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Inverted Hybrid Light-Emitting Diodes Using Carbon Dots as Selective Contacts: The Effect of Surface Ligands
摘要： We describe the use of carbon dots (C-Dots) as selective contacts for electronic holes in inverted hybrid light-emitting diodes. Moreover, we have studied the effect of the C-Dots’ amine-derivative surface ligands and their impact on the device performance. The different surface ligands affect not only the optical properties of the C-Dots but also the device turn-on voltage and the luminance parameters despite not forming part of the emissive layer. For instance, the C-Dots capped with the aromatic ring p-phenylenediamine show unfavorable effects, whereas the effect of nonaromatic capping ligands depends upon the length of their molecular backbone.
关键词： capping ligands,amine-based ligands,light-emitting diodes,carbon dots,optoelectronic properties
更新于2025-09-23 15:21:01
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Enhancing Charge Carrier Delocalization in Perovskite Quantum Dot Solids with Energetically Aligned Conjugated Capping Ligands
摘要： Compared to bulk perovskites, charge transport in perovskite quantum dot (PQD) solids is limited. To address this issue, energetically aligned capping ligands were used to prepare methylammonium lead bromide (MAPbBr3) PQDs towards enhancing surface charge carrier density in PQD solids. Trans-cinnamic acid (TCA) and its derivates, functionalized with electron-donating or electron-withdrawing groups to modulate energy levels, are used as passivating exciton-delocalizing ligands (EDLs) to decrease the energy gap with respect to the PQD core. 3,3-diphenylpropylamine (DPPA) ligand is shown to stabilize EDLs on the PQD surface through π-π stacking intermolecular interaction, mitigating charge trapping and non-radiative decay. Passivation using EDLs in combination with DPPA increases the photoluminescence (PL) quantum yield (QY) (90%), photoconductivity, extraction, mobility, transport time, and lifetime of charge carriers in PQD solids. Prototype PQD-based light-emitting diodes (LEDs) were demonstrated with a low turn-on voltage of 2.5 V.
关键词： charge transport,light-emitting diodes,capping ligands,perovskite quantum dots,photoluminescence
更新于2025-09-19 17:13:59
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Room temperature synthesis of cesium lead bromide perovskite magic sized clusters with controlled ratio of carboxylic acid and benzylamine capping ligands
摘要： We demonstrate the synthesis of cesium lead bromide (CsPbBr3) perovskite magic sized clusters (PMSCs) and how to control the transformation from CsPbBr3 perovskite quantum dots (PQDs) to PMSCs by varying the amount of organic carboxylic acids (CAs), including mesitylacetic acid (MAA), oleic acid (OA), and phenylacetic acid (PAA), along with benzylamine (BZA) as capping ligands at room temperature. The PQDs and PMSCs are characterized by means of XRD, UV/vis, photoluminescence (PL), time-resolved PL (TRPL), and X-ray-photoelectron spectroscopy (XPS). The concentration of CAs affects the excitonic absorption of both the CsPbBr3 PMSCs (λ ? 389–428 nm) and CsPbBr3 PQDs (λ ? 460–516 nm), with high concentration of CAs favoring CsPbBr3 PMSCs over PQDs. With PAA at 45.45 mM, pure CsPbBr3 PMSCs can be generated, which does not happen for MAA or OA, suggesting that PAA is a stronger ligand than MAA and OA. The results suggest that PMSCs require better passivation or stronger ligands than PQDs. This study establishes a simple and general method for synthesizing CsPbBr3 PMSCs using a combination of BZA and CA capping ligands as a highly effective dual passivation system.
关键词： Controlled ratio of capping ligands,Room temperature,Perovskite quantum dots (PQDs),Perovskite magic sized clusters (PMSCs),Cesium lead bromide perovskite
更新于2025-09-16 10:30:52
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PbS Quantum Dots as Additives in Methylammonium Halide Perovskite Solar Cells: the Effect of Quantum Dot Capping
摘要： Colloidal PbS quantum dots (QDs) have been successfully employed as additives in Halide Perovskite Solar Cells (PSCs) acting as nucleation centers in the perovskite crystallization process. For this strategy, the surface functionalization of the QD, controlled via the use of different capping ligands, is likely of key importance. In this work, we examine the influence of the PbS QD capping on the photovoltaic performance of methylammonium lead iodide PSCs. We test PSCs fabricated with PbS QD additives with different capping ligands including methylammonium lead iodide (MAPI), cesium lead iodide (CsPI) and 4-aminobenzoic acid (ABA). Both the presence of PbS QDs and the specific capping used have a significant effect on the properties of the deposited perovskite layer, which affects, in turn, the photovoltaic performance. For all capping ligands used, the inclusion of PbS QDs leads to the formation of perovskite films with larger grain size, improving, in addition, the crystalline preferential orientation and the crystallinity. Yet, differences between capping agents were observed. The use of QDs with ABA capping had higher impact on the morphological properties while the employment of CsPI ligand was more effective on the optical properties of the perovskite films. Taking advantage of the improved properties, PSCs based on the perovskite films with embedded PbS QDs exhibit an enhanced photovoltaic performance, observing the highest increase with ABA capping. Moreover, bulk recombination via trap states is reduced when the ABA ligand is used as capping of the PbS QD additives in the perovskite film. We demonstrate how surface chemistry engineering of PbS QD additives in solution-processed perovskite films opens a new approach towards the design of high quality materials, paving the way to improved optoelectronic properties and more efficient photovoltaic devices.
关键词： nucleation centers,PbS quantum dots,perovskite solar cells,photovoltaic performance,capping ligands
更新于2025-09-11 14:15:04