Wavelength dependence of reversible photodegradation of disperse orange 11 dye-doped PMMA thin films

TL;DR

This study investigates how the wavelength affects reversible photodegradation in DO11 dye-doped PMMA films, revealing wavelength-independent recovery rates and high photostability, with implications for understanding decay mechanisms.

Contribution

It provides the first detailed measurement of wavelength dependence of reversible photodegradation in DO11/PMMA, supporting the correlated chromophore domain model and highlighting the system's high photostability.

Findings

Reversible and irreversible IQEs are constant across wavelengths.

Recovery rate is independent of wavelength.

DO11/PMMA exhibits high photostability among organic dyes.

Abstract

Using transmittance imaging microscopy we measure the wavelength dependence of reversible photodegradation in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA). The reversible and irreversible inverse quantum efficiencies (IQEs) are found to be constant over the spectral region investigated, with the average reversible IQE being $\overline{B}_\alpha= 8.70 (\pm 0.38)\times 10^5$ and the average irreversible IQE being $\overline{B}_\epsilon= 1.396 (\pm 0.031)\times 10^8$. The large difference between the IQEs is hypothesized to be due to the reversible decay channel being a direct decay mechanism of the dye, while the irreversible decay channel is an indirect mechanism, with the dye first absorbing light, then heating the surrounding environment causing polymer chain scission and cross linking. Additionally, the DO11/PMMA's irreversible IQE is found to be among the largest of those reported for organic dyes, implying that the system is highly photostable. We also find that the recovery rate is independent of wavelength, with a value of $\overline{\beta}=3.88(\pm 0.47) \times 10^{-3}$ min$^{-1}$. These results are consistent with the correlated chromophore domain model of reversible photodegradation.