Abstract
In this paper, high quality green-emitting CsPbBr3 quantum dots (QDs) are successfully synthesized by hot-injection method. Different injection temperatures are tested to optimize the synthesis conditions. High brightness with the photoluminescence (PL) quantum yields (QYs) up to 90% and narrow size-distribution with the full width at half-maximum (FWHM) of 18.5 nm are obtained under the optimized conditions. Green light emitting diodes (LEDs) based on the CsPbBr3 QDs are successfully demonstrated by combining solution method with vapor deposition method. Composite films of poly[9,9-dioctylfluorene-co- N-[4-(3-methylpropyl)]-diphenylamine] (TFB) and bathocuproine (BCP) layers are chosen as the hole-transporting and the electron-transporting layers, respectively. The highly bright green QD-based light-emitting devices (QLEDs) showing maximum luminance up to 46,000 cd/m2 with a low turn on voltage of 2.3 V, and peak external quantum efficiency (EQE) of 5.7%, corresponding to 19.9 cd/A in luminance efficiency. These devices also show high color purity for electroluminescence (EL) with FWHM <20 nm, and no redshift and broadening with increasing voltage as well as a spectral match between PL and EL.
Highlights
Quantum dots based light-emitting devices (QLEDs) are very attractive to industry and academia for potential applications in high color rendering index (CRI) solid-state lighting and high color saturation displays due to their tunable emission range, narrow emission linewidth, and high photoluminescence (PL) efficiencies throughout the visible light region (Shirasaki et al, 2013; Tan et al, 2014)
Inorganic perovskite quantum dots (QDs) have the advantages of conventional inorganic QDs, such as high photoluminescence quantum yields (QYs), wide wavelength tunability, very high color purity [full width at half maximum (FWHM) < 20 nm], and show low material cost, tunable band gap, with a reasonable ionization energy (IE), and easy to scale up synthesis which are incomparable over traditional QDs (Tan et al, 2014; Protesescu et al, 2015; Song et al, 2015; Wang et al, 2015; Colella et al, 2016)
It is found that the growth temperature plays a crucial role rather than the growth time on the QDs morphology and size, as the nucleation and growth kinetics are very fast, the majority of growth occurs within the first several seconds
Summary
Quantum dots based light-emitting devices (QLEDs) are very attractive to industry and academia for potential applications in high color rendering index (CRI) solid-state lighting and high color saturation displays due to their tunable emission range, narrow emission linewidth, and high photoluminescence (PL) efficiencies throughout the visible light region (Shirasaki et al, 2013; Tan et al, 2014). Facile thermal ionization of excitons with low binding energy generated in the perovskite layer results substantial luminescence quenching in CsPbBr3 based QLEDs. Secondly, low film quality of CsPbBr3 QDs. When using the traditional spin-coating method for the preparation of inorganic perovskite film, in the process of heating to remove the solvent and surfactant, many pinholes, cuboids of large grain size, and crack are created, such film is easy to cause leakage current and unable to meet the requirements of high performance devices. A uniform and continuous morphology of perovskite film affecting the subsequent deposition of functional layers with solution procedures (Bade et al, 2015, 2017; Li G. et al, 2015; Li J. et al, 2015)
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