Dexter Energy Transfer from Quantum Dots to Closely-Bound Dye Molecules

Quantum dots (QDs) are semiconductor nanocrystals confined in all three dimensions, whose optical properties can be tuned by altering their size.^[1,2] By combining QDs with dye molecules, we can make hybrid QD-dye systems that exhibit efficient energy transfer (ET) from QDs to dyes, important for sensing and lighting applications. ET usually proceeds through Förster resonance energy transfer (FRET), which requires significant spectral overlap between QD emission and dye absorbance, and large oscillator strengths of those transitions. This severely limits the choice of suitable dyes. Perovskite QDs do not require passivating inorganic shells for bright emission. Consequently, we can attach dye molecules directly to their surface, making ET mechanisms beyond FRET accessible. This work explores the design of a CsPbBr₃ QD-dye system with the aim of achieving efficient ET from CsPbBr₃ QDs to dyes with dimethyl iminium binding groups. The close binding of dyes to the CsPbBr₃ surface should facilitate spatial wavefunction overlap. We observe efficient ET from CsPbBr₃ to dyes with minimal spectral overlap. We show by steady-state and time-resolved photoluminescence experiments, that the ET proceeds via the Dexter exchange-type mechanism. This significantly improves the tuneability of such QD-dye systems, opening avenues for QD-molecule hybrids in a wide range of applications, such as lighting.^[3]<br/><br/>References<br/>[1] A. Barfüßer, S. Rieger, A. Dey, A. Tosun, Q. A. Akermann, T. Debnath, J. Feldmann. <i>Nano Lett., 22, 22, 8810–8817 (2022)</i><br/>[2] Q. A. Akkerman, T. P. T. Nguyen, S. C. Boehme, F. Montanarella, D. N. Dirin, P. Wechsler, F. Beiglböck, G. Raino, R. Erni, C. Katan, J. Even, M. V. Kovalenko. <i>Science 377, 1406–1412 (2022)</i><br/>[3] M, Kurashvili, J. Llusar, T. Würthner, D. Ederle, I. Infante, J. Feldmann, Q. A. Akkerman. <i>Manuscript submitted for publication</i>