Temperature measurements of organic light-emitting diodes by stokes and anti-stokes Raman scattering

We have measured the Stokes and anti-Stokes Raman scattering from organic light-emitting diodes based on copper phthalocyanine (CuPc), N,N'-di-1-naphthalenyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (alpha-NPD), and tris(8-quinolinolate) aluminum(III) (Alq(3)) with excitation at 633 nm. All of the observed bands have been attributed to CuPc because of the resonance Raman effect. The temperature of the CuPc layer has been obtained by taking the intensity ratio of anti-Stokes to Stokes Raman scattering of the 483 cm(-1) vibration. The temperature of the CuPc layer in the device operated at 400 mA was 140 degrees C.