Ultra-Fast Optical Characterization of Long-Lived Holes in CdSe Quantum Shells

A long-lived spin polarized charge or exciton is the most critical material property for the use of polarized spins in energy and electronics applications. Here, we use time resolved circular dichroism (TRCD) spectroscopy to study photo-induced spin polarization and dynamics of 2-dimensional holes in CdSe quantum shells. The TRCD measurements produces transient spectra that can be used to distinguish between the heavy and light hole species, while simultaneously collecting kinetic information. We also studied TRCD of the CdSe solutions in a magnetic field and modeled the field-dependent dynamics to extract the electron, heavy hole, and light hole g-factors. We found that the 2-dimensional holes have a long spin-lattice and spin-spin dephasing time of over 7 ns, while the electron spin dephasing occurs on the order of 50 ps.