Article
Chemistry, Multidisciplinary
Lixuan Liu, Zhixiang Wei, Stefan C. J. Meskers
Summary: Detection of circular polarization of light using chiral semiconductors is not well understood. A simple experiment using semi-transparent chiral photodiodes reveals that changing the direction of illumination on organic bulk-heterojunction cells leads to a reversal of circular selectivity in photocurrent generation. This can be explained by a space-charge limitation and preferential absorption of one circular polarization of light by the chiral non-fullerene acceptor.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Xiao Ma, Haijun Bin, Bas T. T. van Gorkom, Tom P. A. van der Pol, Matthew J. J. Dyson, Christ H. L. Weijtens, Marco Fattori, Stefan C. J. Meskers, Albert J. J. M. van Breemen, Daniel Tordera, Rene A. J. Janssen, Gerwin H. H. Gelinck
Summary: Organic bulk heterojunction photodiodes (OPDs) are attracting attention in sensing and imaging. The detectivity of these OPDs is often limited by a substantial reverse bias dark current density (J(d)). Recent studies have shown that thermal charge generation mediated by mid-gap states is responsible for J(d). The temperature dependence of J(d) in state-of-the-art OPDs is reported in this study, and it is found that the dark current is attributed to thermal charge generation at the donor-acceptor interface mediated by intra-gap states near the band edges.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Robin Ammenhaeuser, Patrick Klein, Eva Schmid, Sabrina Streicher, Jan Vogelsang, Christian W. Lehmann, John M. Lupton, Stefan C. J. Meskers, Ullrich Scherf
Summary: This article reports the synthesis of helical polymers with a rigid square structure based on spiro-linked ladder-type pentaphenyl units. The variation of circular dichroism with increasing chain length provides direct evidence for delocalization of electronic excitations over at least 10 monomeric units. The change in the degree of circular polarization of the fluorescence across the vibronic side bands shows that vibrational motion can localize the excitation dynamically to almost one single unit.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Physics, Applied
Yun Li, Girish Lakhwani
Summary: The output characteristics and lasing threshold behavior of higher order Bragg lasers with organic active layer spin-cast over fused-silica gratings are investigated. Different duty cycle gratings ranging from 1st to the 400th Bragg order are fabricated using standard e-beam lithography. Variation in thresholds with duty cycle and a dramatic reduction in threshold with increasing cavity length are observed. The lowest lasing thresholds obtained for 4th and 400th order distributed feedback lasers are approximately 1.4 and 4 mu J cm(-2), respectively, using F8(0.9)BT(0.1) as an active layer. 400th order Bragg lasers fabricated with direct-write photolithography show comparable thresholds to e-beam lithography fabricated devices.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Medicinal
Chidambar Kulkarni, Hirotoshi Sakaino, Ghislaine Vantomme, Stefan C. J. Meskers
Summary: When irradiating a molecular material with pure circularly polarized light, a certain handedness can be imprinted into the material. To study the mechanism and kinetics of this process, a new chiroptical tool has been developed to monitor the circular polarization of the incident light after transmission through the photoactive layer. Kinetic Monte Carlo simulations on a model for the active material support the interpretation of a transient minimum in the degree of circular polarization as a nematic transient state during photo-inversion of a cholesteric organization.
Article
Chemistry, Multidisciplinary
Lixuan Liu, Zhixiang Wei, Stefan C. J. Meskers
Summary: Non-fullerene acceptor molecules in organic solar cells have strong absorption band in near-infrared. In solid phase, the interaction between light and molecular excitation can induce formation of polaritons. Reflection spectra for Y6-type polycrystalline films of a non-fullerene acceptor exhibit a signature of polaritons with a local minimum associated with allowed molecular transition. This minimum in reflection enhances the entry of light into the solid, resulting in a local maximum in external quantum efficiency of pure acceptor photovoltaic cells.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Review
Chemistry, Multidisciplinary
Daniel J. Tibben, Gus O. Bonin, Inseong Cho, Girish Lakhwani, James Hutchison, Daniel E. Gomez
Summary: Research into strong light-matter interactions continues to fascinate, driven by surprising experimental observations. Strong light-matter interactions have been found to significantly alter the properties of materials, particularly in intermolecular energy transfer. This review provides a concise account of the fundamental concepts of intermolecular energy transfer and how they are modified by strong light-matter interactions, highlighting recent experimental advances and the potential for future research in this exciting field.
