EL07.03.04 Universality of Photoluminescence Lifetimes in Slowly Emitting Silicon Quantum Dots

Silicon quantum dots (SiQDs) are a class of light-emitting materials with very low inherent toxicity and broad spectral tunability. SiQDs are being developed for several decades and a wide range of synthesis techniques are available now. Generally speaking, several modes of light emission from SiQDs have been reported in the literature, covering an extremely wide range of photoluminescence lifetimes from hundreds of microseconds to ten nanoseconds. In this contribution, we focus on the "traditional", first-reported mode of light emission featuring slow (tens to hundreds of microseconds) emission tunable from the red to the near infrared spectral range, originating in the lowest excited transition of the quantum-confined states in the QD. Using our characterization of SiQD samples prepared by various techniques and a wide compilation of literature data, we observe striking similarities in the lifetimes of differently prepared samples and propose that all these fabrication techniques yield SiQDs with fundamentally similar properties. Our analysis provides us with a tool for the determination of radiative and slow non-radiative lifetimes of these samples, which is, unlike complicated measurements of internal quantum efficiency yielding the same quantity, extremely easy to apply. We also differentiate between fast and slow non-radiative pathways and discuss the importance of the radiative and both the fast and the slow non-radiative pathways in the assessment of the overall emission properties of slowly emitting SiQDs.