PNNL

Abstract

We report an alternative, high yielding synthesis for the known compound 2,4,6-tris(2',4'-difluoro-[1,1'-biphenyl]-4-yl)-1,3,5-triazine, (tris-(dFB)Tz). The lowest occupied molecular orbital energy for tris-(dFB)Tz is calculated to be -3.5 eV via electrochemical characterization. The deep ELUMO of tris-(dFB)Tz affords a material with excellent electron acceptor characteristics for use in n-doped electron transport layers. Tris-(dFB)Tz shows a four order of magnitude increase in the number of carriers upon doping with 8 wt.% Cs2CO3. Enhanced electron injection was also observed upon doping with Cs2CO3, eliminating the need for a LiF injection layer. Blue phosphorescent OLEDs were fabricated using n-doped tris-(dFB)Tz electron transport layers. OLEDs with thick (700Å) Cs2CO3 doped tris-(dFB)Tz electron transport layers had lower operating voltage than OLEDS with an undoped electron transport layer of bis(diphenylphosphoryl)dibenzothiophene (PO15), which has previously been used in low voltage, high efficiency OLEDs. The tris-(dFB)Tz results indicate that aromatic substituted triazines may be promising materials for use as electron acceptors in n-doped organic electronic systems.