[13a-B11-1~10] 12.4 Organic light-emitting devices and organic transistors

▲ [13a-B11-6] Very Efficient Quasi-continuous-wave Lasing from Organic Semiconductor Films

〇SANGARANGE DONATULA SANDANAYAKA^1,2, Toshinori Matsushima^1,2, Chihaya Adachi^1,2 (1.OPERA, Kyushu University, 2.JST, ERATO)

Keywords:organic semiconductor films, Quasi-continuous-wave, Organic laser

The realization of efficient quasi-continuous-wave (qCW) lasing from organic semiconductor films under optical pumping is desired. In this sudy, we demonstrated efficient qCW lasing with reduced threshold (E_th) and increased repetition rate (f) by employing a doping technique, a mixed order grating (Fig. 1a), and a polymer overcoating film. The value of E_th obtained from a neat film of 4,4’-bis[(N-carbazole)styryl]biphenyl (BSBCz) embedded into a second-order grating was relatively high (Fig. 2b). Doping BSBCz into a host film of 4,4’-bis(N-carbazolyl)-1,1’-biphenyl (CBP) resulted in a reduction of E_th due to suppressed concentration quenching. The E_th was further reduced by replacing the second-order grating with a mixed order grating containing the second-order grating combined with a first-order grating. The qCW lasing at a very high f was difficult because of the ablation of the semiconductor film by strong excitation. To suppress the ablation, the semiconductor film was covered with a thick polymer film by spin coating. In this sample, we could realize a very high f of up to 80 MHz along with a very low E_th of 0.08−0.25 mJ cm⁻², which is ten-fold higher than a previous record f of 8 MHz.¹ These results would be useful for realizing reliable, cost-effective organic laser diodes in the future.