Looking Inside a Working SiLED

• Published in: Nano letters 2013-08, Vol.13 (8), p.3539-3545
• Main Authors: Maier-Flaig, Florian, Kübel, Christian, Rinck, Julia, Bocksrocker, Tobias, Scherer, Torsten, Prang, Robby, Powell, Annie K, Ozin, Geoffrey A, Lemmer, U
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Degradation; Devices; Electric potential; Electroluminescence; Electronics; Exact sciences and technology; Failure analysis; Materials science; Molecular electronics, nanoelectronics; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Optoelectronic devices; Physics; Quantum dots; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transmission electron microscopy; Voltage; X-rays
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl400975u

In this study, we investigate for the first time morphological and compositional changes of silicon quantum dot (SiQD) light-emitting diodes (SiLEDs) upon device operation. By means of advanced transmission electron microscopy (TEM) analysis including energy filtered TEM (EFTEM) and energy dispersive X-ray (EDX) spectroscopy, we observe drastic morphological changes and degradation for SiLEDs operated under high applied voltage ultimately leading to device failure. However, SiLEDs built from size-separated SiQDs operating under normal conditions show no morphological and compositional changes and the biexponential loss in electroluminescence seems to be correlated to chemical and physical degradation of the SiQDs. By contrast, we found that, for SiLEDs fabricated from polydisperse SiQDs, device degradation is more pronounced with three main modes of failure contributing to the reduced overall lifetime compared to those prepared from size-separated SiQDs. With this newfound knowledge, it is possible to devise ways to increase the lifetimes of SiLEDs.