Efficient Quantum-Dot Light-Emitting Diodes Based on Solvent-Annealed SnO₂ Electron-Transport Layers

Abstract

Due to the sensitivity of ZnO nanoparticles to water and oxygen, the hybrid quantum-dot light-emitting devices (QLEDs) based on ZnO electron-transport layers (ETLs) suffer from shelf stability and uncontrollable positive aging problems. Tin oxide (SnO 2 ) is considered as an ideal alternative to ZnO as the ETL in QLEDs to improve their shelf stability. Currently, the SnO 2 -based device still suffers from poor efficiency. Herein solvent vapor annealing (SVA) is employed to reduce the roughness of SnO 2 nanoparticle films, which suppresses the leakage current and enhances the device performance. Compared with the device with pristine SnO 2 , the maximum brightness and current efficiency (10.8 cd/A) of QLEDs based on solvent vapor annealed SnO 2 are enhanced by 25.3% and 36.6%, respectively, being comparable to the ZnO device (11.0 cd/A). Moreover, SVA processing also has a positive effect on the device shelf stability, which is attributed to the dense interface between SnO 2 and quantum dots due to the reduced surface roughness of SnO 2 films.

Zn-Doped SnO2 NPs as Electron Transport Layer in Green CdSe/ZnS Quantum Dot Light-Emitting Diodes

“…In 2020, Liu et al effectively controlled the particle size of SnO 2 NPs by nonaqueous synthesis, and the QLED with ethanolamine-modified SnO 2 ETL reached a higher operating life of 5.1 h . Ji et al obtained a smooth SnO 2 film by solvent vapor annealing postprocessing, and the unencapsulated devices remained stable after being stored in air for 108 h . Chen et al mixed and stirred the solvothermal-prepared SnO 2 NPs with tetramethylammonium hydroxide (TMAH) to obtain a clear and transparent solution .…”

“…The stable dispersion of SnO 2 NPs in the solvent facilitates the uniformity of the SnO 2 film, which ensures the stability of the device. In 2020, Liu et al effectively controlled the particle size of SnO 2 NPs by nonaqueous synthesis, and the QLED with ethanolaminemodified SnO 2 ETL reached a higher operating life of 5.1 h. 29 Ji et al obtained a smooth SnO 2 film by solvent vapor annealing postprocessing, and the unencapsulated devices remained stable after being stored in air for 108 h. 13 Chen et al mixed and stirred the solvothermal-prepared SnO 2 NPs with tetramethylammonium hydroxide (TMAH) to obtain a clear and transparent solution. 30 The formation of hydrocarbon group ligands on the surface is attributed to the durable and stable presence of SnO 2 NPs in ethanol.…”

“…A typical QLED usually has a sandwich structure, which is mainly composed of an electron transport layer (ETL), a QD emitting layer (EML), a hole transport layer (HTL), and a hole-injection layer (HIL). The electron transport layer is mainly categorized into the organic electron transport materials (e.g., 2,2′,2″-(l,3,5-benzenetriyl)-tris­( l -phenyl-l-H-benzimidazole) (TPBi) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)) and inorganic metal oxide nanoparticles (NPs) (e.g., SnO 2 NPs, , ZnO NPs, − and TiO 2 NPs − ). The QLEDs based on metal oxide NPs show an excellent electroluminescence (EL) performance.…”

Sn-doped ZnO for efficient and stable quantum dot light-emitting diodes via a microchannel synthesis strategy

“…[25][26][27] SnO 2 -based ETLs have comparable photoelectric characteristics to ZnO, as well as a more inert surface chemistry which is advantageous for enhancing the operational stability of photoelectric devices. [28][29][30][31] However, SnO 2 NCs have poor dispersion in alcoholic solvents, rendering them incompatible with the conventional fabrication process of QLED structures.…”

Memory-Enabled Quantum-Dot Light-Emitting Diodes

“…The QLEDs with an inverted device structure, as shown in Figure a, are fabricated. The schematic diagram shown in Figure S1 exhibits the energy level structure of each functional layer and the carrier dynamics processes. − The synthesis of ZnO NPs and the fabrication procedures of the devices are described in detail in our previous reports. − A WO x film fabricated under humidity of 24% is inserted between ITO and ZnO as the HSL, with the thicknesses of ∼3, 7, 12, and 17 nm. The WO x films were fabricated by spin-coating the precursor solution (5, 10, 15, and 20 mg/mL) at 3000 rpm for 60 s in atmosphere, followed by thermal annealing at 150 °C.…”