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Article A Benchmark of Expert-Level Academic Questions to Assess AI Capabilities(Nature Portfolio, 2026) Phan, Long; Gatti, Alice; Li, Nathaniel; Khoja, Adam; Kim, Ryan; Ren, Richard; Scaramuzza, Davide; Park, JongeeBenchmarks are important tools for tracking the rapid advancements in large language model (LLM) capabilities. However, benchmarks are not keeping pace in difficulty: LLMs now achieve more than 90% accuracy on popular benchmarks such as Measuring Massive Multitask Language Understanding(1), limiting informed measurement of state-of-the-art LLM capabilities. Here, in response, we introduce Humanity's Last Exam (HLE), a multi-modal benchmark at the frontier of human knowledge, designed to be an expert-level closed-ended academic benchmark with broad subject coverage. HLE consists of 2,500 questions across dozens of subjects, including mathematics, humanities and the natural sciences. HLE is developed globally by subject-matter experts and consists of multiple-choice and short-answer questions suitable for automated grading. Each question has a known solution that is unambiguous and easily verifiable but cannot be quickly answered by internet retrieval. State-of-the-art LLMs demonstrate low accuracy and calibration on HLE, highlighting a marked gap between current LLM capabilities and the expert human frontier on closed-ended academic questions. To inform research and policymaking upon a clear understanding of model capabilities, we publicly release HLE at https://lastexam.ai.Article Citation - WoS: 10Alkaline Hydrothermal Synthesis, Characterization, and Photocatalytic Activity of Tio2 Nanostructures: the Effect of Initial Tio2 Phase(Amer Scientific Publishers, 2019) Erdogan, Nursev; Park, Jongee; Choi, Woohyuk; Kim, Soo Young; Ozturk, AbdullahOne-dimensional (1D) titanate nanostructures were synthesized by hydrothermal route, using commercially available TiO2 (P25) and anatase powders as precursor materials and strong NaOH solution as catalyzer. The prepared titanates were calcined, followed by protonation to produce TiO2 nanostructures having enhanced photocatalytic and photovoltaic properties. The synthesized TiO2 1D nanostructures were characterized using field-emission scanning electron microscope, high-resolution electron microscope, X-ray diffraction analysis, and UV-Vis photospectroscopy to understand the effect of initial TiO2 phase on morphological and crystallographic features, and bandgap. Methylene blue degradation test was applied to evaluate the photoactivity of the products obtained after different stages of the process. The findings indicate that 1D TiO2 nanostructures form by different mechanisms from dissolved aggregates during hydrothermal process, depending on the crystal structure of the initial precursor used. Photocatalytic test results reveal that protonated titanates have considerable adsorption capability, while photocatalytic degradation depends on TiO2 transformation.Article Calcium Phosphate Honeycomb Scaffolds With Tailored Microporous Walls Using Phase Separation-Assisted Digital Light Processing(MDPI, 2025) Kim, Gyu-Nam; Park, Jae-Hyung; Song, Jae-Uk; Koh, Young-Hag; Park, JongeeThe present study reports on the manufacturing of biphasic calcium phosphate (BCP) honeycomb scaffolds with tailored microporous walls using phase separation-assisted digital light processing (PS-DLP). To create micropores in BCP walls, camphene was used as the pore-forming agent for preparing BCP suspensions, since it could be completely dissolved in photopolymerizable monomers composed of triethylene glycol dimethacrylate (TEGDMA) and polyethylene glycol diacrylate (PEGDA) and then undergo phase separation when placed at 5 degrees C. Therefore, solid camphene crystals could be formed in phase-separated BCP layers and then readily removed via sublimation after the photopolymerization of monomer networks embedding BCP particles by DLP. This approach allowed for tight control over the microporosity of BCP walls by adjusting the camphene content. As the camphene content increased from 40 to 60 vol%, the microporosity increased from similar to 38 to similar to 59 vol%. Consequently, the overall porosity of dual-scale porosity scaffolds increased from similar to 51 to similar to 67 vol%, while their compressive strength decreased from similar to 70.4 to similar to 13.7 MPa. The mass transport ability increased