Direct evidence for photoionization in CdTe nanocrystals embedded in trioctylphosphine oxide

The existence of photoionization processes in nanocrystals has been experim entally proved for the first time by measuring the temperature dependences of the photocurrent and the photoluminescence of CdTe nanocrystals embedded in trioctylphosphine oxide (TOPO), the phase transition of the matrix TOPO from amorphous solid to liquid makes the diffusion length of the emitted;c arriers outside the nanocrystals increase abruptly, resulting in a steep ri se in both the photocurrent and the photoluminescence. The photoionization has turned out to be fundamentally important for the optical properties of nanocrystals.