The aggregate luminescence behavior of organic luminescent materials has been studied extensively. As a new kind of luminescent nanomaterials, carbonized polymer dots (CPDs) not only inherit the stability and biocompatibility of carbon materials, but also possess the luminescence tunability, water solubility, and high photoluminescence quantum yield of organic luminescent materials, rendering them a strong candidate for the next generation of light-emitting materials. Previously, people mainly understood its luminescence from the perspective of carbon materials, but some luminescence mechanisms are still unclear. In this review, we discuss the luminescence mechanism by referring to organic luminescent materials with emphasis on their aggregation behavior. Firstly, three representative aggregate luminescence phenomena of organic luminescent materials are briefly introduced. Chromophores present in CPDs are elaborated to further discuss the potential interactions between them, with emphasis on the role of crosslinked polymer networks. On this basis, some special luminescence phenomena of CPDs in the aggregate state are summarized, and relevant mechanisms are discussed in detail to consolidate relevant statements.
Revealing the photoluminescence (PL) origin and mechanism is a most vital but challenging topic of carbon dots. Herein, confined-domain crosslink-enhanced emission (CEE) effect was first studied by a well-designed model system of carbonized polymer dots (CPDs), serving as an important supplement to CEE in the aspect of spatial interactions. The “addition-condensation polymerization” strategy was adopted to construct CPDs with substituents exerting different degrees of steric hindrance. The effect of confined-domain CEE on the structure and luminescence properties of CPDs have been systematically investigated by combining characterizations and theoretical calculations. Such tunable spatial interactions dominated the coupling strength of the luminophores in one particle, and eventually resulted in the modulated PL properties of CPDs. These findings provide insights into the structural advantages and the PL mechanism of CPDs, which are of general significance to the further development of CPDs with tailored properties.
Film uniformity of solution-processed layers is the cornerstone of large-area perovskite light-emitting diodes, which is often determined by the ‘coffee-ring effect’. Here we demonstrate a second factor that cannot be ignored is the solid-liquid interface interaction between substrate and precursor and can be optimized to eliminate rings. A perovskite film with rings can be formed when cations dominate the solid-liquid interface interaction; whereas smooth and homogeneous perovskite emitting layers are generated when anions and anion groups dominate the interaction. This is due to the fact that the type of ions anchored to the substrate can determine how the subsequent film grows. This interfacial interaction is adjusted using carbonized polymer dots, who also orient the perovskite crystals and passivate their buried traps, enabling a 225 mm2 large-area perovskite light-emitting diode with a high efficiency of 20.2%.
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