Reduced Optical Gain Threshold by Carrier Multiplication in Semiconductor Perovskite Nanocrystals

TL;DR

This study demonstrates that carrier multiplication in semiconductor perovskite nanocrystals significantly reduces the optical gain threshold, enhancing the efficiency of laser operation.

Contribution

The paper reports the synthesis of FAPbI3/NdF3 nanocrystals exhibiting high carrier multiplication efficiency, leading to a two-fold reduction in optical gain threshold compared to traditional excitation methods.

Findings

Carrier multiplication efficiency of ~25.7% at 355 nm excitation.

Reduction of optical gain threshold by approximately 50%.

Potential for improved continuous-wave lasing with less optical pumping.

Abstract

Carrier multiplication (CM) describes a strong charge-carrier interaction process in semiconductor colloidal nanocrystals (NCs), wherein two band-edge excitons are simultaneously created by an absorbed photon with at least twice the bandgap energy (2 Eg). While being fundamentally intriguing, it has been exclusively utilized to enhance the light-to-electricity conversion efficiencies in the photodetector and solar-cell devices. In this report, we have synthesized the core/shell perovskite FAPbI3/NdF3 NCs with a biexciton recombination lifetime of ~3.9 ns, and demonstrated that a CM efficiency of ~25.7% can be achieved under the ~355 nm laser excitation (~2.21 Eg). This CM occurrence leads to a two-fold reduction in the optical gain threshold, as compared to that obtained under the ~640 nm laser excitation (~1.23 Eg). When combined with the single-exciton and zero-threshold optical gain schemes previously developed for semiconductor colloidal NCs, the CM effect introduced here would further mitigate the optical-pumping requirement for the routine operation of continuous-wave lasing.