| 초록 |
High oscillator strength and tunable band gap of colloidal quantum dots (CQDs) enable us to utilize this novel material as lasing gain medium. Despite successful demonstrations on optically-pumped lasing, electrically-driven lasing of CQDs has never been realized so far, mainly due to the ultrafast gain depletion by Auger recombination. Here, we realize for the first time the optical gain of CQDs by "direct" electrical current, which is a critical milestone toward solution-processed laser diodes. An important innovation in this work is a new class of type-I II-VI CQDs with smoothened confinement potential. This specially-designed electronic structure suppresses the Auger recombination of multiexcitons by controlling initial and final electronic states involving the Auger process. In a "current-focusing" device that reaches high direct current densities up to 18 A/cm2, we accomplished the optical gain of bans-edge 1S states that is manifested by clear 1P state emission. |
