Clarifying the Controversy over Defect Emission of I‐III‐VI2 Nanocrystals via Pressure Engineering

Abstract

AbstractI–III–VI2 semiconductor nanocrystals (NCs), such as typical AgInS2 NCs, are promising candidates for fluorescent materials because of their lower toxicity and tunable optical properties. However, a long‐standing conventional dispute over the origin of defect emission of AgInS2 NCs restricts the material design and applications. Here, high pressure is introduced to distinguish the photophysical behavior of a core@shell structure of AgInS2@InSx NCs that exhibit both band‐edge (BE) emission and defect emission. Compared with the well‐established dopant mechanism of Ag+:CdS NCs, the decreasing relative shift of defect/BE emissions for AgInS2@InSx NCs excludes the Ag‐related emission associated with radiative free‐to‐bound recombination that contributes to the defect emission of AgInS2 NCs. Identification by the in situ high‐pressure transient spectra and comparative experiments passivated with different ligands, the donor−acceptor pair (DAP) recombination is responsible for the observed defect emission. Likewise, a narrow and strong BE emission with 5.3‐fold enhancement is achieved in AgInS2@InSx NCs by pressure processing. This in turn further confirms the DAP‐related origin of the defect emission. Overall, this study enables high pressure as a tool to resolve the traditional debate under ambient conditions, which facilitates the fundamental photophysical understanding for materials by design applied in solid‐state lighting.