Article
Physics, Applied
M. Tyunina, M. Savinov, A. Dejneka
Summary: In ABO(3) perovskite oxide ferroelectrics, the study focused on the small-polaron hopping conductivity in thin films, showing significant increase in activation energy with temperature due to strong electron-phonon coupling and complex lattice oscillations. The lack of clear relations between activation energy and microstructure, composition, or phase transitions emphasized the critical role of phonons in the conductivity of ferroelectric films. The presence of strong electron-phonon coupling, rich phonon ensembles, and coexistence of phonon-stimulated and phonon-less processes suggests a highly variable small-polaron conductivity in ferroelectric films, which warrants further studies.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Mateusz Dyksik, Dorian Beret, Michal Baranowski, Herman Duim, Sebastien Moyano, Katarzyna Posmyk, Adnen Mlayah, Sampson Adjokatse, Duncan K. Maude, Maria Antonietta Loi, Pascal Puech, Paulina Plochocka
Summary: The authors investigate the optical response of 2D layered perovskites and observe the presence of phonon replicas. They also observe a high-frequency signal with spectral fingerprints of polarons and characterize the polaron vibronic progression. The understanding of polaronic effects in perovskites is important for future opto-electronic applications.
Article
Optics
R. R. Akhmadullin, N. V. Kozyrev, B. R. Namozov, Yu. G. Kusrayev, G. Karczewski, T. Wojtowicz
Summary: This paper investigates the energy and spin relaxation of excitons and trions in (Cd, Mn)Te/(Cd, Mg)Te quantum wells containing hole magnetic polarons using polarized photoluminescence technique. The results show that the photoluminescence is polarized under circularly polarized photoexcitation, indicating the presence of spin memory in these systems. It is suggested that the long spin memory is due to the formation of magnetic polarons stabilizing the spin of excitons. Additionally, an inverted sign of circular polarization degree is observed in the radiation spectrum under quasiresonant excitation of trion states, indicating a special spin relaxation mechanism. The application of an external magnetic field leads to depolarization of excitonic radiation, caused by destabilization of magnetic polarons and shortened spin relaxation time of excitons.
JOURNAL OF LUMINESCENCE
(2023)
Article
Materials Science, Multidisciplinary
Angelica Simbula, Riccardo Pau, Qingqian Wang, Fang Liu, Valerio Sarritzu, Stefano Lai, Matteo Lodde, Francesco Mattana, Guido Mula, Alessandra Geddo Lehmann, Ioannis D. Spanopoulos, Mercouri G. Kanatzidis, Daniela Marongiu, Francesco Quochi, Michele Saba, Andrea Mura, Giovanni Bongiovanni
Summary: Rapid advancements in perovskite photovoltaics have led to the production of efficient solar cells with improved stability and duration, primarily due to changes in materials composition and photophysics. The presence of unbound charge carrier plasmas, even in 2D perovskites at cryogenic temperatures, suggests potential novel mechanisms for LEDs and lasers, as well as highlighting the significant role of 2D perovskites in photovoltaics.
ADVANCED OPTICAL MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Koloman Wagner, Zakhar A. Iakovlev, Jonas D. Ziegler, Marzia Cuccu, Takashi Taniguchi, Kenji Watanabe, Mikhail M. Glazov, Alexey Chernikov
Summary: This study demonstrates the diffusion of excitons in a monolayer semiconductor with a continuously tunable Fermi sea of free charge carriers. The light emission from tightly bound exciton states in electrically gated WSe2 monolayer is detected using microscopy. The measurements reveal a nonmonotonic dependence of the exciton diffusion coefficient on the charge carrier density.
