[21a-W521-1~10] 12.4 有機EL・トランジスタ

▲ [21a-W521-3] Quasi-continuous-wave lasing in a solvent-free liquid molecular semiconductor

〇Ribierre JeanCharles^1,2、Sandanayaka Atula S.D.^1,2、Kim Ju-Hyung³、Pitrat Delphine⁴、Zhao Li¹、Matsushima Toshinori^1,2、Andraud Chantal⁴、Adachi Chihaya^1,2 (1.OPERA, Kyushu Univ.、2.JST ERATO、3.Pukyong Univ.、4.ENS Lyon)

キーワード：liquid molecular semiconductor,organic DFB laser,continuous wave lasing

We report on the fabrication of quasi-continuous-wave (quasi-cw) organic semiconductor distributed feedback (DFB) lasers based on a gain medium containing a solvent-free liquid 9-(2-ethylhexyl) carbazole (EHCz) host doped with a highly fluorescent heptafluorene derivative.^1,2 In order to suppress the triplet losses in the quasi-cw regime, we introduce oxygen as triplet scavenger in the gain medium by simply bubbling the liquid semiconductor with oxygen for 10 minutes. The presence of oxygen in the solvent-free liquid does not lead to any quenching of the singlet excitons. However, singlet-triplet exciton annihilation leading to a significant quenching of the emission at high excitation intensities is nearly suppressed.The influence of the oxygenation on the properties of the quasi-cw DFB lasers is then investigated in details by optically-pumping these devices with 10 ps pulses at various repetition rates. The oxygenated DFB lasers show a threshold of about 2 microJ/cm², which is lower than that obtained in nitrogenated liquid devices and which is independent of the repetition rate in the range between 10 kHz and 4 MHz. Overall, this study demonstrates that the use of oxygen as triplet quencher is very promising for the development of optically-pumped cw organic semiconductor lasers.

[1] E. Y. Choi et al., Opt. Express 21, 11368 (2013).
[2] J.H. Kim, M. Inoue, L. Zhao, T. Komino, S. Seo, J.C. Ribierre and C. Adachi, Appl. Phys. Lett. 106, 053302 (2015).
[3] L. Zhao, M. Inoue, K. Yoshida, A.S.D. Sandanayaka, J.H. Kim, J.C. Ribierre and C. Adachi, IEEE J. Sel. Top. Quant. Electron. 22, 1300209 (2016).