Ligand-Induced Luminescence Transformation in AgInS2 Nanoparticles: From Defect Emission to Band-Edge Emission

I-III-VI2 semiconductor nanoparticles are strong candidates for fluorescent materials composed of nontoxic elements substituting highly fluorescent CdSe nanoparticles. Photoluminescence of I-III-VI2 nanoparticles essentially arise due to defect emission characterized by a broad spectral feature. Band-edge emission exhibits radiation with high monochromaticity, which can drastically expand its application range. Hence, numerous studies were conducted to realize band-edge emission. A successful observation of the band-edge emission was reported only when fabricating GaSx or InSx shells around AgInS2 nanoparticles via surface trap site passivation. This study demonstrates a much easier method of providing band-edge emission from AgInS2 nanoparticles using organic ligands of trioctylphosphine (TOP). Along with the TOP ligand formation around AgInS2 nanoparticles, the defect emission increases once and then decreases in conjunction with the appearance of the band-edge emission. Therefore, TOP ligands can passivate carrier trapping sites for radiative recombination as well as fluorescence quenching sites.