Colloidal CdSe/CdS Quantum Dots as Bright and Tunable Single-Photon Emitters

Single-photon emitters are a key component of quantum technology, and often based on epitaxial quantum dots, NV-centers in diamond, or strongly attenuated lasers. However, colloidal quantum dots are becoming a viable, solution-processed alternative. For instance, in contrast with epitaxial quantum dots, they can operate at room temperature, and their emission can be tuned to any desired wavelength by simply controlling the composition and size of the quantum dots. In addition, their inherent nanoscale dimensions allows for miniaturization, and on-chip implementation.<br/>In this talk, I will discuss how to synthesize highly fluorescent CdSe/CdS colloidal quantum dots that show (nearly) no intermittence.¹ Next, as these quantum dots have intrinsic fluorescence lifetimes that extend beyond 100 nanosecond, I will show how one can increase the emission rate by charging them with up to 20 electrons, which increases the radiative recombination rate, while at the same time the nonradiative Auger rate remains suppressed due to the proper choice of quantum dots core and shell dimensions.² Finally, I will demonstrate that the single-photon emission can be improved by spectrally filtering out the biexciton emission, which, due to the unique features of our quantum dots, can be performed at room temperature due to the exceptionally large blue shift of the biexciton emission.³In particular, this blue shift is achieved by exploiting strain and piezoelectric fields in our CdSe/CdS pure-phase wurtzite quantum dots, which is know to increase the electron-hole separation and exciton-exciton repulsive interactions, especially for quantum dots with a large CdSe core.^4,5<br/><br/>[1] S. Christodoulou et al., <i>J. Mater. Chem. C</i> <b>2014</b>, <i>2</i>, 3439<br/>[2] S. Morozov et al., <i>Sci. Adv.</i> <b>2020</b>, <i>6</i>, eabb1821<br/>[3] S. Morozov et al., <i>ArXiv211109090 Cond-Mat Physicsphysics</i> <b>2021</b><br/>[4] S. Christodoulou et al., <i>Nat. Commun.<b> </b></i><b>2015</b><i>, 6</i>, 7905<br/>[5] A. Polovitsyn et al., <i>ACS Photon. </i><b>2018</b>, <i>5</i>, 4561-4568