Exciton fate in semiconductor nanocrystals at elevated temperatures

Hole trapping outcompetes exciton deactivation

Clare E. Rowland, Richard D Schaller

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

The tens-of-percent photoluminescence (PL) quantum yields routinely obtained for colloidally prepared CdSe semiconductor nanocrystals (NCs) decrease substantially with temperature elevation. While such PL efficiency loss has direct consequences for applications ranging from light-emitting diodes and lasers to photovoltaics under solar concentration, the origin of this loss is currently not established, hindering synthetic efforts to design materials with robust performance. Here, for the first time, we utilize transient absorption and ultrafast PL in addition to static PL and time-correlated single photon counting, to characterize CdSe core-only and CdSe/ZnS core/shell NCs up to temperatures as high as 800 K. For multiple particle sizes, loss of PL efficiency as a function of temperature elevation is more severe and less reversible for core-only NCs than for core/shell NCs. Ultrafast measurements performed at elevated sample temperatures indicate that thermally activated trapping of individual carriers dominates the nonradiative loss of excitons. Through a combination of spectroscopic techniques, we identify the primary carrier loss process as hole trapping in particular. These findings support the notion that extrinsic trapping effects out-compete intrinsic exciton deactivation at high temperature and point to realizable improvements in thermally robust optoelectronic performance.

Original languageEnglish
Pages (from-to)17337-17343
Number of pages7
JournalJournal of Physical Chemistry C
Volume117
Issue number33
DOIs
Publication statusPublished - Aug 22 2013

Fingerprint

Excitons
deactivation
Nanocrystals
Photoluminescence
nanocrystals
trapping
excitons
Semiconductor materials
photoluminescence
Temperature
temperature
Quantum yield
Optoelectronic devices
Light emitting diodes
counting
light emitting diodes
Photons
Particle size
LDS 751
Lasers

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Exciton fate in semiconductor nanocrystals at elevated temperatures : Hole trapping outcompetes exciton deactivation. / Rowland, Clare E.; Schaller, Richard D.

In: Journal of Physical Chemistry C, Vol. 117, No. 33, 22.08.2013, p. 17337-17343.

Research output: Contribution to journalArticle

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