New Method Unveils the Hidden Lives of Quantum Dots

Quantum dots (QDs) are nanosized semiconductor particles crucial for future optoelectronics, yet understanding their complex energy states remains a challenge. Specifically, 'multiexcitons'—states where multiple electron-hole pairs exist simultaneously—often undergo rapid non-radiative decay, making them difficult to capture. Previous methods relying on single-particle studies frequently struggled with noise and obscured data.

To solve this, researchers have introduced a new method: spectrally resolved time-gated heralded spectroscopy. By analysing ensembles of CdSe/CdS core/shell quantum dots, this technique provides high photon counts and significantly reduced noise. The study successfully extracted binding energies for biexcitons, revealing a transition from attractive to repulsive interactions depending on the dot's size.

Furthermore, the team resolved open questions regarding triexcitons—states involving three excitons. They accurately determined lifetimes and spectral pathways that were previously hidden. This robust approach offers a clearer window into the many-body interactions within quantum dots, promising rapid characterisation for various other QD systems.