https://scholar.dgist.ac.kr/handle/20.500.11750/243 2026-04-04T14:20:19Z https://scholar.dgist.ac.kr/handle/20.500.11750/59986 Title: Thick ZnS Shells on CsPbBr3Quantum Dots by Colloidal-Atomic Layer Deposition for Enhanced Photoluminescence and Stability Author(s): Teku, Justice Agbeshie; Taylor, Derrick Allan; Lee, Jong-Soo Abstract: The colloidal-atomic layer deposition (c-ALD) method is employed to grow a zinc sulfide (ZnS) shell on CsPbBr3 perovskite quantum dots (PeQDs) to form CsPbBr3/ZnS core/shell heterostructures to address the intrinsic stability challenges of PeQDs. The c-ALD process offers layer by layer control over the thickness of the shell, enabling uniform and conformal encapsulation, which significantly passivates the surface defects and enhances the optical properties of the PeQDs. This approach significantly improves photoluminescence quantum yield, increases environmental stability, and prolongs the average radiative lifetime of the CsPbBr3 PeQDs. The structural and spectroscopic analysis confirms the formation of a thick and uniform ZnS shell. Furthermore, the resulting core/shell PeQDs exhibit exceptional thermal, photostability, and aqueous durability, surpassing the limitations of pristine CsPbBr3 PeQDs. This work opens new opportunities for the c-ALD method to be integrated into perovskite core/shell heterostructures for advancing optoelectronic technologies. 2025-07-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59981 Title: Optimizing Charge Balance in Quantum Dot Light-Emitting Diodes through Benzoic Acid-Passivated ZnO Nanoparticle Layers Author(s): Cho, Sinyoung; Ahn, Jae-Hyeon; Choi, Donghyun; Chae, Weon-Sik; Ko, Keum-Jin; Lee, Jong-Soo Abstract: ZnO nanoparticles (ZnO NPs) are widely utilized as electron transport layers (ETLs) in quantum dot light-emitting diodes (QLEDs) due to their high electron mobility, wide bandgap, excellent transparency, and effective hole-blocking properties. However, their high electron mobility can lead to charge imbalance and increased leakage currents, while surface defects contribute to exciton quenching at the interface with the emissive layer (EML), limiting the overall device performance. In this study, 4-CF3BA ligands were employed to effectively passivate surface defects in ZnO NPs, reducing exciton quenching and optimizing charge transport dynamics in QLEDs. This passivation strategy resulted in a significant improvement in device performance, achieving an external quantum efficiency (EQE) of 23%. The performance improvement is attributed to the suppression of interface quenching through defect passivation, improved charge balance, and enhanced electron injection. These findings demonstrate the potential of 4-(trifluoromethyl)benzoic acid (4-CF3BA) passivation as a promising approach to improve the efficiency of QLEDs, opening the way for next-generation optoelectronic device applications. 2025-11-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59036 Title: Hybrid Polyacrylamide-ZnO Electron Transport Layers; Enhancing Exciton Recombination and Charge Injection for High-Efficiency QLEDs Author(s): Ahn, Jae-Hyeon; Cho, Sinyoung; Choi, Donghyun; Chae, Weon-Sik; Song, Myungkwan; Ko, Keum-Jin; Lee, Jong-Soo Abstract: ZnO nanoparticles (ZnO NPs) are widely utilized as electron transport layers (ETLs) in quantum dot light-emitting diodes (QLEDs) due to their high electron mobility, wide bandgap, excellent transparency, and effective hole blocking properties. However, exciton quenching at the interface between quantum dots (QDs) and ZnO NPs and unfavorable band alignment hinder the performance of QLED devices. In this study, a straightforward and versatile approach is introduced to fabricate high-performance QLED by incorporating Polyacrylamide (polyNIPAM) with ZnO NPs. The resulting QD and hybrid-ZnO NPs films achieved a photoluminescence quantum yield (PLQY) of 57.8% and a recombination rate of 80.07%. Compared to conventional ZnO-based QLEDs, the hybrid approach led to a significant improvement in external quantum efficiency (22.34%), maximum brightness (97 593 cd m-2), and a narrow full-width at half maximum (FWHM) of 22.3 nm. The hybrid ZnO NPs exhibited favorable energy levels for electron injection, promoting exciton recombination while minimizing charge diffusion losses at the QD/ZnO NP interfaces. These findings highlight the potential of polyNIPAM-functionalized ZnO NPs for scalable, high-performance QLED fabrication. Future work will focus on optimizing hybrid material composition to further suppress electron leakage and enhance charge transport 1in large-area devices. 2025-09-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58591 Title: Green Solvent Enabled Perovskite Ink for Ambient-Air-Processed Efficient Inkjet-Printed Perovskite Solar Cells Author(s): Satale, Vinayak Vitthal; Chowdhury, Sagnik; Mohamed, Asmaa; Kim, Do-Hyung; Cho, Sinyoung; Lee, Jong-Soo; Kang, Jae-Wook Abstract: Perovskite ink based on a green or non-toxic solvent meets industrial requirements for efficient perovskite solar cells (PSCs). Perovskite inks must be developed with non-toxic or involve the limited use of toxic solvents to fabricate efficient inkjet-printed (IJP) perovskite photovoltaics. Herein, gamma-valerolactone is used as a solvent with a low environmental impact, and the strategy showed category 3 toxicity, even with a small quantity of toxic solvents employed to dissolve the perovskite salts. The structural, optical, and electronic properties of IJP perovskite films are improved by adding 1,3-dimethyl-2-imidazolidinone (DMI) to the green perovskite ink. The IJP perovskite films developed by green solvents with 15% (volume %) of DMI exhibited high thickness uniformity (approximate to 97%), and thicker and smoother surfaces than their counterparts. An additive-modified IJP-PSC device achieved a maximum power conversion efficiency (PCE) of 17.78%, higher than that of an unmodified device (14.75%). The performance of the IJP-PSC device is superior primarily because of its exceptional film-thickness homogeneity, larger grains, and appropriate structures. These attributes significantly decreased unwanted reactions of the perovskite with solvents, ensuring phase purity and enhancing overall efficiency. The innovative green-solvent ink-engineering strategy for producing large-scale perovskite films shows great promise for advancing perovskite solar module technology (with PCE of 13.14%). 2025-09-30T15:00:00Z