Room Temperature Lasing in Micro-Rings of Blended Core/Shell Quantum Dots

Colloidal quantum dots (QDs) are nanoscale semiconductor particles with unique optical and electronic properties, widely used in optoelectronic fields as gain materials. Particularly in micro-lasers, the lasing investigation of blended core/shell QDs plays an important role in improving lasing performance and exciton dynamics. Here, we demonstrate room-temperature photonic lasing in blended QD micro-rings and reveal the mechanism of population inversion. High-quality micro-rings of red and green colloidal core/shell QDs and their blend are fabricated by utilizing the solution self-assembled patterning method. Steady-state and timeresolved spectral characterization illustrate the lasing of blended QD rings arising from the exciton transition of the 2S state, while the lasing of pure red and green QD rings with the 1S exciton transition. In blended QD rings, Förster resonance energy transfer (FRET) from green QDs to red QDs induces exciton redistribution and promotes exciton accumulation in the 2S state of red QDs rather than the 1S state, leading to population inversion and lasing emission. Our study of lasing behaviors and mechanisms for blended colloidal QD micro-rings paves a promising avenue toward further developing on-chip integrated QD lasing sources and optoelectronic devices.