Physics / Fizik
Permanent URI for this collectionhttps://hdl.handle.net/11147/6
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Article Citation - WoS: 2Citation - Scopus: 2Highly Mobile Excitons in Single Crystal Methylammonium Lead Tribromide Perovskite Microribbons(American Chemical Society, 2022) McClintock, Luke; Song, Ziyi; Travaglini, H. Clark; Senger, Ramazan Tuğrul; Chandrasekaran, Vigneshwaran; Htoon, Han; Yarotski, Dmitry; Yu, DongExcitons are often given negative connotation in solar energy harvesting in part due to their presumed short diffusion lengths. We investigate exciton transport in single-crystal methylammonium lead tribromide (MAPbBr3) microribbons via spectrally, spatially, and temporally resolved photocurrent and photoluminescence measurements. Distinct peaks in the photocurrent spectra unambiguously confirm exciton formation and allow for accurate extraction of the low temperature exciton binding energy (39 meV). Photocurrent decays within a few μm at room temperature, while a gate-tunable long-range photocurrent component appears at lower temperatures (about 100 μm below 140 K). Carrier lifetimes of 1.2 μs or shorter exclude the possibility of the long decay length arising from slow trapped-carrier hopping. Free carrier diffusion is also an unlikely source of the highly nonlocal photocurrent, due to their small fraction at low temperatures. We attribute the long-distance transport to high-mobility excitons, which may open up new opportunities for novel exciton-based photovoltaic applications.Article Citation - WoS: 2Citation - Scopus: 3Transport Modeling of Locally Photogenerated Excitons in Halide Perovskites(American Chemical Society, 2021) Tang, Kuen Wai; Li, Senlei; Weeden, Spencer; Song, Ziyi; McClintock, Luke; Xiao, Rui; Senger, Ramazan TuğrulExcitons have fundamental impacts on optoelectronic properties of semiconductors. Halide perovskites, with long carrier lifetimes and ionic crystal structures, may support highly mobile excitons because the dipolar nature of excitons suppresses phonon scattering. Inspired by recent experimental progress, we perform device modeling to rigorously analyze exciton formation and transport in methylammonium lead triiodide under local photoexcitation by using a finite element method. Mobile excitons, coexisting with free carriers, can dominate photocurrent generation at low temperatures. The simulation results are in excellent agreement with the experimentally observed strong temperature and gate dependence of carrier diffusion. This work signifies that efficient exciton transport can substantially influence charge transport in the family of perovskite materials.Article Citation - WoS: 16Citation - Scopus: 16Temperature and Gate Dependence of Carrier Diffusion in Single Crystal Methylammonium Lead Iodide Perovskite Microstructures(American Chemical Society, 2020) McClintock, Luke; Xiao, Rui; Hou, Yasen; Gibson, Clinton; Travaglini, Henry Clark; Abramovitch, David; Tan, Liang Z.; Senger, Ramazan Tuğrul; Fu, Yongping; Jin, SongWe investigate temperature-dependent photogenerated carrier diffusion in single-crystal methylammonium lead iodide microstuctures via scanning photocurrent microscopy, Carrier diffusion lengths increased abruptly across the tetragonal to orthorhombic phase transition and reached 200 +/- 50 mu m at 80 K. In combination with the microsecond carrier lifetime measured by a transient photocurrent method, an enormous carrier mobility value of 3 x 10(4) cm(2)/V s was extracted at 80 K. The observed highly nonlocal photocurrent and the rapid increase of the carrier diffusion length at low temperatures can be understood by the formation and efficient transport of free excitons in the orthorhombic phase as a result of reduced optical phonon scattering due to the dipolar nature of the excitons. Carrier diffusion lengths were tuned by a factor of 8 by gate voltage and increased with increasing majority carrier (electron) concentration, consistent with the exciton model.Article Citation - WoS: 22Citation - Scopus: 22Zinc Oxide and Metal Halide Perovskite Nanostructures Having Tunable Morphologies Grown by Nanosecond Laser Ablation for Light-Emitting Devices(American Chemical Society, 2020) Demirci Sankir, Nurdan; Abdullayeva, Nazrin; Altaf, Çiğdem Tuç; Kumtepe, Alihan; Yılmaz, Nazmi; Coşkun, Özlem; Sankir, Mehmet; Kurt, Hamza; Çelebi, Cem; Yanılmaz, AlperThis work reports a one-pot chemical bath deposition (CBD) method for the preparation of selectively grown, morphology-tunable zinc oxide (ZnO) nanostructures provided via straightforward nanosecond fiber laser ablation. Nanosecond fiber laser ablation is different from lithographic methods due to its simple, time saving, and efficient film scribing abilities. Here, multiple morphologies of the ZnO nanostructures on the same substrate have been grown via laser ablation of the ZnO seeding layer. Selective and controlled ablation of the titanium layer, ZnO growth inhibitor, resulted in systematic growth of nanorod arrays, while the application of extensive fluence energies resulted in the penetration of the laser beam until the glass substrate induced the nanoflake growth within the same CBD environment. The laser penetration depth has been numerically investigated via COMSOL Multiphysics heat module simulations, and the optical variations between two nanostructures (nanorod and nanoflake) have been examined via Lumerical FDTD. The simultaneous growth of two morphologies served as an efficient tool for the enhancement of photoluminescence intensities. It increased the average charge carrier lifetimes of the thin films from approximately 2.01 to 9.07 ns under the same excitation wavelengths. The amplification in PL performances has been accomplished via the capstone of all-inorganic halide perovskite (IHP) deposition that brought a successful conclusion to lifetime responses, which have been increased by 1.4-fold. The development of IHP sensitized nanoscaled multimorphological ZnO thin films can, therefore, be used as potential nanomaterials for light-emitting-device applications. © 2020 American Chemical Society.