Surface depletion effects in bromide-ligated colloidal cadmium selenide nanoplatelets: toward efficient emission at high temperature

• Main Authors: Zhang, Zitong, Thung, Yi Tian, Wang, Lin, Chen, Xiaoxuan, Ding, Lu, Fan, Weijun, Sun, Handong
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2022
• Subjects: Engineering::Materials::Photonics and optoelectronics materials; Colloidal Nanostrucrures; Depletion Region; Surface Traps; Halide Treatment; Thermal Quenching
• Online Access: https://hdl.handle.net/10356/156909
• Institution: Nanyang Technological University

The colloidal semiconductor nanoplatelet (NPL) with broad ligand-semiconductor interface is an ideal system for surface science investigation, but the study regarding depletion effects in NPLs remains lacking. Herein we explore such effects in colloidal CdSe NPLs through Br ligation. Apart from improved brightness and red-shifted optical features, we also experimentally observed abnormal negative thermal quenching phenomena in bromideligated CdSe NPLs over 200 K under a cryogenic environment and up to 383 K under an ambient environment, which was absent in pristine NPLs. We speculate that the surface depletion effect shall account for these anomalous phenomena due to the susceptibility of the surface depletion region on photoexcited carrier concentration and surface condition. The existence of the depletion layer in NPLs is also validated quantitatively with k·p simulation. Besides offering an alternative explanation on the red-shifted optical properties of CdSe NPLs by Br-ligation, our findings pave the new route toward solution-processed NPLs-based optoelectronics with boosted thermal resistance.