https://scholar.dgist.ac.kr/handle/20.500.11750/210 Sun, 06 Sep 2026 11:59:26 GMT 2026-09-06T11:59:26Z https://scholar.dgist.ac.kr/handle/20.500.11750/60744 Title: Advanced In Situ TEM for Elucidating Structural Evolution and Rational Stability Design in Semiconductor Nanocrystals Author(s): Hyeonjong Ma Description: In situ transmission electron microscopy, liquid-phase TEM, semiconductor nanocrystals, degradation mechanisms, surface and shell engineering, stability Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60744 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60743 Title: Electrochemical Origins and Mitigation of Performance Limitations in Rechargeable Batteries Author(s): Jiyun Jeon Description: Lithium-ion batteries, Overpotential, Resistance, Degradation, Performance limitation Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60743 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60742 Title: All-Solution Processed QLEDs with Improved Charge Balance via Device Structure Engineering Author(s): Jae-Hyeon Ahn Abstract: 본 연구에서는 소자 구조 공학을 통해 전하 균형을 향상시킨 전용액 공정 기반 양자점 발광다이오드를 개발하였다. 콜로이드 양자점 기반 QLED에서 균형 잡힌 전하 주입과 재결합은 소자 효율 및 구동 안정성을 결정하는 핵심 요소이나, 전하 불균형과 계면 여기자 소광은 여전히 주요한 성능 저하 요인으로 작용한다. 이를 해결하기 위해 전자수송층(Electron Transport Layer, ETL)과 정공주입층(Hole Injection Layer, HIL)을 동시에 최적화하는 양방향 계면 제어 전략을 도입하였으며, 이를 통해 전하 수송, 에너지 준위 정렬 및 여기자 재결합 거동을 정밀하게 제어하고자 하였다. 전자 주입층 측면에서는 ZnO 나노입자와 poly(N-isopropylacrylamide)로 구성된 고분자–나노입자 하이브리드 전자수송층을 설계하였다. 하이브리드 ETL은 계면 여기자 소광을 효과적으로 억제하고 전자 누설을 감소시키는 동시에 효율적인 전자 수송 특성을 유지함으로써 전하 균형을 향상시켰다. 그 결과, 최적화된 소자는 최대 외부양자효율 22.34%, 약 22–23 nm의 좁은 반치폭, 그리고 향상된 구동 안정성을 달성하였다. 정공 주입층 측면에서는 NiO 나노입자 기반 HIL에 4-bromomethyl benzoic acid 자가조립단분자막을 도입하여 분자 계면 공학을 구현하였다. 형성된 분자 쌍극자층은 Ni3+ 관련 결함 상태를 감소시키고 에너지 준위 정렬을 개선함으로써 정공 주입을 촉진하였으며, 트랩 보조 비방사성 재결합을 효과적으로 억제하였다. 이에 따라 최적화된 소자는 2.2 V의 낮은 구동 전압, 54,660 cd m⁻²의 최대 휘도, 그리고 최대 EQE 20.34%를 달성하였다. X선 광전자 분광법, 자외선 광전자 분광법, 시간분해 광발광 분광법, 시간분해 전계발광 분석, 임피던스 분광법 등 다양한 분광·전기적 분석을 통해 ETL 및 HIL 계면 제어가 전하 수송을 향상시키고 전하 균형을 개선하며 효율적인 방사 재결합을 촉진함을 확인하였다. 이러한 결과는 양방향 계면 제어 기반의 소자 구조 공학이 고효율·고안정성 전용액 공정 QLED 구현을 위한 효과적인 전략임을 입증한다. 나아가 본 연구는 나노스케일 계면 화학과 실용적 소자 구조 설계를 연결하는 확장 가능한 설계 프레임워크를 제시함으로써 차세대 양자점 기반 광전자소자 개발에 기여할 것으로 기대된다. |This study presents the development of all-solution-processed quantum dot light-emitting diodes (QLEDs) with improved charge balance through device structure engineering. Achieving balanced carrier injection and recombination remains one of the most critical challenges in colloidal QLEDs, as charge imbalance and interfacial exciton quenching significantly limit device efficiency and operational stability. To address these issues, a bidirectional interface engineering strategy was developed by simultaneously optimizing the electron transport layer (ETL) and hole injection layer (HIL), enabling precise control of charge transport, energy-level alignment, and exciton recombination dynamics. For the electron-injection side, a polymer–nanoparticle hybrid ETL composed of ZnO nanoparticles and poly(N-isopropylacrylamide) (polyNIPAM) was designed to regulate interparticle interactions and interfacial energetics. The hybrid ETL effectively suppressed exciton quenching, reduced electron leakage, and enhanced charge balance while maintaining efficient electron transport. As a result, the optimized devices achieved a peak external quantum efficiency (EQE) of 22.34%, narrow electroluminescence spectra (FWHM ≈ 22–23 nm), and improved operational stability. For the hole-injection side, molecular interface engineering was implemented using self-assembled monolayers of 4-bromomethyl benzoic acid (4-BMBA) on NiO nanoparticle-based HILs. The molecular dipole layer simultaneously reduced Ni³⁺-related defect states and improved energy-level alignment, facilitating efficient hole injection and suppressing trap-assisted non-radiative recombination. Consequently, the optimized devices exhibited a low turn-on voltage of 2.2 V, a maximum luminance of 54,660 cd m⁻², and a peak EQE of 20.34%. Comprehensive spectroscopic and electrical characterizations, including X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), time-resolved photoluminescence (TRPL), transient electroluminescence (Tr-EL), and impedance spectroscopy, revealed that both ETL and HIL engineering significantly improved charge transport, enhanced charge balance, and promoted efficient radiative recombination. These results demonstrate that device structure engineering based on bidirectional interface control provides an effective strategy for achieving highly efficient and stable all-solution-processed QLEDs. Furthermore, this work establishes a scalable design framework for next-generation quantum-dot optoelectronics by bridging nanoscale interfacial chemistry with practical device architecture engineering. Keywords: QLED, ZnO, NiO, charge balance, exciton quenching, interfacial resistance Description: QLED, ZnO, NiO, charge balance, exciton quenching, interfacial resistance Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60742 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60741 Title: Band Structure Engineering for Optimal Optoelectronic Device Author(s): Sang-Hyeon Lee Description: 2D materials, Optoelectric device, Low-dimensional materials, Tunneling device, Computational Spectrometer, Defect engineering Wed, 31 Dec 2025 15:00:00 GMT https://scholar.dgist.ac.kr/handle/20.500.11750/60741 2025-12-31T15:00:00Z