Colloidal quantum dots are robust and flexible single photon emitters for
room-temperature applications, but their purity is strongly reduced at high
pump powers, due to multiexcitonic emission which cannot be easily filtered due
to the photo-luminescence spectral broadening at room temperature. Giant-shell
quantum dots feature a large blueshift of the biexciton spectrum due to
electron-hole wave function engineering and piezoelectric charge separation,
which can be exploited for spectral separation of the single exciton from the
multiexciton emission. Here, by spectral filtering, we show that we can recover
an excellent single-photon emission, with $g_2{(0)} < 0.05$ (resolution
limited), even at high pump powers above saturation of the exciton emission.
The bright and pure single-photon generation shown here has important
applications in quantum information technology and random-number generation.