A spirofluorene-end-capped bis-stilbene derivative with a low amplified spontaneous emission threshold and balanced hole and electron mobilities

To realize high performance in electrically pumped organic semiconductor laser diodes, organic-gain materials with low thresholds of amplified spontaneous emission and laser and balanced hole and electron mobilities are required. However, it is still very difficult to find such well-balanced organic materials. In this study, we show that a spirofluorene-end-capped bis-stilbene derivative of 4-((E)-2-(9,9′-spirobi[fluoren]-3-yl)vinyl)-4'-((E)-2-(9,9′-spirobi[fluoren]-6-yl)vinyl)-1,1′-biphenyl (BSBSF) is an excellent gain medium with a low amplified spontaneous emission threshold of 0.66 μJ cm⁻² even in neat films. Additionally, the hole and electron mobilities of BSBSF films are very similar over a wide voltage range. Taking advantage of the balanced mobilities, we were able to obtain suppressed efficiency roll-off in BSBSF-based organic light-emitting diodes. These results will contribute toward fabrication of optically and electrically pumped organic semiconductor laser diodes with high performance.