Facile Synthetic Approach to Laser Chromophores with Fast Excited-State Dynamics, High Stability and Low ASE Thresholds

Abstract

Recent progress toward electrically pumped organic laser diodes has highlighted the demand for organic gain media that simultaneously exhibit ultralow lasing thresholds and long-term operational stability. However, organic laser dyes remain fundamentally limited by photochemical degradation, thermal instability, and excited-state loss processes under high excitation densities. Here, we report a simple synthetic strategy to enhance the performance of organic laser dyes through the selective elimination of photolabile functionalities while preserving fast excited-state dynamics. This targeted molecular simplification suppresses dominant photodegradation pathways particularly under intense continuous-wave optical pumping with ≥14 times enhancements. The resulting materials also possess ultrahigh radiative decay rates (up to 1.96 × 10⁹ s^–1), among the highest reported for organic lasing chromophores, together with fast excited-state lifetime (down to 0.47 ns) and a large stimulated emission cross-section of σ_em(λmax) = 6.7 × 10^–16 cm² (at 409 nm). These characteristics enable ultralow amplified spontaneous emission (ASE) thresholds of 0.72±0.02 (at 440 nm) and 0.64±0.04 µJ cm^–2 (at 436 nm) within the deep blue spectral regions for the neat and blend films of the new TFBPCz, where the new FBPCz also exhibits a record low solid-state ASE threshold values of 0.72±0.02 µJ cm^–2 at 414 nm for the blend film (and 0.76±0.02 µJ cm^–2 at 419 nm for neat films) in the near UV range. Importantly, stimulated emission is spectrally isolated from triplet absorption, effectively suppressing singlet–triplet annihilation and minimizing triplet-induced losses. Along with the enhanced photostability and thermal stability achieved through the molecular design, the combination of ultrafast radiative dynamics and high optical gain highlights these new materials as promising gain media for next-generation organic laser diodes and solid-state organic laser platforms.