Photon antibunching in a cluster of giant CdSe/CdS nanocrystals

Bihu Lv,Huichao Zhang,Jiayu Zhang,Chunfeng Zhang,Lipeng Wang,Min Xiao,Xiaoyong Wang

doi:10.1038/s41467-018-03971-w

Abstract

When closely packed into a high-density film, semiconductor nanocrystals (NCs) can interact with each other to yield collective optical behaviours, which are normally difficult to characterize due to the ensemble average effect. Here we synthesized semiconductor NC clusters and performed single-particle spectroscopic measurements to probe the electronic couplings of several giant CdSe/CdS NCs contained in one cluster with nanometer-scale separations. Such a single cluster exhibits multiple emission peaks at the cryogenic temperature with nearly identical photoluminescence decay dynamics, suggesting that the Förster-type energy transfer does not occur among the composing NCs. Surprisingly, strong photon antibunching is still observed from a single cluster, which can be attributed to the Auger annihilation of photo-excited excitons from different NCs. The isolation of several nearby NCs interacting with the above novel mechanism has marked a solid progress towards a full understanding and an efficient control of the operation parameters in NC-based optoelectronic devices.

Highlights

When closely packed into a high-density film, semiconductor nanocrystals (NCs) can interact with each other to yield collective optical behaviours, which are normally difficult to characterize due to the ensemble average effect
Compared to individual giant CdSe/CdS NCs (gNCs) at room temperature, such a single gNC cluster possesses a relatively larger absorption cross section, but otherwise exhibits very similar optical properties in terms of nonblinking PL, long single-exponential lifetime and strong photon antibunching effect. This quantum nature of single-photon emission is still kept for a single gNCC at the cryogenic temperature, its broad PL spectrum measured at room temperature is divided into multiple emission peaks with nearly identical PL decay dynamics to exclude the Förster energy transfer (ET) interactions among the composing gNCs
The bandedge absorption and emission peaks of ensemble gNCCs are located at 610 nm and 640 nm (Fig. 1g), respectively, while the PL decay curve measured at the emission peak could be roughly fitted with a single-exponential lifetime of 93.1 ns (Fig. 1h)

Summary

Introduction

When closely packed into a high-density film, semiconductor nanocrystals (NCs) can interact with each other to yield collective optical behaviours, which are normally difficult to characterize due to the ensemble average effect. 50 100 150 200 Time (ns) intensities measured as a function of the laser excitation powers for a single gNCC and a single gNC with the same CdS shell thickness of 20 MLs. These two sets of data points were normalized according to their respective maximum PL intensities obtained within the displayed laser power range.

Results

Conclusion