Dynamic lattice distortions driven by surface trapping in semiconductor nanocrystals

B Guzelturk and BL Cotts and D Jasrasaria and JP Philbin and DA Hanifi and BA Koscher and AD Balan and E Curling and M Zajac and S Park and N Yazdani and C Nyby and V Kamysbayev and S Fischer and Z Nett and XZ Shen and ME Kozina and MF Lin and AH Reid and SP Weathersby and RD Schaller and V Wood and XJ Wang and JA Dionne and DV Talapin and AP Alivisatos and A Salleo and E Rabani and AM Lindenberg, NATURE COMMUNICATIONS, 12, 1860 (2021).

DOI: 10.1038/s41467-021-22116-0

Nonradiative processes limit optoelectronic functionality of nanocrystals and curb their device performance. Nevertheless, the dynamic structural origins of nonradiative relaxations in such materials are not understood. Here, femtosecond electron diffraction measurements corroborated by atomistic simulations uncover transient lattice deformations accompanying radiationless electronic processes in colloidal semiconductor nanocrystals. Investigation of the excitation energy dependence in a core/shell system shows that hot carriers created by a photon energy considerably larger than the bandgap induce structural distortions at nanocrystal surfaces on few picosecond timescales associated with the localization of trapped holes. On the other hand, carriers created by a photon energy close to the bandgap of the core in the same system result in transient lattice heating that occurs on a much longer 200 picosecond timescale, dominated by an Auger heating mechanism. Elucidation of the structural deformations associated with the surface trapping of hot holes provides atomic-scale insights into the mechanisms deteriorating optoelectronic performance and a pathway towards minimizing these losses in nanocrystal devices. Charge trapping can lead to severe nonradiative losses in colloidal semiconductor nanocrystals (NCs). The authors report femtosecond electron diffraction measurements on photoexcited NCs to reveal atomic- scale insights into how localization of charges at trap sites induce surface deformations.

Return to Publications page