https://scholar.dgist.ac.kr/handle/20.500.11750/16007 2026-05-15T02:44:17Z https://scholar.dgist.ac.kr/handle/20.500.11750/60355 Title: A brief review of hot-carrier dynamics in metal halide perovskites: mechanistic insights from time-resolved spectroscopy Author(s): Kim, Bora; Park, Nohyoon; Sung, Jooyoung Abstract: Owing to their slow hot-carrier energy relaxation, metal halide perovskites have emerged as promising candidates for next-generation photovoltaics. This prolonged hot-carrier cooling allows excess energy to be harvested before dissipation as heat, thereby potentially enabling solar cells to exceed the Shockley-Queisser limit. Therefore, elucidating the mechanisms governing hot-carrier cooling is crucial for device optimization. Timeresolved spectroscopy enables observation of these ultrafast processes with high temporal resolution, revealing that intrinsic material properties, including A- and B-site compositions, fundamentally modulate lattice vibrations and electron-phonon coupling strength. Furthermore, structural dimensionality introduces quantum confinement effects that modify the phonon density of states and carrier interactions, while energy-recycling processes, such as phonon reabsorption and Auger-induced carrier reheating, aid in prolonging hot-carrier lifetimes. These mechanistic insights provide a clear understanding of hot-carrier dynamics, which is essential for developing high-efficiency hot-carrier solar cells and advanced optoelectronic devices. https://scholar.dgist.ac.kr/handle/20.500.11750/60352 Title: Anisotropic Strain-Induced Centrosymmetry Breaking in Cubic Formamidinium Lead Iodide (α-FAPbI3) Thin Films Author(s): Jeong, Hyeon Jun; Kim, Bora; Nishikubo, Ryosuke; Wang, Canjie; Song, Jongyoung; In, Yongjae; Han, Seokhun; Gibson, Aedan; Amornkitbamrung, Urasawadee; Wakamiya, Atsushi; Saeki, Akinori; Sung, Jooyoung; Shin, Hyunjung Abstract: Organic-inorganic halide perovskites have emerged as promising materials for next-generation optoelectronic devices due to their exceptional photophysical properties. Among them, alpha-formamidinium lead tri-iodide (alpha-FAPbI3) with a cubic symmetry (space group of ) has garnered attention as a potential absorber in solar cells for its narrow bandgap and superior stability. The fundamental mechanisms governing its high performance have yet to be fully elucidated. In this study, we demonstrate that centrosymmetry breaking in [001] preferentially oriented alpha-FAPbI3 thin films (POF) arises from inevitable anisotropic strain during film formation. Using circular polarization-dependent pump-probe transient absorption spectroscopy, we observe Rashba-type band splitting exclusively in POF, indicating symmetry breaking. Angle-dependent X-ray diffraction and photoluminescence (PL) reveal significant residual stress in POF compared to randomly oriented films (ROF), confirming strain-induced lattice distortion. Furthermore, time-resolved PL and microwave conductivity measurements reveal top-back inhomogeneous carrier dynamics and anisotropic charge carrier mobility, supporting the presence of the anisotropic strain-induced symmetry breaking. Our findings provide direct experimental evidence that inevitable strain in POF induces static Rashba effects, offering new insights into strain engineering for high-performance perovskite optoelectronics and potential quantum applications. https://scholar.dgist.ac.kr/handle/20.500.11750/60351 Title: Flattening Energy Puddles for Enhanced Charge Transport in Wrinkled WSe2 Author(s): Park, Dae Young; Kim, Taehoon; Kim, Bora; Park, Nohyoon; Bang, Seungho; Lee, Dohyeon; Choi, Deogkyu; Kim, Dong Hyeon; Yoo, Jaekak; Lee, Seung Mi; Yu, Young Joo; Jo, Jieun; Song, Jungeun; Ko, Hayoung; Won, Yo Seob; Jeong, Takmo; Yun, Seok Joon; Kim, Ki Kang; Kim, Dong-Wook; Sung, Jooyoung; Jeong, Mun Seok Abstract: Wrinkles, a prevalent form of line defect in monolayer (1L) 2D materials, significantly degrade their optoelectronic performance by inducing local strain, energy puddles, and charge trapping. This study introduces a wrinkle-selective strategy utilizing trioctylphosphine selenide (TOPSe), which exploits its steric hindrance and electron-donating nature to selectively heal selenium vacancies at strained wrinkle sites in 1L-WSe2. Comprehensive spectroscopic characterization-comprising Raman spectroscopy, photoluminescence spectroscopy, and femtosecond transient absorption microscopy-demonstrated substantial reductions in the defect density, suppressed non-radiative recombination, and prolonged exciton lifetimes. Kelvin probe force microscopy further revealed wrinkle-specific electron doping and spatial homogenization of the conduction band. Field-effect transistors based on TOPSe-treated 1L-WSe2 exhibited more than a two-fold increase in current and mobility, in conjunction with a transition from p-type to n-type conduction. Our findings indicate that wrinkle-targeted molecular engineering is a versatile approach for addressing intrinsic inhomogeneities in 2D materials and enabling high-performance optoelectronic devices. https://scholar.dgist.ac.kr/handle/20.500.11750/60045 Title: Impact of trivalent Sb3+-ion doping on charge carrier recombination dynamics of cesium lead bromide perovskite quantum dots Author(s): Jo, Jinwoong; Yu, Jaesang; Kim, Chanwoo; Cho, Inyoung; Lim, Kyeong Mo; Sung, Jooyoung; Oh, Juwon; Yang, Jaesung Abstract: Metal-ion doping of perovskites has proven to enhance their photoluminescence (PL) properties and stability; however, the underlying charge carrier dynamics remain unclear. We synthesized a cesium lead bromide (CsPbBr3) perovskite quantum dot (PQD) incorporating a heterovalent Sb3+ ion dopant and its pristine counterpart and performed time-resolved single-particle PL spectroscopy. The PL intensity and lifetime of the Sb-CsPbBr3 PQD were remarkably enhanced compared to those of the pristine-CsPbBr3 PQD because of diminished nonradiative charge carrier recombination dynamics. The charge carrier trapping (detrapping) rate was lower (higher) for the Sb-CsPbBr3 PQD than for the pristine-CsPbBr3 PQD, as the Sb3+ doping contributed to hindering the formation of the structural defects responsible for charge carrier trap states and increasing the exciton binding energy. The replacement of Pb2+ with Sb3+, which has a smaller ionic radius, in the CsPbBr3 structure effectively increased the tolerance factor, enabling the doped PQD to exhibit more stable local structures and, thus, suppressing its decomposition. 2025-09-30T15:00:00Z