Article
Materials Science, Multidisciplinary
Ayushi Tripathi, Yoonjoo Lee, Changhwa Jung, Soohyun Kim, Soonyong Lee, Woojin Choi, Chaeyeon Park, Young Wan Kwon, Hyunjung Lee, Han Young Woo
Summary: A new donor-donor (D-D')-type polymer (PIDTSCDTS) with extended pi-conjugation and pronounced chain planarity is synthesized by substituting sp(2)-hybridized alkenyl side chains with electron-rich indacenodithiophene (IDT) and cyclopentadithiophene (CDT) moieties. The thermoelectric (TE) properties of the polymer are studied with different doping methods, revealing that hybrid doping (HyD) achieves a higher conductivity (sigma) of up to 500 S cm(-1) due to enhanced (bi)polaron generation. Analysis of the Seebeck coefficient (S) and conductivity (sigma) relationship shows metal-like carrier transport in polymers obtained via sequential doping (SqD) and HyD, resulting in a larger maximum power factor (PFmax) of about 40 mu W m(-1) K-2 compared to SqD films. Careful consideration of degenerate doping and band-like carrier transport is needed for further optimizing the TE properties.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Chemistry, Physical
Mohammad Balooch Qarai, Raja Ghosh, Frank C. Spano
Summary: The Holstein-based model has been expanded to include singlet bipolarons in conjugated polymers with nondegenerate ground states. The mid-IR band for bipolarons is red-shifted by up to 0.2 eV compared to single polarons, reflecting enhanced hole delocalization in the bound bipolaron complex. This observation is in good agreement with recent measurements on electrochemically doped P3HT.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Review
Physics, Multidisciplinary
Gianluca Tirimbo, Bjorn Baumeier
Summary: Excitons, important for both fundamental optical properties and functionality in opto-electronic devices, come in various forms depending on the material they are created in, presenting challenges for ab initio modeling. Utilizing GW approximation and BSE equation, our recent work addresses the embedding of this method into multi-method models for organic materials, highlighting current challenges and providing examples from organic photovoltaics and fluorescence spectroscopy towards future studies.
ADVANCES IN PHYSICS-X
(2021)
Article
Chemistry, Physical
Anton Matthijs Berghuis, T. Raziman, Alexei Halpin, Shaojun Wang, Alberto G. Curto, Jaime Gomez Rivas
Summary: Using diffraction-limited ultrafast imaging techniques, the study investigated the propagation of singlet and triplet excitons in single-crystal tetracene, revealing a narrowing distribution of singlet excitons after photoexcitation. This narrowing led to a negative diffusion effect where singlet excitons migrated towards high-density regions, ultimately resulting in a distribution smaller than the laser excitation spot. Modeling of the excited-state dynamics attributed this anomalous diffusion to nonlinear triplet-triplet annihilation (TTA), which may have broad implications for studying exciton diffusion and TTA rates in semiconductors relevant to organic optoelectronics.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Bong Lim Suh, Goun Kang, Sun Mi Yoon, Sanghyun Cho, Myoung-Woon Moon, Yun-Mo Sung, Min-Seok Kim, Kahyun Hur
Summary: This study proposes a solution-based dimension control strategy for the fabrication of copper chloride thiourea (CuCl-TU) coordination polymers, enabling the formation of centimeter-scale, 2D nanosheets for transparent electrodes. Despite the wide bandgap, the 2D nanosheet exhibits high electrical conductivity at room temperature without intentional doping. By substituting different thiourea candidates, it is possible to design CuCl-TU structures with desired functionality and stability, expanding the applicability of transparent conducting materials.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Physical
Alberto Privitera, Jeannine Gruene, Akchheta Karki, William K. Myers, Vladimir Dyakonov, Thuc-Quyen Nguyen, Moritz K. Riede, Richard H. Friend, Andreas Sperlich, Alexander J. Gillett
Summary: This study investigates the formation mechanism of triplet excitons in organic solar cells, revealing differences in triplet formation between fullerene and nonfullerene acceptor systems. Engineering good donor and acceptor domain purity is crucial for suppressing losses via triplet excitons in OSCs.
