Linear Absorption and Photoluminescence of CdSe and CdSe-CdTe Nanoplatelets

Ulrike Woggon^a, Riccardo Scott^a, Alexander Achtstein^a^,^b, Laurens Siebbeles^b, Anatol Prudnikau^c, Artsiom Antanovich^c, Mikhail Artemyev^c

^aDelft University of Technology, The Netherlands, Julianalaan, 136, Delft, Netherlands

^bInstitute for Physico Chemical Problems, BSU Minsk, Leningradskaya 14, 220030 Minsk, Belarus

Materials for Sustainable Development Conference (MATSUS)
Proceedings of September Meeting 2016 (NFM16)

Berlin, Germany, 2016 September 5th - 13th

Organizers: Marin Alexe, Enrique Cánovas, Celso de Mello Donega, Ivan Infante, Thomas Kirchartz, Maksym Kovalenko, Federico Rosei, Lukas Schmidt-Mende, Laurens Siebbeles, Peter Strasser, Teodor K Todorov, Roel van de Krol and Ulrike Woggon

Oral, Alexander Achtstein, presentation 310
Publication date: 14th June 2016

We investigate the optical absorption properties of colloidal CdSe nanoplatelets.¹ We compare ICP-AES measurements on their intrinsic absorption coefficients µi with a theoretical approach. The platelets' intrinsic absorption coefficients µ_i are strongly thickness and aspect ratio dependent, enabling to tune the absorption properties of this material class by the lateral size and thickness and to obtain more efficient absorbers. The obtained µ_i values can be used for concentration determination of CdSe nanoplatelets in solution² and solid films. We investigate type II CdSe–CdTe core–lateral shell nanoplatelets. From a kinetic analysis of the photoluminescence decay and the temperature dependent quantum yield we deduce the temperature dependence of the non-radiative and radiative lifetimes. In line with theoretical predictions we observe a strong increase of the radiative lifetime with temperature. Comparing core only and hetero platelets a significant prolongation of the radiative lifetime in type II platelets by two orders in magnitude is observed, while the quantum yield is barely affected. In a careful analysis of the PL decay transients we compare different recombination models, including electron hole pairs and exciton decay, being relevant for the applicability of those structures in photonic applications like solar cells or lasers. We conclude that the observed biexponential PL decay behavior in hetero platelets is predominately due to spatially indirect excitons.³

References:

1) Achtstein et al., J. Phys. Chem. C 119, 20156 (2015)

2) Scott and Achtstein et al., Nano Lett. 15, 4985 (2015)

3) Scott and Achtstein et al., PCCP 18, 3197 (2016)

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