Colloidal Semiconductor Quantum Well Supraparticles as Low-Threshold and Photostable Microlasers

This study introduces and compares the lasing performance of micron-sized and sphere-shaped supraparticle (SP) lasers fabricated through bottom-up assembly of II-VI semiconductor colloidal quantum wells (CQWs) with their counterparts made of quantum dots (CQDs). CQWs consist of a 4-monolayers thick CdSe core and an 8-monolayers thick CdxZn1-xS shell with a nominal size of 14 x 15 x 4.2 nm, and CQDs of CdSxSe1-x/ZnS with 6 nm diameter. SPs are optically characterized with a 0.76 ns pulse laser (spot size: 2.88 x 10-7 cm2) at 532 nm, and emit in the 620-670 nm spectral range. Results show that CQW SPs have lasing thresholds twice as low (0.1-0.3 nJ) as CQD SPs (0.3-0.6 nJ), and stress tests using a constant 0.6 nJ optical pump energy demonstrate that CQW SPs withstand lasing emission for longer than CQD SPs. Lasing emission in CQW and CQD SPs under continuous operation yields half-lives of tau CQW SP approximate to 150 min and tau CQD SP approximate to 22 min, respectively. The half-life of CQW SPs is further extended to tau QW approximate to 385 min when optically pumped at 0.5 nJ. Such results compare favorably to those in the literature and highlight the performance of CdSe-based CQW SPs for laser applications.

CdSe-based colloidal quantum well supraparticles display a lower laser threshold than their quantum dot counterparts. When benchmarked against other state-of-the-art CdSe-based microlasers, these devices also score amongst the ones with the longest half-lives (between 102 and 103 min), and their degradation fluences (108-109 mJ cm-2) surpass those of all the CdSe-based quantum dot microlasers. image