Surface Metal Salt Modulating and Inner-Shell Doping of Green Indium Phosphide Quantum Dots toward High Efficiency and Narrow Emission

Low-toxicity indium phosphide (InP) QDs are considered to be an ideal alternative to heavy metal QDs and have emerged as a promising candidate for next-generation optoelectronic applications. However, the optical performance of InP QDs still lags behind that of Cd-based QDs, partly due to the surface traps caused by the lattice mismatch between InP and ZnS. Here, Al, Ga, and In salts are used to modify the surface of the green InP core before the growth of the inner shell of ZnSeS. These metal ions are thought to play an effective role in removing P dangling bonds on the surface of the InP core. By using AlCl3 as a modifier, the line width is reduced from 36.7 to 35.6 nm. Then, a small amount of Mn ions is doped in the second step of ZnSeS inner-shell growth to form the inner-shell structure of Zn(Mn)SeS alloys. Mn doping may change the crystal structure of ZnSeS, and reduce interfacial defects and stresses. After surface metal salt modulating and inner-shell doping, Al-, Ga-, and In-InP QDs all reach better efficiency and line width than the untreated ones. And the best performance is obtained by Ga-InP/Zn(Mn)SeS/ZnS QDs with a fwhm of 35 nm and a PLQY of 94%.