用积分球测定磷光材料的量子性质

磷光物质经常用作有机电致发光器件中的发光层，因为与只有单线态有助于发光的材料相比，磷光材料的三重态和单线态的辐射衰减增加了其量子效率。这些磷光材料必须具有一定的量子效率才能用于实际目的。量子效率定义为样品吸收的光子数量与样品发射的光子数量之比。Application NoteFP-0006 Determining the Quantum Efficiency ofPhosphorescent Materials using an Integrating Sphere2/4Application Note Determining the Quantum Efficiency o f Phosphorescent Materials using an Integrating Sphere Introd u ction Phosphorescent substances are f req u ent l y used as the l uminescent l aye r in organic elect r oluminescent dev i ces since t he r adiat i ve decay from both the tr i plet and singlet states of phosphorescent mater i al increases i ts quantum ef f i c i ency，compar e d t o m ate ria ls where only th e singlet st a t e s contribute to l ig h t e mission.Th e s e phosp h oresc en t mater i als must have c e rtai n quantum e f f i ci en c ie s i n order to be used for practical purposes. Quantum effic i ency i s defined as the ratio of t h e number of photons absorbed by sam p le to the n umber of photons em i tted by s am ple FP-6500 Spe c trofl u oromete r To m e as u r e phos p hor e sc en t m aterials s uc h as films， an i nt e grat i ng spher e i s us e d. An i nt e grating sph e r e coll e cts t h e light t h at scatte r s off a su r face in di f ferent di r ect i ons and foc u ses that l ight to t h e detector ， as sh o wn i n Figure 1. While conventional integ r ating sphe r es can onl y m easure certain sample spectra a t room tempe r ature， the phosphorescence of n umerous samples can be observed if t he relaxation process i s s l owed down by cool i ng samples to 77 Kelv in . Th i s app li c a tion note demo n str a t e s t h e new dedicated syst e m developed for calcul a t in g qu a ntum e f f i c i ency from th e measu re d p hosphor e scence spectra at 77 K e lvi n . Keyword s Experi m en t al To obtain phosphorescence data with an i n tegrati n g sphe r e a Dewa r vessel， f il l ed wi t h coola n t suc h as l iquid n i t rogen， is plac e d i n the sphere and the spectrum of the i ncident light is measured as illustrated i n Figure 1. Figure 1. (L eft) D e w ar p o si t i on a n d (rig ht ) s a m pl e posi t i on i n i nte grat i n g s p here . T h e i n ciden t ph o ton (S ，) pea k a r ea appea r s in the excitat i on spect r um， i l lustrated i n blue in Figu r e 2. The sample is then placed i n side t h e Dewar vessel in the integrating sphe r e (Figure 1， r ight) and the sample's excitation and emiss i on spec tr a are measured . Figure 2 shows the exci t atio n a n d emi s sion of the scattering incident l ight. Th e excitation and em i ss i on peaks i n dic a te the n umber of p hoto n s unabsor b ed (S，) a nd emi tt ed (S，) b y the sample， respectively. T h e q u antum e f f ici e ncy i s calc u la t ed u s ing t h e fol l owi n g e quatio n： N um ber o f p h oto n s e m i tt e d b y sa mp l e S N umb er of p h oto n s a b s orbe d b y s a mp l e S ，-S， Figure 2. Excitation arid emission spectra of irciderit (blue) arid scattered (red) ph o ton s . Excitation Bandwidth 5nm Excitation Wavelength 350 (Quinine Sulfate)，335 (Benzophenone) nm Emission Bandwidth 5nm Data Interval 1nm Response Time 0.5 sec Scanning Speed 1000 nm/min R esu l ts To confi rm whet h er pl ac ing t h e Dewar vessel l a n d cool a n t i n the in t eg r ating sphere h a s a n y ef f ec t o n the measu r emen t r e sults， t h e f lu oresc e nce spect r um of a sample with a k nown q u ant u m ef f i ci en cy was measu r ed. Fig ur e 3 illus t ra t es the measured f luorescence spectrum and Table 1 shows the calcula t ed quantum eff i ciencies (中). The ca l culated fluorescence quan t u m efficiency was 0.56 while t he l iterat u re va l ue was 0.5462. These r esults indicate n o substantial effects whe n pla c ing a dewar inside the integrating sphere. Figure 3. Flu orescen c e s p ect r u m o f t h e in c i d e n t l i g ht (gre e n )， q u i n i n e sul f ate (b lu e)， and a 25x m or e c on c entr a te d qui n i n e su lf ate (r ed ) sa mp le . Table 1. F l u o rescence i n tensity and quant u m efficie n cy val u es o f qu i ni n e su l fate . A sample of benzophenone wa s cooled by l iquid n itrogen and placed in the in t egrating s p here. Figure 4 i ll ustrates the measured fluoresce n ce spectr um and Table 2 shows the calculated quantum efficiencies (中). The calculated phosphoresce n ce quantu m ef f ic i ency was 0.93 wh i le th e l i t erature va l ue was 0.903. I nt. Figure 4. Flu or es c ence s p ectrum of t h e i n cid e nt l ig ht (gr ee n )， b en z ophe n o n e (b lu e )，a n d a 25x mo r e co n cen t r a te d be n z o p h e n on e (re d ) s a m ple. Table 2. Flu or e scence i n t e n sity an d q ua nt u m e ffic ie n c y v al ues of be n z o p h e n on e . Conc lu s io n The quantum e f f iciency of p h os p h o resc e n t ma t eri al s a t l ow te m per a tur e s can r eli a bl y b e obtained using an FP-6500 and a dedica t ed qu a ntum eff i cie n cy syst e m. R efe r ence s 1. I n th is m ea s ur e m e nt ， th e Dewar v e ss el was fi ll e d with wat e r inst e ad of l i quid nitrogen 2. Mel h uis h ， W.H.， Journal of P hysical Chemistry. 65， 229，1961. 3. The Chemical Society of Japan， Courses i n Experimental Chemistry 3 Basic Physical Chemistry. Ap p l i c a t i o n Lib r ary： h t t p：//www.j asco i nc.com/ap p l i cati o n s