remarkably with an increase in microporosity.Article Citation - WoS: 23Citation - Scopus: 27Facile synthesis of CsPbBr3/PbSe composite clusters(Taylor & Francis Ltd, 2018) Thang Phan Nguyen; Ozturk, Abdullah; Park, Jongee; Sohn, Woonbae; Tae Hyung Lee; Jang, Ho Won; Kim, Soo Young; Nguyen, Thang Phan; Lee, Tae HyungIn this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs: Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots.Article Citation - WoS: 6Citation - Scopus: 6Diethanolamine Modified Perovskite-Substrate Interface for Realizing Efficient Esl-Free Pscs(Mdpi, 2023) Sajid, Sajid; Alzahmi, Salem; Wei, Dong; Ben Salem, Imen; Park, Jongee; Obaidat, Ihab M.; Salem, Imen BenSimplifying device layout, particularly avoiding the complex fabrication steps and multiple high-temperature treatment requirements for electron-selective layers (ESLs) have made ESL-free perovskite solar cells (PSCs) attractive. However, the poor perovskite/substrate interface and inadequate quality of solution-processed perovskite thin films induce inefficient interfacial-charge extraction, limiting the power conversion efficiency (PCEs) of ESL-free PSCs. A highly compact and homogenous perovskite thin film with large grains was formed here by inserting an interfacial monolayer of diethanolamine (DEA) molecules between the perovskite and ITO substrate. In addition, the DEA created a favorable dipole layer at the interface of perovskite and ITO substrate by molecular adsorption, which suppressed charge recombination. Comparatively, PSCs based on DEA-treated ITO substrates delivered PCEs of up to 20.77%, one of the highest among ESL-free PSCs. Additionally, this technique successfully elongates the lifespan of ESL-free PSCs as 80% of the initial PCE was maintained after 550 h under AM 1.5 G irradiation at ambient temperature.Article Citation - WoS: 20Citation - Scopus: 24Lead-Free Perovskite Homojunction-Based Htm-Free Perovskite Solar Cells: Theoretical and Experimental Viewpoints(Mdpi, 2023) Sajid, Sajid; Alzahmi, Salem; Salem, Imen Ben; Park, Jongee; Obaidat, Ihab M.Simplifying the design of lead-free perovskite solar cells (PSCs) has drawn a lot of interest due to their low manufacturing cost and relative non-toxic nature. Focus has been placed mostly on reducing the toxic lead element and eliminating the requirement for expensive hole transport materials (HTMs). However, in terms of power conversion efficiency (PCE), the PSCs using all charge transport materials surpass the environmentally beneficial HTM-free PSCs. The low PCEs of the lead-free HTM-free PSCs could be linked to poorer hole transport and extraction as well as lower light harvesting. In this context, a lead-free perovskite homojunction-based HTM-free PSC was investigated, and the performance was then assessed using a Solar Cell Capacitance Simulator (SCAPS). A two-step method was employed to fabricate lead-free perovskite homojunction-based HTM-free PSCs in order to validate the simulation results. The simulation results show that high hole mobility and a narrow band gap of cesium tin iodide (CsSnI3) boosted the hole collection and absorption spectrum, respectively. Additionally, the homojunction's built-in electric field, which was identified using SCAPS simulations, promoted the directed transport of the photo-induced charges, lowering carrier recombination losses. Homojunction-based HTM-free PSCs having a CsSnI3 layer with a thickness of 100 nm, defect density of 10(15) cm(-3), and interface defect density of 10(18) cm(-3) were found to be capable of delivering high PCEs under a working temperature of 300 K. When compared to formamidinium tin iodide (FASnI(3))-based devices, the open-circuit voltage (V-oc), short-circuit density (J(sc)), fill factor (FF), and PCE of FASnI(3)/CsSnI3 homojunction-based HTM-free PSCs were all improved from 0.66 to 0.78 V, 26.07 to 27.65 mA cm(-2), 76.37 to 79.74%, and 14.62 to 19.03%, respectively. In comparison to a FASnI(3)-based device (PCE = 8.94%), an experimentally fabricated device using homojunction of FASnI(3)/CsSnI3 performs better with V-oc of 0.84 V, J(sc) of 22.06 mA cm(-2), FF of 63.50%, and PCE of 11.77%. Moreover, FASnI(3)/CsSnI3-based PSC is more stable over time than its FASnI(3)-based counterpart, preserving 89% of its initial PCE. These findings provide promising guidelines for developing highly efficient and environmentally friendly HTM-free PSCs based on perovskite homojunction.
