We have developed an apparatus (Hamamatsu C9920-02) for measuring the absolute photoluminescence quantum yield.
This system consists of an excitation light source, a sample holder mounted in an integrating sphere and a multi-channel
CCD spectrometer. Using this apparatus, the absolute phosphorescence quantum yields were measured for several
iridium complexes doped in organic thin films or dissolved in deaerated solutions. The iridium complexes fac-tris
(2-phenylpyridine)iridium(III) (Ir(ppy)3) and its derivatives, showed high phosphorescence quantum yields (>90 %), while
bis(2-(2'-benzo(4,5-a)thienyl)pyridinato-N,C3')iridium(III)(acetylacetonate) (Btp2Ir(acac)) gave a lower
phosphorescence quantum yield (less than 40 %). To reveal the mechanism of nonradiative decay of the excited iridium
complexes, we made time-resolved photoacoustic measurements. It was found that all of the iridium complexes undergo
S1-T1 intersystem crossing with efficiencies of close to 100 % after photoexcitation. This indicates that the lower
phosphorescence quantum yield for Btp2Ir(acac) is due to involvement of the T1-S0 intersystem crossing process.
A highly sensitive framing streak camera which works in two types of operation, framing and streak, with 3 plug-ins (framing, fast, and slow streak) has been developed. In both operations, a gate extinction ratio of more than 1:107 has been achieved by double gate operation at the photocathode and the built-in micro channel plate. The framing plug-in has a framing speed up to 3 million frames/sec, with the shortest exposure time of 50 ns. The frame number can be easily changed. Exposure time and frame interval time can be set for each frame, respectively. The fast plug-in offers temporal resolution of better than 10 ps in the fastest sweep range and 25 mm useful photocathode length. The slow plug-in provides time windows from 50 ns to 10 ms/40 mm in 17 ranges.