Record High External Quantum Efficiency of 19.2% Achieved in Light‐Emitting Diodes of Colloidal Quantum Wells Enabled by Hot‐Injection Shell Growth. Issue 8 (23rd December 2019)

• Record Type: Journal Article
• Authors: Liu, Baiquan; Altintas, Yemliha; Wang, Lin; Shendre, Sushant; Sharma, Manoj; Sun, Handong; Mutlugun, Evren; Demir, Hilmi Volkan
• Is Part Of: Advanced materials. Volume 32:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-12-23
• Subjects: colloidal quantum wells -- core/shell structures -- hot injection -- light‐emitting diodes -- nanoplatelets; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.201905824
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: 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/Cd0.25 Zn0.75 S 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. Abstract : Light‐emitting diodes based on colloidal quantum wells (CQWs) exhibit an external quantum efficiency close to the theoretical maximum of 20%. The core/hot‐injection shell CQWs show a near‐unity photoluminescence quantum yield, retaining 87% in film even after five times cleaning. A luminance of 23 490 cd m −2, along with an extremely stable color point of saturated red electroluminescence is achieved.