Altintas, YemlihaGungor, KivancGao, YuanSak, MustafaQuliyeva, UlviyyaBappi, GolamDemir, Hilmi Volkan2025-09-252025-09-2520191936-08511936-086Xhttps://doi.org/10.1021/acsnano.9b04967https://hdl.handle.net/20.500.12573/3899Sargent, Edward/0000-0003-0396-6495; Mutlugun, Evren/0000-0003-3715-5594; Demir, Hilmi Volkan/0000-0003-1793-112XAs an attractive materials system for high- Record-low optical gain threshold in giant-shell COWs performance optoelectronics, colloidal nanoplatelets (NPLs) benefit from atomic-level precision in thickness, minimizing emission inhomogeneous broadening. Much progress has been made to enhance their photoluminescence quantum yield (PLQY) and photostability. However, to date, layer-by-layer growth of shells at room temperature has resulted in defects that limit PLQY and thus curtail the 0.2 performance of NPLs as an optical gain medium. Here, we introduce a hot-injection method growing giant alloyed shells using an approach that reduces core/shell lattice mismatch and suppresses Auger recombination. Near-unity PLQY is achieved with a narrow full-width-at-half-maximum (20 nm), accompanied by emission tunability (from 610 to 650 nm). The biexciton lifetime exceeds 1 ns, an order of magnitude longer than in conventional colloidal quantum dots (CQDs). Reduced Auger recombination enables record-low amplified spontaneous emission threshold of 2.4 mu J cm(-2) under one-photon pumping. This is lower by a factor of 2.5 than the best previously reported value in nanocrystals (6 /kJ cm(-2) for CdSe/CdS NPLs). Here, we also report single-mode lasing operation with a 0.55 mu J cm(-2) threshold under two-photoexcitation, which is also the best among nanocrystals (compared to 0.76 mu J cm(-2) from CdSe/CdS CQDs in the Fabry-Perot cavity). These findings indicate that hot-injection growth of thick alloyed shells makes ultrahigh performance NPLs.eninfo:eu-repo/semantics/closedAccessColloidal Quantum WellsNanoplateletsHot-Injection GrowthOptical GainSingle-Mode LasingVCSELArticle10.1021/acsnano.9b049672-s2.0-85072310080