Understanding Of Excited-state Dynamics Research Articles

Probing the excited state dynamics in perinone molecules for photovoltaic applications using transient absorption spectroscopy.

Nonfullerene polyaromatic molecules such as perinone are emerging as alternatives to fullerene derivatives due to their low manufacturing cost, ease of functionalization, and processing to improve the efficiency of optoelectronic devices. In this paper, we have used ultrafast transient absorption (TA) spectroscopy to probe the excited state dynamics in cis and trans perinone molecules. We have performed TA measurements in solution as well as thin films to provide a comprehensive understanding of excited-state processes occurring in cis and trans perinone molecules. Our results reveal the triplet state formation in perinone thin films through intersystem crossing and provide an in-depth understanding of the relaxation pathways of perinone molecules, which will be beneficial for designing and optimizing the device efficiencies of perinone based photovoltaic devices.

Photophysical investigation into room-temperature emission from xanthene derivatives.

The photophysical consequences of replacing the nitrogen heteroatom in phenothiazine with methylene are investigated for both solutions and crystalline solids. We analysed the excited state dynamics of four xanthene derivatives and observed an anomalous fluorescence from an energy level higher than the S1 state with lifetimes between 2.8 ns and 5.8 ns in solution and as solids. Additionally, the solid-state xanthene derivatives exhibited long-lived emission consistent with a triplet excited state, displaying millisecond lifetimes that ranged from 0.1 ms to 3.4 ms at ambient temperature in air. Our findings were supported by optical studies, crystallographic structural analyses, and DFT computations, which corroborated the photophysical measurements. It was concluded that the presence of the nitrogen atom in phenothiazine is crucial for achieving ultra-long emission lifetimes and that these results contribute to a deeper understanding of excited state dynamics which have potential implications for applications, such as display technologies, anticounterfeiting technologies, and sensors.

Correlative Dark-Field and Photoluminescence Spectroscopy of Individual Plasmon–Molecule Hybrid Nanostructures in a Strong Coupling Regime

Light-matter interactions play a crucial role in several prominent nano-optical phenomena, such as plasmon-mediated fluorescence, nanoscale lasing, and strong plasmon-exciton coupling. The latter holds promise for the development of nanoscale nonlinear optical schemes and room-temperature polaritonic lasers. In recent years, strong coupling in nanoscale plasmon-exciton systems, also known as plasmon-exciton polaritons, has been thoroughly investigated using transmission, reflection, and dark-field scattering spectroscopies. However, only a few recent studies performed experiments using photoluminescence spectroscopy on the individual hybrid nanostructure level. The latter is important for the detailed understanding of intrinsic excited state dynamics in strongly coupled systems. Here, we use correlative dark-field scattering (DF) and photoluminescence (PL) measurements to study polaritonic states in individual silver nanoprisms surrounded by molecular J-aggregates. We investigate these systems under various experimental conditions, including temperatures in the range T = 4-300 K, laser excitation wavelengths at 532, 568, and 640 nm, and a broad range of plasmon-exciton detunings. Our findings indicate that the lower energy peak in PL emission closely follows the lower polariton band observed in DF, while the higher energy PL peak follows the emission of uncoupled J-aggregate molecules and incoherent states. These observations further improve the understanding of excited state dynamics in strongly coupled plasmon-exciton systems.

Is there an Excited State Proton Transfer in phenol (or 1 -naphthol)-ammonia clusters? Hydrogen Detachment and Transfer to Solvent: A key for non-radiative processes in clusters

This contribution highlights recent advances in the understanding of excited state dynamics in aromatic enols. This review will be mainly focused on the experimental and theoretical work performed on two model systems, 1 -naphthol-ammonia and phenol-ammonia, and most particularly on cluster studies. These systems have long been thought to be prototypes for the famous 'solvent-induced excited state proton transfer reaction', but recent results contradict this mechanism. The dynamics of these systems, excited in the S 1 ( ~ ~ *) state, is not governed by couplings with ion pair states, inducing intracluster proton transfer, but rather linked to a crossing with a higher excited singlet state of the ~ σ * Rydberg state character, dissociative along the OH coordinate, leading to a hydrogen transfer from the hydroxyl group to the ammonia cluster via a non-adiabatic process, a mechanism also referred to as 'concerted electron and proton transfer'. The crossing of the higher 1 ~ σ * state with lower excited 1 ~ ~ * and ground states seems to be a general property in aromatic enols and azines (indole derivatives) and can help to understand the non-radiative decays in amino acid molecules as well as in DNA bases.