Temperature dependent optical properties of PbS nanocrystals.
A comprehensive study of the optical properties of PbS nanocrystals (NCs) is reported that includes the temperature dependent absorption, photoluminescence (PL) and PL lifetime in the range of 3-300 K. The absorption and PL are found to display different temperature dependent behaviour though both redshift as temperature is reduced. This results in a temperature dependent Stokes shift which increases from ∼75 meV at 300 K with reducing temperature until saturating at ∼130 meV below ∼150 K prior to a small reduction to 125 meV upon cooling from 25 to 3 K. The PL lifetime is found to be single exponential at 3 K with a lifetime of τ(1) = 6.5 μs. Above 3 K biexponential behaviour is observed with the lifetime for each process displaying a different temperature dependence. The Stokes shift is modelled using a three-level rate equation model incorporating temperature dependent parameter values obtained via fitting phenomenological relationships to the observed absorption and PL behaviour. This results in a predicted energy difference between the two emitting states of ∼6 meV which is close to the excitonic exchange energy splitting predicted theoretically for these systems.
Advanced Technology Institute, University of Surrey, Guildford, Surrey GU2 7XH, UK.
M N
MN
Nordin
Juerong
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Li
S K
SK
Clowes
R J
RJ
Curry
D003460:Crystallization / Q000379:methods*; D007854:Lead / Q000737:chemistry*; D049449:Luminescence; D008163:Luminescent Measurements / Q000379:methods*; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012031:Refractometry / Q000379:methods*; D018036:Selenium Compounds / Q000737:chemistry*; D013696:Temperature
D018036:Selenium Compounds; C088065:lead selenide; D007854:Lead