Seed-mediated growth synthesis and tunable narrow-band luminescence of quaternary Ag-In-Ga-S alloyed nanocrystals.

Silver-based I-III-VI-type semiconductor nanocrystals have received extensive attention due to their narrow-band luminescence properties. Herein, we demonstrated a seed-mediated growth of quaternary Ag-In-Ga-S (AIGS) nanocrystals (NCs) with narrow-band luminescence. By conducting partial cation exchange with In3+ and Ga3+ based on Ag2S NCs and controlling the Ag/In feeding ratios (0.25 to 2) of Ag-In-S seeds as well as the inventory of 1-dodecanethiol, we achieved optimized luminescence performance in the synthesized AIGS NCs, characterized by a narrow full width at half maximum of less than 40 nm. Meanwhile, narrow-band luminescent AIGS NCs exhibit a tetragonal AgGaS2 crystal structure and a gradient alloy structure, rather than a core-shell structure. Most importantly, the kinetics decay curves of time-resolved photoluminescence and the ground state bleaching in transient absorption generally agree with each other regarding the lifetime of the second decay component, which indicates that the narrow-band luminescence is due to the slow radiative recombination between trapped electrons and trapped holes located at the edge of the conduction band and the deep silver-related trap states (e.g., silver vacancy), respectively. This study provides new insights into the correlation between the narrow-band luminescence properties and the structural characteristics of AIGS NCs.

Narrow-Bandwidth Blue-Emitting Ag-Ga-Zn-S Semiconductor Nanocrystals for Quantum-Dot Light-Emitting Diodes.

I-III-VI type semiconductor nanocrystals (NCs) have attracted considerable attention in the display field. Herein, we realized the synthesis of narrow-bandwidth blue-emitting Ag-Ga-Zn-S (AGZS) NCs via a facile one-pot method. Intriguingly, the Ag/Zn feeding ratio and Ag/Ga feeding ratio are crucial for the realization of narrow-bandwidth AGZS NCs. By choosing a Ag/Zn feeding ratio of 4:1 and Ag/Ga feeding ratio of 1:8, AGZS NCs demonstrate a typical blue emission at 470 nm with a narrow full width at half-maximum (fwhm) of 48 nm, which is mainly generated from the band-to-hole recombination rather than the donor-acceptor pair (DAP) recombination. Furthermore, a solution-processed quantum-dot light-emitting device based on AGZS NCs exhibits a narrow electroluminescent bandwidth of 53 nm and high luminance over 123.1 cd m-2, as well as a high external quantum efficiency (EQE) of 0.40%. Our work highlights AGZS NCs with high color purity as an important candidate for blue-light-emitting devices.