Excitonic origin of long-wavelength fluorescence in crystalline DAST
Abstract
Long-wavelength photoluminescence in crystalline 4- N, N -dimethylamino-4′- N ′-methylstilbazolium tosylate (DAST) has been repeatedly observed, yet its physical origin has remained unresolved. In contrast to solution-phase emission, this red-shifted fluorescence is characteristic of the crystalline state, indicating an intrinsic lattice-related mechanism. Here, experimental spectroscopy is combined with a structure-derived excitonic model based on the crystallographic arrangement of DAST chromophores. The model reveals a low-energy collective exciton state near 1.7 eV, in quantitative agreement with the observed Form III emission. The results demonstrate that structural non-equivalence within the unit cell plays a decisive role in stabilizing low-energy emissive excitonic states in organic ionic crystals.
Fields of Study & Subjects
Spectroscopy and Quantum Chemical Studies
Perovskite Materials and Applications
Strong Light-Matter Interactions
Publication details
- Journal / source
- Optical Materials Express
- Publisher
- Optica Publishing Group
- Volume
- 16
- Issue
- 7
- Pages
- 2177–2177
- Publication date
- 17 April 2026
- Language
- EN