arXiv subjects

Tim Achenbach

Publications and source records attributed to Tim Achenbach.

6 recordsLinked to original sources

arXiv2026

Efficient purely organic phosphorescent emitters for programmable luminescent tags: from building blocks to donor-acceptor-donor structures

Purely organic room-temperature phosphorescence (RTP) emitters are key components of programmable luminescent tags (PLTs), photonic devices for rewritable information storage and UV dosimetry. In this work, we systematically explore the design space of donor-acceptor and donor-acceptor-donor organic phosphorescent emitters in symmetric and asymmetric architectures. Phenoxathiine (PX) is introduced as an alternative donor to thianthrene (TA), combined with benzophenone (BP) or pyridine (Py) as acceptors. Through photophysical characterization, quantum chemical simulations, and PLT device testing, we identify structure-property relationships and, in particular, investigate the impact of the individual moieties on the emission properties and stability. The RTP emission wavelength is primarily tunable through the donor moiety: PX-based emitters emit sky-blue ({\lambda}_P = 480 nm), while TA-based emitters emit in the green ({\lambda}_P = 520 nm) due to an increased Stokes shift. The acceptor unit strongly influences the phosphorescence quantum yield, with Py-based emitters systematically outperforming BP-based ones. All newly synthesized PX-containing emitters show sufficient performance in PLT devices, though with reduced photostability compared to TA-based counterparts. Together, these results demonstrate that systematic donor-acceptor design enables predictable control over RTP emission properties, advancing the rational development of high-performance RTP-based photonic devices.

cond-mat.mtrl-sci↗

arXiv2026

Nonclassical traits in multi-copy state discrimination

Quantum state discrimination is a fundamental information processing task that serves as a key component in many applications while also carrying foundational significance. In this work, we consider minimum error discrimination of multi-copy states, where instead of preparing a single system we assume that multiple instances of the same state are prepared. Now the discrimination allows for measurements from multiple parties with different measurement strategies varying from global measurement strategy to ones restricted to different forms of local operations and classical communication strategies. By comparing the average success probabilities in quantum and classical cases, we find a qubit strategy that outperforms all the bit strategies. On the other hand, we show that the classical measurement strategy does not give benefit in qubit over bit. However, we find that there are other (qu)bit-like operational theories which can outperform the best qubit strategies even with a classical measurement strategy and we are able to identify instances of different theories where different measurement strategies are optimal. In this way, we are able to find instances of nonlocality without entanglement as well as provide general bounds for bit-like operational theories.

quant-ph↗

arXiv2025

Factorization of multimeters: a unified view on nonclassical quantum phenomena

Quantum theory exhibits various nonclassical features, such as measurement incompatibility, contextuality, steering, and Bell nonlocality, which distinguish it from classical physics. These phenomena are often studied separately, but they possess deep interconnections. This work introduces a unified mathematical framework based on commuting diagrams that unifies them. By representing collections of measurements (multimeters) as maps to the set of column-stochastic matrices, we show that measurement compatibility and simulability correspond to specific factorizations of these maps through intermediate systems. We apply this framework to put forward connections between different nonclassical notions and provide factorization-based characterizations for steering assemblages and Bell correlations, including a new perspective on the CHSH inequality witnessing measurement incompatibility. We also investigate the symmetric $n$-extensions of multimeters and no-signaling behaviors and connect these extensions to a notion of $n$-wise compatibility and to the existence of $n$-wise LHV models, respectively. Furthermore, we investigate robustness to noise of nonlocal features by examining factorization conditions for maps involving noisy state spaces, providing geometric criteria for when noisy multimeters can be simulated by simpler measurement settings.

quant-ph↗

arXiv2022

Accurate wavelength tracking by exciton spin mixing

Wavelength discriminating systems typically consist of heavy benchtop-based instruments, comprising diffractive optics, moving parts, and adjacent detectors. For simple wavelengths measurements, such as lab-on-chip light source calibration or laser wavelength tracking, which do not require polychromatic analysis and cannot handle bulky spectroscopy instruments, light-weight, easy-to-process, and flexible single-pixel devices are attracting increasing attention. Here, we propose a device for wavelength tracking with room-temperature phosphorescence at the heart of its functionality that demonstrates a resolution down to one nanometer and below. It is solution-processed from a single host-guest system comprising organic room-temperature phosphors and colloidal quantum dots. The share of excited triplet states within the photoluminescent layer is dependent on the excitation wavelength and determines the afterglow intensity of the film, which is tracked by a simple photodetector. Finally, an all-organic thin-film wavelength sensor and two applications are demonstrated where our novel measurement concept successfully replaces a full spectrometer.

physics.optics↗

arXiv2020

High-speed and continuous-wave programmable luminescent tags

Most materials recently developed for room temperature phosphorescence (RTP) lack of practical relevance due to their inconvenient crystalline morphology. Using amorphous material systems instead, programmable luminescent tags (PLTs) based on organic biluminescent emitter molecules with easy processing and smooth sample shapes were presented recently. Here, the effective quenching of the emitters RTP by molecular oxygen (O2) and the consumption of the excited singlet O2 through a chemical reaction represent the central features. With customized activation schemes, high resolution content can be written and later erased multiple times into such films, providing a versatile yet simple photonic platform for information storage. However, two important limitations remain: (i) The immutable fluorescence of the emitters outshines the phosphorescent patterns by roughly one order of magnitude, allowing read-out of the PLTs only after the excitation source is turned off. (ii) The programming of these systems is a rather slow process, where lowest reported activation times are still > 8 s. Here, a material-focused approach to PLTs with fast activation times of 120 +/- 20 ms and high-contrast under continuous-wave (cw) illumination is demonstrated, leading to accelerated programming on industry relevant time scales and a simplified readout process both by eye and low cost cameras.

physics.app-ph↗

arXiv2017

Interplay of Fluorescence and Phosphorescence in Organic Biluminescent Emitters

Biluminescent organic emitters show simultaneous fluorescence and phosphorescence at room temperature. So far, the optimization of the room temperature phosphorescence (RTP) in these materials has drawn the attention of research. However, the continuous wave operation of these emitters will consequently turn them into systems with vastly imbalanced singlet and triplet populations, which is due to the respective excited state lifetimes. This study reports on the exciton dynamics of the biluminophore NPB (N,N-di(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine). In the extreme case, the singlet and triplet exciton lifetimes stretch from 3 ns to 300 ms, respectively. Through sample engineering and oxygen quenching experiments, the triplet exciton density can be controlled over several orders of magnitude allowing to studying exciton interactions between singlet and triplet manifolds. The results show, that singlet-triplet annihilation reduces the overall biluminescence efficiency already at moderate excitation levels. Additionally, the presented system represents an illustrative role model to study excitonic effects in organic materials.

physics.chem-ph↗