Strong Coupling between Mn<sup>2+</sup> Dopants and CdSe Nanoplatelets Enables Charge-Transfer Transition and Dual Emission
Lifeng Wang, Junhui Wang, Jinglu Sun, You Lv, Tao Ding, Pengfei Cheng, Kaifeng Wu
Abstract
Doping transitional metals into colloidal nanocrystals can significantly modify their excited-state dynamics and enrich their optical and magneto-optical functionalities. Here we synthesize Mn-doped CdSe nanoplatelets and investigate their excited-state dynamics and light-emission mechanisms. Extensive characterizations suggest that Mn 2+ ions are situated near the surface-region of the nanoplatelets. The atomic thinness of nanoplatelets allows for a strong host-dopant coupling, manifested as broadband charge-transfer absorption and emission (near 575 nm) between the host valence band and the dopant d -orbitals. Photoexcitation of the host leads to rapid (a few ps) electron transfer from the conduction band to the d -orbitals, and the resultant charge-transfer state decays within a few ns not only through charge-transfer emission but also generating an excited-state species (likely Mn-Mn dimer) with a characteristic near-infrared emission. These novel photophysics and photochemistry uncovered for quasi-two-dimensional Mn-doped nanocrystals form the basis for optical, magneto-optical, and energy conversion applications using such materials.