https://scholar.dgist.ac.kr/handle/20.500.11750/10014 2026-11-11T11:27:25Z https://scholar.dgist.ac.kr/handle/20.500.11750/61123 Title: Noncovalently functionalized conjugated polymers with conjugation-headed poly(ethylene glycol) as efficient hole-transport materials for nanocrystal photovoltaics Author(s): Lee, Ji Hyeon; Kim, Hae Jeong; Shim, Eun Soo; You, Hyung Ryul; 김민영; Ahn, Hyungju; Jang, Hyoik; Lee, Eunho; Choi, Jongmin; Jo, Jea Woong Abstract: Conjugated polymers (CPs) are demanding charge transport materials for various optoelectronic applications. To realize optimized characteristics of CPs for high-performance optoelectronic devices, their molecular ordering and interactions of CPs should be modulated by functionalizing conjugated backbones and side chains. However, typical covalent functionalization requires complicated and multiple syntheses and sometimes provides an unwanted deterioration of intrinsic charge transport properties of CPs. Here, we report a facile functionalization approach for CPs, which possibly affords enhanced charge carrier delivery with suppressed charge recombination, by incorporating a conjugation-headed surfactant (CHS). We found that the CHS effectively generates noncovalent functionalization on the conjugated backbone of CP through pi-pi interaction. Through comparisons using an surfactant without a conjugation-head, the CHS was revealed to be homogeneously and effectively mixed with CP, synergistically improving the morphological and crystal properties of CP films. Therefore, CPs functionalized with the CHS showed improved capabilities as hole-transport materials for nanocrystal photovoltaics; therefore, the corresponding devices recorded high efficiencies of >8% and > 13% in AgBiS2 and PbS nanocrystal photovoltaics, respectively. 2026-11-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/61116 Title: Intermediate-mediated anion tuning of AgIn(S,Te)2 nanorods for highly efficient NIR-II photoluminescence Author(s): Kwon, Ga Yeon; 유도헌; Byun, Jong Chan; Jo, Jea Woong; Choi, Jongmin; Choi, Min-Jae Abstract: Ag-In-Te-based nanocrystals are promising non-toxic emitters for near-infrared-II (NIR-II) photoluminescence (PL), but their efficiency is limited by poor surface passivation and the resulting nonradiative recombination. Here, we report an intermediate-mediated synthesis of anion-tuned AgIn(S,Te)2 nanorods. Ag-In-Sx intermediates serve as reactive precursors, enabling S/Te anion tuning during Te-mediated nanorod growth. The photoluminescence quantum yield (PLQY) tracks the residual sulfide retained within the nanorods and is maximized not under the most Te-rich condition, but at an intermediate composition of 66 at% Te and 34 at% S. The retained sulfide is proposed to form local wide-bandgap Ag-In-S-like environments that may contribute to the suppression of nonradiative recombination while preserving NIR-II emission. The optimized pristine nanorods reach a PLQY of 40.2%, which increases to 62.0% after ZnS surface passivation. The AgIn(S,Te)2@ZnS nanorods were further integrated as the photoactive layer in a photodiode device, showing a distinct NIR photoresponse at wavelengths above 800 nm. These results establish Ag-In-Sx intermediate chemistry as an effective route to control anion composition and enhance NIR-II PL in Te-based nanocrystals. 2026-09-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/61109 Title: Dimensional Phase Reconstruction in 2D/3D Perovskite Solar Cells: Stability Implications Under Thermal, Light, and Bias Stresses Author(s): Kim, Soo-Kwan; Lim, Soohwan; Son, Sung Yun; Choi, Jongmin Abstract: Two-dimensional/three-dimensional (2D/3D) perovskite heterostructures have emerged as a promising strategy to enhance the stability of halide perovskite solar cells (PSCs), entailing an efficient energy landscape and defect-passivation capabilities of the 2D perovskite layer. However, mounting experimental evidence shows that the 2D/3D phase interface is not a static structural entity, but rather a dynamic system susceptible to operational stresses. In this review, we systematically examine how thermal exposure, sustained illumination, and applied bias drive counter-directional interdiffusion of spacer cations and A-site cations across the 2D/3D interface, inducing a gradual increase in the dimensionality (n-value) of the 2D perovskite layer. This stress-induced 2D phase reconstruction erodes the photoactive 3D perovskite domains, disrupts the interfacial funneling energy landscape, and compromises the surface moisture barrier, collectively accelerating device degradation. We further survey emerging mitigation strategies, including polymer interlayers, steric and reactivity engineering of spacer cations, and n-value-tailored Dion-Jacobson frameworks. Finally, we outline critical unresolved challenges and future research directions toward achieving stable 2D/3D perovskite photovoltaics. 2026-08-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/60953 Title: Facile synthesis of large-Stokes-shift giant CdHgSe/CdHgSeS near-infrared quantum dots via chlorine-mediated Ostwald ripening Author(s): Lee, Gyudong; Park, Sanghwang; Seo, Jongcheol; Lee, Wonseok; Arogundade, Opeyemi H.; Smith, Andrew M.; Choi, Jongmin; Choi, Hongsoo; Lim, Sung Jun Abstract: Giant core/shell quantum dots (GQDs) offer advantages for optoelectronics, including suppressed blinking and reduced Auger recombination, yet thick-shell growth often requires laborious successive ion layer adsorption and reaction (SILAR) cycles. Here we demonstrate a chlorine-mediated controlled Ostwald ripening strategy that transforms NIR-emitting CdHgSe/CdS core/shell seed QDs into giant CdHgSe/CdHgSeS core/gradient-shell QDs in a single post-synthetic step. Seed QDs are prepared by growing a thin (similar to 1.6-monolayer) CdS shell on CdHgSe alloy cores. Injection of CHCl3 at 240 degrees C triggers rapid ripening, in which most seeds dissolve while a minor population grows into GQDs. During ripening, the band-edge absorption feature is strongly attenuated and absorption below similar to 610 nm increases markedly, whereas NIR emission remains centered near similar to 900 nm, yielding a large effective Stokes shift that can mitigate reabsorption in luminescent solar concentrators. HAADF-STEM/EDS and XRD support a compositionally graded shell, while mass spectrometry and numerical simulations are consistent with chlorine-modified surface chemistry and altered monomer solubility/surface tension that accelerate ripening. As a proof of concept, embedding the GQDs in PMMA affords a transparent luminescent solar concentrator prototype with retained NIR emission and favorable spectral overlap with silicon photovoltaics. 2026-07-31T15:00:00Z