Determination of absolute quantum yields of luminescing nanomaterials over a broad spectral range: from the integrating sphere theory to the correct methodology

Abstract

Determination of fluorescence or photo- and electro-luminescence quantum yield (QY) is of increasing importance for standardization of novel light-emitting materials like semiconductor quantum dots. The most straightforward spectroscopic QY measurement technique is based on the exploitation of an integrating sphere (IS). We propose a compact set-up and procedure for reliable measurements of QY over a broad excitation spectral range which uses excitation by light-emitting diodes. Starting from the general IS theory we show that (i) a variable excitation pattern has no fatal influence on the QY determination and (ii) a simple two-configuration experiment is an adequate basis of the correct experimental procedure. Then we give guidelines for the QY experiment and calculations as well as a few practical examples and error analysis. Our comprehensive description of absolute luminescence QY techniques based on the IS theory has a general applicability not restricted to the apparatus described in this paper.