Noncontact Temperature Measurements of Organic Layers in an Organic Light-Emitting Diode Using Wavenumber-Temperature Relations of Raman Bands

摘要

We have measured the temperatures of the organic layers in operating organic light-emitting diodes (OLEDs) by Raman spectroscopy. The wavenumbers of the Raman bands due to N,N'-di-naphthaleyl-N,N'-diphenyl-l,1'-biphenyl-4,4'-diamine (NPD) and copper phthalocyanine (CuPc) have been measured as a function of temperature in the range of 25-191 ℃. The observed positions of strong bands around 1607 cm~(-1) (NPD) and 1531 cm~(-1) (CuPc) shifted downward linearly with increasing temperature in the ranges lower than 92 and 191 ℃, respectively. We have determined the temperatures of the NPD and CuPc layers in an operating OLED from the wavenumber-temperature relations of these bands.