Low-Threshold Light Amplification in Bifluorene Single Crystals: Role of the Trap States

Paulius Baronas, Gediminas Kreiza, Povilas Adomenas, Ona Adomeniene, Karolis Kazlauskas, Jean Charles Ribierre, Chihaya Adachi, Saulius Juršenas

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


Organic single crystals (SCs) expressing long-range periodicity and dense molecular packing are an attractive amplifying medium for the realization of electrically driven organic lasers. However, the amplified spontaneous emission (ASE) threshold (1-10 kW/cm2) of SCs is still significantly higher compared to those of amorphous neat or doped films. The current study addresses this issue by investigating ASE properties of rigid bridging group-containing bifluorene SCs. Introduction of the rigid bridges in bifluorenes enables considerable reduction of nonradiative decay, which, along with enhanced fluorescence quantum yield (72-82%) and short excited state lifetime (1.5-2.5 ns), results in high radiative decay rates (0.5 × 109 s-1) of the SCs, making them highly attractive for lasing applications. The revealed ASE threshold of 400 W/cm2 in acetylene-bridged bifluorene SCs is found to be among the lowest ever reported for organic crystals. Ultrafast transient absorption spectroscopy enabled one to disclose pronounced differences in the excited state dynamics of the studied SCs, pointing out the essential role of radiative traps in achieving a record low ASE threshold. Although the origin of the trap states was not completely unveiled, the obtained results clearly evidence that the crystal doping approach can be successful in achieving extremely low ASE thresholds required for electrically pumped organic laser.

Original languageEnglish
Pages (from-to)2768-2775
Number of pages8
JournalACS Applied Materials and Interfaces
Issue number3
Publication statusPublished - Jan 24 2018

All Science Journal Classification (ASJC) codes

  • General Materials Science


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