ADVANCED ENERGY MATERIALS
(2022)
Article
Chemistry, Physical
Kyriacos Georgiou, Kirsty E. McGhee, Rahul Jayaprakash, David G. Lidzey
Summary: Researchers have fabricated organic semiconductor microcavities containing J-aggregates of a cyanine dye with an extended optical path-length, and studied the structures using optical-reflectivity, finding a transition from normal strong coupling to decoupled photon-modes by changing the effective oscillator strength within the cavity. Both coupled and decoupled structures were compared in terms of the distribution of the confined optical field using an eight-level modified Hamiltonian.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Physics, Multidisciplinary
T. Dieterle, M. Berngruber, C. Hoelzl, R. Loew, K. Jachymski, T. Pfau, F. Meinert
Summary: The study investigates the transport dynamics of a single low-energy ionic impurity in a Bose-Einstein condensate by implanting the impurity using fast electric field pulses. The results show diffusive transport properties of the impurity and allow for the measurement of its mobility through comparison with simulations. This research opens up a new path for studying dynamics of charged quantum impurities in ultracold matter.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Multidisciplinary
Pietro Massignan, Nikolay Yegovtsev, Victor Gurarie
Summary: The study shows that in a strongly interacting Bose gas, the quasiparticle properties of a heavy Bose polaron depend on the impurity-boson potential through a single parameter that characterizes its range.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Condensed Matter
Jedrzej Szmytkowski
Summary: In this work, a theoretical model is formulated to explain the excitonic Auger process and trap-assisted recombination in two-dimensional monolayer materials. This explanation is crucial for understanding the excitonic and photoelectrical processes in such materials.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Article
Chemistry, Physical
Xin Chang, Mohammad Balooch Qarai, Frank C. Spano
Summary: A vibronic exciton model was developed to explain the spectral signatures of HJ-aggregates in oligomers and polymers with donor-acceptor-donor repeat units. The model shows that single chains with enhanced intrachain order exhibit J-behavior, while positive H-promoting interchain Coulomb interactions in aggregates attenuate the vibronic ratio. The ratio formula derived previously for P3HT aggregates was shown to also apply to (DAD)(N) aggregates with slight modifications.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Raja Ghosh, Francesco Paesani
Summary: The Holstein model for polarons was used to investigate the relationship among defects, topology, Coulomb trapping, and polaron delocalization in COFs, showing that intrasheet topological connectivity and pi-column density can enhance polaron migration significantly. Trigonal COFs are ideal for charge transport, and controlling nanoscale defects and the location of the counteranion is critical for designing new COF-based materials with higher mobilities. Design strategies for enhanced conductivity in COFs can be generalized to other conductive materials such as metal-organic frameworks and perovskites.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Shuwen Yue, Marc Riera, Raja Ghosh, Athanassios Z. Panagiotopoulos, Francesco Paesani
Summary: Building upon previous work, this study introduces a second generation of data-driven many-body models for CO2 and systematically assesses the impact of CO2-CO2 interactions on the models' ability to predict equilibrium properties. By fitting reference energies calculated at the coupled cluster level, a series of models are constructed. The use of charge model 5 and scaling of two-body energies lead to more accurate descriptions of CO2 properties. The findings highlight the importance of training set quality in developing transferable, data-driven models.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
April L. Bialas, Frank C. Spano
Summary: Excimers are commonly found in many organic systems, with broad, structureless, and red-shifted emission. A theoretical model based on a Holstein-Peierls Hamiltonian is proposed to explain absorption and photoluminescence in molecular dimers, showing that excimer emission can be induced through local or nonlocal intermolecular coupling. Incorporating both types of coupling successfully reproduces absorption and excimer emission spectra.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Mohammad Balooch Qarai, Raja Ghosh, Frank C. Spano
Summary: The Holstein-based model has been expanded to include singlet bipolarons in conjugated polymers with nondegenerate ground states. The mid-IR band for bipolarons is red-shifted by up to 0.2 eV compared to single polarons, reflecting enhanced hole delocalization in the bound bipolaron complex. This observation is in good agreement with recent measurements on electrochemically doped P3HT.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Nanoscience & Nanotechnology
Adam J. Moule, Goktug Gonel, Tucker L. Murrey, Raja Ghosh, Jan Saska, Nikolay E. Shevchenko, Ilaria Denti, Alice S. Fergerson, Rachel M. Talbot, Nichole L. Yacoub, Mark Mascal, Alberto Salleo, Frank C. Spano
Summary: Molecular doping of conjugated polymers leads to bleaching of neutral absorbance and the emergence of new polaron absorbance transitions. Analysis of diketopyrrolopyrrole (DPP) co-polymers with ultra-high electron affinity dopants shows saturation of polaron mole fraction, with systematic changes in peak ratios for both neutral and polaron peaks. The study also reveals nonlinear growth of the lowest energy polaron peak with increasing polaron mole fraction, indicating enhanced polarization/delocalization.
