Band-edge oscillator strength of colloidal CdSe/CdS dot-in-rods: comparison of absorption and time-resolved fluorescence spectroscopy.
We studied the oscillator strength fgapof the band gap transition in heteronanocrystals (hNCs) with a spherical CdSe core embedded in an elongated CdS shell. A comparison with fgapof core-only CdSe NCs confirmed a reduction of the electron-hole overlap in hNCs with a band gap larger than 2.05 eV or smaller than 1.98 eV. However, the decrease in fgapis limited to about 50% when compared to CdSe NCs, suggesting that residual confinement still localizes the electron near the core. We correlated fgapwith the radiative lifetime obtained from multiexponential photoluminescence (PL) decay traces. The different components were attributed to radiative decay, or deep and shallow carrier trapping, respectively, using the PL quantum efficiency (QE) as a guideline. Our data highlight the challenges associated when extracting the radiative decay, and demonstrate the added value of absorption spectroscopy to obtain the band-edge oscillator strength and the associated radiative recombination rate in colloidal hNCs.
Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. iwan.moreels@iit.it remo.proietti@iit.it and Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Angeloni
Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. iwan.moreels@iit.it remo.proietti@iit.it and Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Raja
Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. iwan.moreels@iit.it remo.proietti@iit.it and Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
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Polovitsyn
Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. iwan.moreels@iit.it remo.proietti@iit.it.
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De Donato
Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. iwan.moreels@iit.it remo.proietti@iit.it.
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Zaccaria
Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy. iwan.moreels@iit.it remo.proietti@iit.it.
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http://orcid.org/0000-0003-3998-7618
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Moreels