Pyridine Vapor Annealing Induced Reversible Switching Emission and Enhanced Electroluminescent Performance of Poly(fluorene-co-dibenzothiophene-S,S-dioxide)

In this article, we report on blue-green exciplex emission through pyridine solvent vapor annealing blue-light polymer PFSO10, which is comprised the strong electron-withdrawing dibenzo-thiophene-S,S-dioxide with the molar ratio of 10%. The photoluminescent spectrum of PFSO10 film emerged a fresh low-energy emission peaked at 482 nm after pyridine solvent vapor annealing, which was stemmed from the exciplex charge-transfer state between the PFSO10 and pyridine. It is worth noting that the exciplex emission peaked at 482 nm from the pyridine solvent vapor annealing film was disappeared after thermal annealed at 120 °C and its photoluminescent spectrum was similar to that of the pristine PFSO10 film. This similar phenomenon of photoluminescent spectrum was also occurred to the electroluminescent spectra of the PFSO10 films. Furthermore, the device performance of PFSO10 was achieved significant improvement after pyridine solvent vapor annealing. With optimizing the pyridine vapor annealing process, the device based on PFSO10 as emissive layer received a maximum luminous efficiency of 6.74 cd A⁻¹ with the peak brightness of 22,364 cd m⁻², which was enlarged over 140% compared to that of 2.77 cd A⁻¹ for the pristine PFSO10. These results demonstrate that appropriate solvent vapor annealing can be a simple and effective strategy to realize the reversible switching emission and improve the device performance.

Graphical Abstract