Fast Response Blue and Green Organic Light Sources with Different Fluorescence Lifetime Materials for the Wavelength Division Multiplexing Optical Interconnect Application

We have demonstrated fast response blue and green organic light-emitting diodes (OLEDs) for optical interconnect applications. A fluorescence lifetime (FL) of an organic light-emitting layer (EML) was important parameter to increase a transmission speed of an OLED light source. We examined transient properties of the OLED with a short FL material as an EML. We have found that three species of organic materials have short FLs, which were 1.4 ns, 0.8 ns, and 1.6 ns for the l,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DSB), 4,4-bis(2,2-diphenyl-ethen-l-yl)-diphenyl, and 4,4´-bis(9-ethyl-3-carbazovinylene)-l,l´-biphenyl doped in 4,4´-bis(9-dicarbazolyl)-2,2´-biphenyl (CBP) films, respectively. These FLs are much shorter than that of tris(8- hydroxyquinoline)aluminum (Alq₃), which was generally used as the EML. As a result, we have achieved the increase of the transmission speed by using the short FL material. In order to investigate the transmission speed of the OLED, we investigated the frequency dependence of an output power. It was found that the transmission speed of the blue OLED faster than that of the conventional green device owing to the shorter FL of the blue emitting material. Furthermore, we have achieved the -3 dB cutoff frequency of 15 MHz by utilizing 0.5- wt.% DSB doped in CBP as the EML. We have also investigated the frequency dependence of the photoluminescence intensity to estimate the influence of the FL on the transmission speed. The -3 dB cutoff frequencies were 20 MHz and 160 MHz for 0.5- wt.% 5,6,11,12-tetraphenyl-tetracene doped Alq3 and non doped DSB films, of which the FLs are 9.2 ns and 2.0 ns, respectively.