Turning Weakly Luminescent SnO₂ Nanocrystals into Tunable and Efficient Light Emitters by Aliovalent Alloying

We report the synthesis of ternary gallium tin oxide nanocrystals, and demonstrate that their photoluminescence can be tuned through the visible region by changing Ga:Sn ratio. By substitutional doping with Ga³⁺, the PL intensity of SnO₂ nanocrystals is enhanced by nearly 3 orders of magnitude, reaching photoluminescence quantum yield of >40%. Increase in PL intensity is attributed to the formation of donor and acceptor pairs, and the increase in emission energy is discussed in the context of band-gap expansion and stronger Coulomb interaction between charged defect sites. Time-resolved and steady-state photoluminescence spectroscopies reveal that the interaction of extrinsic and native defects is driven by the nature of the dopant ion. By adjusting various reaction conditions, we prepared the nanocrystals with nearly ideal scotopic-to-photopic ratio and a quantum yield of ca. 34%, attesting to the potential of these nanocrystals for general lighting applications. The results of this work provide new insight into the role of defect chemistry in tailoring the optoelectronic properties of transparent metal oxide nanocrystals, and pave the way for the rational design of light sources and photonic devices with high photoluminescence efficiency, minimum toxicity, and optimal lighting characteristics