International Journal of

---

In this article, we report the studies of various device architectures of organic lightemitting devices (OLEDs) incorporating highly efficient blue-emitting and ambipolar carriertransport ter(9,9-diarylfluorene)s, and their influences on device characteristics. The device structures investigated include single-layer devices and multilayer heterostructure devices employing the terfluorene as one functional layer. It is found that, although these terfluorenes are capable of bipolar carrier transport, rather poor device performance of single-layer devices in comparison with multilayer devices indicates that the heterostructure is still essential for balancing hole/electron injection and currents, for achieving high emission efficiencies, and for full utilization of high luminescence efficiency of these terfluorenes. With the heterostructure of hole-transport layer/terfluorene/electrontransport layer and careful choice of carriertransport materials, effective hole and electron injection, confinement of carriers, and confinement of excitons in terfluorenes are achieved. As a consequence, a highly efficient (4.1% quantum efficiency), low-voltage (~2.5 V turn-on voltage), and color-saturated nondoped blue-emitting device is demonstrated. Such high electroluminescent efficiency is consistent with high photoluminescent quantum yields of these terfluorenes and is competitive with those of efficient doped blue OLEDs.

---

The value of ozone absorption cross section (OACS) is a key parameter used in the configuration of gas sensors. Sadly, the variations of certain parameters among others such as temperature, pressure, and optical path-length in a given spectrum can affect the values of OACS. As a result, there have been several discrepancies in the value of OACS. Recently, the simultaneous effects of optical path-length were investigated in the visible spectrum. Hence, there is the need to also carry out the same investigation in the UV spectrum.  So, in this paper, we have reported the combined variation effects of temperature (100 K–350 K), and optical path-length (0.75 cm–130 cm) on OACS in the UV spectrum. We used the method of optical absorption spectroscopy as deployed in a model software called Spectralcalc. The software comprising the HITRAN12 latest line list was used to simulate OACS values. Simulated results were obtained using the latest available line list on the HITRAN12 Spectralcalc simulator. Our obtained results were slightly different from those reported for the visible spectrum but followed a similar trend, in that it showed a decrease in the OACS with an increase in the temperature from 100 K to 350 K at 279.95 nm and 257.34 nm by 1.09 % and 1.43 % respectively. While optical path-length had zero effect on it. We, therefore, conclude that at constant pressure, OACS depends on both temperature and absorption wavelength but not on optical path-length. The analysis reported in this work only seeks to address the differences in the OACS relative to temperature in the UV spectrum. So, the results obtained in this paper can be used to optimally configure ozone gas sensors to obtain an accurate measurement.