Efficient carrier multiplication in InP nanoparticles is reported; ultrafast transient absorption measurements at the band edge were used to determine the number of excitons per photoexcited nanoparticle for a range of both excitation fluences and photon energies. At photon energies greater than $2.1\pm 0.2$ times the band gap, an average of more than 1 exciton per photoexcited nanoparticle was found even in the limit of vanishing fluence. The average number of excitons generated by an absorbed photon was measured to be $1.18\pm 0.03$ for excitation photons with energies 2.6 times the band gap.

• Received 26 October 2009

DOI:https://doi.org/10.1103/PhysRevB.81.081303