Carrier multiplication yields in PbS and PbSe nanocrystals measured by transient photoluminescence

By Gautham P Nair, S. Geyer, Liang Chang, Moungi G. Bawendi. 2008

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We report here an assessment of carrier multiplication (CM) yields in PbSe and PbS nanocrystals (NCs) by a quantitative analysis of biexciton and exciton dynamics in transient photoluminescence decays. Interest in CM, the generation of more than one electron and hole in a semiconductor after absorption of one photon, has renewed in recent years because of reports suggesting greatly increased efficiencies in nanocrystalline materials compared to the bulk form, in which CM was otherwise too weak to be of consequence in photovoltaic energy conversion devices. In our PbSe and PbS NC samples, however, we estimate using transient photoluminescence that at most 0.25 additional e-h pairs are generated per photon even at energies hv > 5Eg, instead of the much higher values reported in the literature. We argue by comparing NC CM estimates and reported bulk values on an absolute energy basis, which we justify as appropriate on physical grounds, that the data reported thus far are inconclusive with respect to the importance of nanoscale-specific phenomena in the CM process.

Subfields: Electrical and Electronic Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/ad260812e8b42db3ba0f7737bb60e9fb5e468b2c

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Citations in the corpus

Nanostructured materials for photon detection. (2010, background): “Furthermore, the energetic threshold and yield of MEG have been the subject of debate, with variations arising as a function of spectroscopic technique and sample preparatio”
Solar cells from colloidal nanocrystals: Fundamentals, materials, devices, and economics (2009, result): “[84] but did observe enhanced QYs in PbSe and PbS NCs [85] with lower efficiencies than previous reports [11,12,86].”