ADVANCED ELECTRONIC MATERIALS
(2022)
Correction
Chemistry, Physical
Nicholas J. Hestand, Chenyu Zheng, Anirudh Raju Penmetcha, Brandon Cona, Jeremy A. Cody, Frank C. Spano, Christopher J. Collison
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Xin Chang, Mohammad Balooch Qarai, Frank C. Spano
Summary: A vibronic exciton model is used to describe low-energy electronic excitations in slip-stack aggregates. The study reveals that J- and H-aggregate behavior in these aggregates is driven by intermolecular charge transfer rather than Coulomb coupling as assumed in the Kasha model. Additionally, both J- and H-aggregates exhibit red-shifted behavior.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Correction
Chemistry, Physical
Xin Chang, Mohammad Balooch Qarai, Frank C. Spano
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Raja Ghosh, Francesco Paesani
Summary: Photoactive organic and hybrid organic-inorganic materials exhibit interesting photophysical properties upon interaction with light. A theoretical model that accurately describes the structure-photophysics-property relationships is crucial for understanding these materials. This perspective introduces a unified theoretical framework and discusses excitonic and polaronic photophysical signatures in different materials using the Multiparticle Holstein Formalism. The integration of advanced computational methods with the Multiparticle Holstein Formalism is expected to identify new design strategies for next-generation energy materials.
Article
Chemistry, Physical
Mohammad Balooch Qarai, Raja Ghosh, Nicholas J. Hestand, Frank C. Spano
Summary: Theoretical investigation of multipolaron complexes in p-doped poly(3-hexylthiophene) films, where stationary dopant anions are positioned on both sides of the polymer chain within the lamellar region, was conducted. Complexes as large as tetrapolarons, consisting of four anions and an equal number of mobile holes, were considered. It was found that the mid-IR absorption band (P1) red-shifts and the hole ionization potential decreases as the complex grows in size, from a single polaron to a tetrapolaron. This behavior mainly arises from enhanced hole delocalization due to hole-hole repulsion and has significant implications for charge transport in organic materials.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Physical
Yuanhui Pan, Ching-Hwa Ho, Francesco Paesani, Raja Ghosh
Summary: Covalent organic frameworks (COFs) are 2D organic materials with unique electronic and transport properties. In this study, the impact of interlayer stacking arrangements on the electronic structure and coherence of polarons in donor-acceptor COFs was investigated through density functional theory and multiparticle Holstein formalism simulations. It was found that the stacking arrangement significantly influences the transport properties, with varying behavior from metallic to highly localized states. The extent of charge delocalization is sensitive to the type and precise arrangement of interlayer stacking and donor-acceptor fragments in the COF structure. The results suggest that interlayer interactions can aid in enhancing charge delocalization and guide the design of new COF structures for potential applications in organic electronics.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Garrett Lecroy, Raja Ghosh, Viktoriia Untilova, Lorenzo Guio, Kevin H. Stone, Martin Brinkmann, Christine Luscombe, Frank C. Spano, Alberto Salleo
Summary: This study provides experimental data on the polarized intermolecular and intramolecular absorption of polarons in the polymer semiconductor rr-P3HT. The data is inconsistent with predictions based on the Born-Oppenheimer approximation, but consistent with a modified Holstein Hamiltonian. This work demonstrates the importance of vibronic coupling in understanding polaron absorption.
MATERIALS HORIZONS
(2023)
Article
Chemistry, Multidisciplinary
Raja Ghosh, Francesco Paesani
Summary: This study quantitatively characterizes the complex interplay between electronic defects, domain sizes, pore volumes, chemical dopants, and three-dimensional anisotropic charge migration in 2D COFs, comparing simulations with recent experiments on doped COF films. Our findings highlight fundamental differences between the microstructure, spectral signatures, and transport physics of polymers and COFs. The research also proposes new directions to address existing limitations and improve charge transport in COFs for applications in functional molecular electronic devices.