Improved Brightness and Color Tunability of Solution-Processed Silicon Quantum Dot Light-Emitting Diodes
Hiroyuki Yamada, Noriyuki Saitoh, Batu Ghosh, Yoshitake Masuda, Noriko Yoshizawa, Naoto Shirahata
Abstract
Herein, an enhanced electroluminescence (EL) performance of solution-processed silicon quantum dot light-emitting diodes (Si-QLEDs) is demonstrated. We prepared colloidal inks of silicon quantum dots (Si QDs) for light-emissive layers using thermal hydrosilylation of 1-decene on their hydrogen-terminated surfaces, which are provided by thermal disproportionation of triethoxysilane hydrolyzed at pH 3 and subsequent hydrofluoric etching. The QLEDs have an inverted device architecture with multilayers. The electroluminescence color can be tailored from deep red to the yellow spectral region by synthetically varying the QD size. The peak values of the external quantum efficiency and luminance are 3.36% and 1,640 cd/m2 for 755 nm EL, 1.15% and 2268 cd/m2 for 722 nm EL, 1.18% and 10,884 cd/m2 for 670 nm EL, 0.89% and 19,934 cd/m2 for 635 nm EL, and 0.12% and 6586 cd/m2 for 590 nm EL, respectively. Due to the advantages of the inverted device structure, the QLEDs do not exhibit parasitic emissions from the neighboring compositional layers and have high device stability over a wide range of device operation voltages. The structural origin for the improved device performance is discussed using cross-sectional scanning transmission electron microscopy observations.