/0000-0003-3715-5594; Sun, Handong/0000-0002-2261-7103; Sharma, Manoj/0000-0001-5215-9740; Liu, Baiquan/0000-0001-9375-7683;Colloidal quantum wells (CQWs) are regarded as a highly promising class of optoelectronic materials, thanks to their unique excitonic characteristics of high extinction coefficients and ultranarrow emission bandwidths. Although the exploration of CQWs in light-emitting diodes (LEDs) is impressive, the performance of CQW-LEDs lags far behind other types of soft-material LEDs (e.g., organic LEDs, colloidal-quantum-dot LEDs, and perovskite LEDs). Herein, high-efficiency CQW-LEDs reaching close to the theoretical limit are reported. A key factor for this high performance is the exploitation of hot-injection shell (HIS) growth of CQWs, which enables a near-unity photoluminescence quantum yield (PLQY), reduces nonradiative channels, ensures smooth films, and enhances the stability. Remarkably, the PLQY remains 95% in solution and 87% in film despite rigorous cleaning. Through systematically understanding their shape-, composition-, and device-engineering, the CQW-LEDs using CdSe/Cd0.25Zn0.75S core/HIS CQWs exhibit a maximum external quantum efficiency of 19.2%. Additionally, a high luminance of 23 490 cd m(-2), extremely saturated red color with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.715, 0.283), and stable emission are obtained. The findings indicate that HIS-grown CQWs enable high-performance solution-processed LEDs, which may pave the path for future CQW-based display and lighting technologies.eninfo:eu-repo/semantics/closedAccessColloidal Quantum WellsCoreShell StructuresHot InjectionLight-Emitting DiodesNanoplateletsArticle10.1002/adma.2019058242-s2.0-85076889973