Perovskite quantum dots were purchased from PlasmaChem GmbH. The FS5 can be configured to measure the absorption spectra, emission spectra, lifetime and quantum yield of materials such as perovskite quantum dots. Further research is required to improve the properties of perovskite quantum dots and the primary techniques to characterise these materials are photoluminescence and absorption spectroscopy.įigure 2: The FS5 Spectrofluorometer with TCSPC electronics and pulsed diode laser. The solution processability, band gap tuneability and high PLQY that has led to the success of perovskite solar cells also make them promising candidates as a new class of quantum dots. Halide perovskites have already received widespread attention in the scientific community for their role as low cost, high efficiency absorbers in photovoltaic cells. Recently, quantum dots based on halide perovskite semiconductors have been attracting increasing attention. Quantum dots have been traditionally dominated by the chalcogenides such as cadmium telluride and zinc selenide. Nanoparticles that are small enough to have their band gap influenced by quantum confinement are known as quantum dots and by precisely controlling the size of the quantum dots during synthesis the photoluminescence emission and absorption wavelengths can be finely tuned, which is ideal for optoelectronic applications.įigure 1: The influence of particle size on the band gap and photoluminescence emission wavelength of quantum dots due to quantum confinement. There are fewer atomic orbitals overlapping and the valence and conduction bands are no longer continuous and are instead formed of discrete energy levels, and more importantly the band gap between the valence and conduction bands becomes wider which is known as quantum confinement (Figure 1). However, if the semiconductor is reduced to a nanoscale size the situation changes. In a bulk semiconductor the number of atoms is very large and the overlap of this high number of atomic orbitals creates a continuum of closely spaced ‘molecular’ orbitals which form the valence and conduction bands. The key attraction of quantum dots is the superb control available over their band gap due to quantum confinement. In addition, their light emission properties also make them a promising new class of fluorescent probe for biomedical fluorescence imaging to replace traditional organic small molecule probes. These properties make quantum dots ideal for optoelectronic devices such as light emitting diodes and semiconductor lasers where they serve as emitters or in photodiodes and solar cells where they serve equally well as light absorbers. Semiconductor quantum dots possess an array of attractive properties, including high photoluminescence quantum yields (PLQY), solution processability and highly tuneable band gaps. In this application note a complete photophysical characterisation, comprising of absorption spectra, photoluminescence spectra, photoluminescence lifetime, and quantum yield of two perovskite quantum dots is carried out using the versatile FS5 Spectrofluorometer. Perovskite Quantum Dots are a promising new class of light emitters.
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