Article
Multidisciplinary Sciences
Riccardo Ollearo, Xiao Ma, Hylke B. Akkerman, Marco Fattori, Matthew J. Dyson, Albert J. J. M. van Breemen, Stefan C. J. Meskers, Wijnand Dijkstra, Rene A. J. Janssen, Gerwin H. Gelinck
Summary: Remote measurement of vital sign parameters is a challenging task that requires the use of large-field-of-view, easy-to-integrate unobtrusive sensors. In this study, we present a narrowband solution-processed thin-film photodiode with high NIR responsivity, low dark currents, and operational stability. The device shows superior tolerance to background light compared to silicon-based sensors and has potential for remote monitoring of heart rate and respiration rate.
Article
Chemistry, Multidisciplinary
Xiao Ma, Riccardo Ollearo, Bas T. van Gorkom, Christ H. L. Weijtens, Marco Fattori, Stefan C. J. Meskers, Albert J. J. M. van Breemen, Rene A. J. Janssen, Gerwin H. Gelinck
Summary: Trap states in organic semiconductors, particularly in bulk-heterojunction photodiodes, have been investigated using three sensitive techniques. The study reveals that intra-gap states in the polymers, lying above the energy of the highest occupied molecular orbital, are responsible for the reverse-bias dark current density. The results emphasize the importance of reducing the energy and density of these intra-gap states for improving the performance of near-infrared organic photodiodes.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Review
Chemistry, Multidisciplinary
Lyndon A. Hall, Deanna M. D'Alessandro, Girish Lakhwani
Summary: Recently, there is growing interest in the use of chiral metal-organic frameworks (MOFs) and coordination polymers (CPs) for photonics applications. These materials offer the ability to tune their properties and realize new functionalities through the selection of metal and ligand components. This review focuses on the synthesis of chiral MOFs and CPs, their recent innovations in optical and photonics applications, as well as the challenges and potential solutions in this field. Overall, chiral MOFs and CPs show great promise for future technologies such as optical communication and computing, optical displays, and all-optical devices.
CHEMICAL SOCIETY REVIEWS
(2023)
Article
Chemistry, Inorganic & Nuclear
Debsouri Kundu, Natalia del Rio, Marie Cordier, Nicolas Vanthuyne, Emma V. Puttock, Stefan C. J. Meskers, J. A. Gareth Williams, Monika Srebro-Hooper, Jeanne Crassous
Summary: The preparation, structural and spectroscopic characterization of the first enantiopure cycloplatinated complexes with a bidentate, helicenic N-heterocyclic carbene and a diketonate ancillary ligand were investigated through experimental and computational studies. These complexes exhibit long-lived circularly polarized phosphorescence, with dissymmetry factor g(lum) values >= 10(-3) in solution, doped films at room temperature, and around 10(-2) in a frozen glass at 77 K.
DALTON TRANSACTIONS
(2023)
Article
Chemistry, Multidisciplinary
Lixuan Liu, Zhixiang Wei, Stefan C. J. Meskers
Summary: Non-fullerene acceptor molecules in organic solar cells exhibit strong absorption in the near-infrared range. The interaction between light and molecular excitation induces the formation of polaritons in the solid phase. Reflection spectra of polycrystalline films of a Y6-type non-fullerene acceptor indeed exhibit features of polaritons. The local minimum in the reflection band corresponds to allowed molecular transitions, allowing efficient light entry and resulting in a local maximum in external quantum efficiency of the pure acceptor-based photovoltaic cell.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Stefan C. J. Meskers
Summary: In assemblies of identical molecules or chromophores, electronic excitations can be described as excitons, which are bound electron-hole pairs that move from site to site in a coherent manner. Understanding excitons is crucial for tailoring favorable photophysical properties in organic molecular systems. However, the limitations of exciton concept have become evident as excitons can hybridize with photons and phonons. To address these issues, this article discusses excitons within the broader context of the gauge properties of the electromagnetic force.
Article
Materials Science, Multidisciplinary
Inseong Cho, William J. Kendrick, Alexandra N. Stuart, Pria Ramkissoon, Kenneth P. Ghiggino, Wallace W. H. Wong, Girish Lakhwani
Summary: This study demonstrates the suppression of excimer emission and the enhancement of energy transfer in TADF emitters through strong light-matter coupling, leading to efficient organic light-emitting diodes with high color purity.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Materials Science, Multidisciplinary
Inseong Cho, William J. Kendrick, Alexandra N. Stuart, Pria Ramkissoon, Kenneth P. Ghiggino, Wallace W. H. Wong, Girish Lakhwani
Summary: Strong light-matter coupling is exploited as a way to reduce aggregation-induced excimer losses in multi-resonance thermally activated delayed fluorescence emitters.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
