Between the Nanosheets: Enhancing Electron–Hole Exchange Interaction for Room-Temperature Magneto-Photoluminescence in Liquid-phase-exfoliated 2D Perovskite

Nanomaterials with a strong room-temperature optical response to magnetic fields are highly desirable for applications in sensing and photonics. Therefore, the ability to tune this response presents an opportunity to develop nanoscale magneto-optical devices. 2D metal halide perovskites are promising materials for optoelectronics, but typically exhibit very weak magneto-optical effects at room temperature. In this article, a 15× enhancement of the magnetic field effect on photoluminescence (magneto-photoluminescence) is demonstrated in colloidal (PEA)₂PbI₄ 2D perovskite nanosheets at room temperature. The results show that an external species can influence the exchange interaction energy and consequently the splitting between bright and dark exciton states in 2D perovskite nanosheets, which ultimately governs the magneto-photoluminescence. Additionally, the average photoluminescence quantum yield (PLQY) is increased from 15.2% in bulk single crystals to 23.1% in nanosheets (with a maximum recorded PLQY of 39.61%) produced using liquid-phase exfoliation, which also exhibited reduced trap emission compared with bulk or tape-exfoliated crystals in this study. This work demonstrates a simple method of engineering exciton states in 2D perovskites, assisting the development of optoelectronic technology and representing a crucial step toward producing nanoscale room-temperature magneto-optical devices.