Singlet oxygen quenching of tris(8-hydroxyquinoline)aluminum (Alq3) and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1-biphenyl]-4,4-diamine (TPD)

Singlet oxygen (1O2, O2 (a1Δg)) quenching by the organic light emitting device (OLED) electron transport material tris(8-hydroxyquinoline)aluminum (Alq3) and hole transport material N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1-biphenyl]-4,4-diamine (TPD) in benzene has been investigated by measuring the 1270 nm phosphorescence of O2 (a1Δg→X3∑g−) following 532 nm irradiation of a C60 benzene solution. A 1O2 quenching rate constant of 1.65±0.20×108 l mol−1 s−1 is obtained for Alq3 with evidence of chemical quenching. The decrease in 1O2 phosphorescence upon TPD addition is primarily attributed to C60∗ quenching by TPD. Direct TPD quenching of 1O2 is not observed in the present experiment, leading to an upper limit estimate of the 1O2 quenching rate constant of 106 l mol−1 s−1.