Giant Exciton Stokes Shift in Interfacially Prepared Cs(Mn/Pb)Cl3 Alloy Nanoplatelets

Controlling the reabsorption of light by an emittingmaterial isone of the keys to improving the performance of light-emitting devices.We prepare a set of size-dependent Cs(Mn/Pb)Cl-3 alloy nanoplatelets(NPls) with substantial enhancement in the exciton Stokes shift, reducingthe light-reabsorption significantly. We perform interfacial Mn-alloyingusing a shuttling ligand that transports MnCl2 from aqueousto nonaqueous phase and delivers it to NPls. While the exciton Stokesshift in 2-5 monolayer (ML) CsPbBr3 NPls rises from20 to 108 meV, the exciton Stokes shift increases drastically up to600 meV in 2 ML Cs(Mn/Pb)Cl-3 NPls and further reduces uponincreasing the thickness. Moreover, the exciton PL peak in the Mn-alloyNPls remains unperturbed by the quantum-confinement effect. A modelbased on the interplay between Mn2+/Mn3+ duringthe charge transfer process is proposed, accounting for such a largeexciton Stokes shift. Finally, we utilize the large exciton Stokes-shiftedalloy NPls for successful demonstration of white-light generation.