Bright InP quantum dots by Ga-doping for red emitters
Environment-friendly indium phosphide (InP)-based quantum dots (QDs) with efficient red-emitting properties are sufficiently needed to satisfy the requirement of burgeoning display and lighting technology. Currently, the syntheses of InP QDs using tris(trimethylsilyl)phosphine as the precursor are highly toxic and expensive. Herein, we successfully introduced gallium (Ga) ions into tris(dimethylamino)phosphine-based red InP cores through thermally-promoted cation exchange, and the obtained Ga-doped InP cores exhibited significantly increased photoluminescence quantum yields (PLQY) of up to 26%. The existence of Ga was directly confirmed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, and the functions of Ga were systematically studied. After subsequent coating of Ga-doped InP cores with ZnSeS and ZnS shells, the resulting Ga-InP/ZnSeS/ZnS QDs achieved a high PLQY of 62% with an emission maximum at 640 nm. In contrast, without Ga-doping, the PLQY only attained 36% using the same synthetic approach. This indicated an approximate 1.7-fold increase in PLQY. The enhancement of photoluminescence was related to the Ga 3+ , as it not only passivated surface defects of InP cores but also reduced core-shell interface stress. The Ga-InP/ZnSeS/ZnS QDs exhibited good stability towards heat treatment and ultraviolet (UV) irradiation. Moreover, the red light-emitting diode (LED) based on Ga-InP/ZnSeS/ZnS QDs performed well in a wide injected current range of 2 to 200 mA, with a maximum power efficiency of 0.68 lm/W. This work showcases Ga-doping through cation exchange as a promising strategy for enhancing the efficiency of InP-based red emitters.
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