P‐114: New Dyes for Red Emitting OLED

Abstract

The variation of the structural elements in donor-acceptor substituted polyenes 1 (A 1 = A 2 = CN, R 1 and R 2 form a cyclohexene or pyrane ring, D is an amino substituted phenyl or thiophene ring) influence very much their thermal, emissive and photo-electronic properties.The contribution shows that the emission can be varied from 630 nm to almost 714 nm. The performance data in a typical device are given and discussed in detail. The substitution pattern influence the thermal properties of the dyes 1 as well. Just by introduction of F-atoms in the cyclohexene derivatives the thermal behaviour can be influenced very positively, which is of particular interest for the technical use of the dyes. IntroductionDonor-acceptor substituted polyenes 1 are known for a long time and they are useful materials, e. g. as fluorescence dyes [1], as materials in NLO applications [2], as dyes in photoelectrophoretic materials [3] or as sensitising dyes in silver halide emulsions [4].Since the early years of OLED, DCM 1a (A 1 , A 2 = CN; R 1 , R 2 form a methyl substituted 1,4-pyrane-ring and D means N,Ndimethylamino-phenyl) and derivatives, like DCM 2, DCJ 1b (A 1 , A 2 = CN, R 1 , R 2 , form a 1,4-pyrane-ring and D is the julolidinyl-moiety) or DCJTB 1c (A 1 , A 2 = CN, R 1 , R 2 , form a 1,4-pyrane-ring with a t butyl substituent and D is the tetramethyljulolidinyl-moiety) have been described as orange to red emitters when used as dopants for Alq 3 [5,7]. Since the report of organic light emitting diodes at the Second International Symposium on Chemistry of Functional Dyes [6] a lot of affords were made to change the only red orange colour of the diodes into the red region. Thus, DCM 1a emits light at about 590 nm, DCM 2 1b emits at 625 nm and DCJTB at 620 nm [7]. There are different goals to develop new dyes, e.g. to shift their emission more into the red region, to increase the life time or to increase their thermal stability, just to mention some. X.T. Tao et al. found, that alicyclic bridged derivatives DCDDC 1d (A 1 , A 2 = CN, R 1 , R 2 form a cyclohexene ring and D is the N,N-dimethylamino-phenyl-moiety) give more pure red light [8]. But this dyes form easily aggregates already at doping concentrations ~1 wt%, which is technologically disadvantageous. With the aim to overcome this and the above mentioned problems we have synthesised and characterised new red-emitting dopants. ResultsBy the reaction of 2-t butyl-6-methyl-4-dicyano-methylen-pyranes 2, 2-phenyl-4-dicyano-methylen-5,6-cyclohexano-pyranes 3, 2,3-cyclopenteno-chromone 4 and heterocyclic aldehydes 5 in acetonitril, DMF or ethanol we obtained heterocyclic pyrane derivatives 6, Fig. 2. NC CN S X NR 2 O R 1 R 5 R 2 R 3 R 4 X S R 2 N O R 5 O NC CN O NC CN O NC CN 2 3 4 5 6 Fig. 2 9 NC CN N O R 1 R 2 R 2 R 3 R 5 R 4 N O R 2 R 3 N R 1 R 6 NC CN R 2 R 3 R 4 R 5 7 10 8 11 N NC CN R 2 R 3Fig. 3The 4-dicyanomethylen-cyclohexene derivatives 10, 11 are prepared by the reaction of 2,2,6-trimethyl-4-dicyano-methylenecyclohexene 7, 9-formyl-julolidines 8 and 8-formyl-6...