Manipulating the Intersystem Crossing Process in Atomically Precise Gold Nanoclusters

Atomically precise metal nanoclusters (NCs) have attracted wide research interest. In terms of electronic properties, a striking feature of such NCs is triplet excited state generation with remarkably high efficiency. Experimental and theoretical findings indicate that NCs are promising luminescent materials with room-temperature phosphorescence and thermally activated delayed fluorescence. However, the manipulation of triplet formation remains difficult due to the complexity of the electron dynamics in NCs. In this Perspective, we summarize recent advances in fundamental research on this topic. We first illustrate the typical spectral features of the triplet state and analytical methods such as time-resolved photoluminescence (TR-PL), transient absorption (TA), and temperature-dependent PL spectroscopies. We then focus on the recent understating of triplet states in NCs and how to manipulate the triplet states. Finally, we present the remaining challenges and future outlooks. This Perspective aims to contribute to the further design of NCs for efficient ISC processes and applications of the triplet states. With a fundamental understanding of the triplet states in NCs, one may develop star materials for triplet utilization in optoelectronics, photocatalysis, and near-infrared solar energy upconversion.