Photoluminescence Quantum Yield and Matrix-Induced Luminescence Enhancement of Colloidal Quantum Dots Embedded in Ionic Crystals

M. Müller, M. Kaiser, G.M. Stachowski, N. Gaponik, U. Resch-Genger, A. Eychmüller

Chem. Mater., 2014, 26 (10), pp 3231–3237
Published April 2014
DOI: 10.1021/cm5009043
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The incorporation of colloidal quantum dots (QDs) into solid matrices, especially ionic salts, holds several advantages for industrial applications. Here, we demonstrated via absolute measurements of photoluminescence quantum yields (PL-QY) that the photoluminescence of aqueous CdTe QDs can be considerably increased upon incorporation into a salt matrix with a simple crystallization procedure. Enhancement factors of up to 2.8 and a PL-QY of 50 to 80%, both in NaCl crystals and incorporated in silicone matrices, were reached. The fact that the achievable PL enhancement factors depend strongly on PL-QY of the parent QDs can be described by the change of the dielectric surrounding and the passivation of the QD surface, modifying radiative and nonradiative rate constants. Time-resolved PL measurements revealed noncorrelating PL lifetimes and PL-QY, suggesting that weakly emissive QDs of the ensemble are more affected by the enhancement mechanism, thereby influencing PL-QY and PL lifetime in a different manner.

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