Nature Communications 2015-01-01

Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals.

Sotirios Christodoulou, Fernando Rajadell, Alberto Casu, Gianfranco Vaccaro, Joel Q Grim, Alessandro Genovese, Liberato Manna, Juan I Climente, Francesco Meinardi, Gabriele Rainò, Thilo Stöferle, Rainer F Mahrt, Josep Planelles, Sergio Brovelli, Iwan Moreels

Index: Nat. Commun. 6 , 7905, (2015)

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Abstract

Strain in colloidal heteronanocrystals with non-centrosymmetric lattices presents a unique opportunity for controlling optoelectronic properties and adds a new degree of freedom to existing wavefunction engineering and doping paradigms. We synthesized wurtzite CdSe nanorods embedded in a thick CdS shell, hereby exploiting the large lattice mismatch between the two domains to generate a compressive strain of the CdSe core and a strong piezoelectric potential along its c-axis. Efficient charge separation results in an indirect ground-state transition with a lifetime of several microseconds, almost one order of magnitude longer than any other CdSe/CdS nanocrystal. Higher excited states recombine radiatively in the nanosecond time range, due to increasingly overlapping excited-state orbitals. k˙p calculations confirm the importance of the anisotropic shape and crystal structure in the buildup of the piezoelectric potential. Strain engineering thus presents an efficient approach to highly tunable single- and multiexciton interactions, driven by a dedicated core/shell nanocrystal design.