White and blue temperature stable and efficient OLEDs using amorphous spiro transport and spiro emitting compounds

Abstract

The temperature stability of white and blue OLEDs was investigated by observing the I-V, EL-V and the spectral characteristics of various devices stored at elevated temperature (up to 130 degrees Celsius). Blue multilayer organic light emitting diodes (OLEDs) containing PEDT (polyethylenedioxythiophene) or PANI (polyaniline) derivatives as the hole injection and puffer layer, aromatic diamines like Spiro-TAD (2,2',7,7'- tetrakis(diphenylamino)spiro-9,9'-bifluorene) as a hole transport material (HTM), Spiro-DPVBi (2,2',7,7'- tetrakis(2,2-diphenylvinyl)spiro-9,9'-bifluorene) as an emitting material (EM) and of Alq<SUB>3</SUB> (tris(8-hydroxy- quinoline)aluminum) as the electron-injection and electron- transport layer (ETL) were fabricated. White OLEDs were prepared, containing an additional DCM (dicyanmethylene-2- methyl-6-(p-dimethylaminostyryl)-4H-pyran) doped Alq<SUB>3</SUB> layer between the Spiro-DPVBi and Alq<SUB>3</SUB> layer. Use of Spiro-TAD as a hole transport material (HTM) and of Spiro- DPVBi as an emitting material (EM) resulted in dramatically improved temperature stability: for the white and blue OLED no significant deterioration up to 130 degrees Celsius were found. Devices consisting of non spiro components like NPB and/or DPVBi already started to degrade at much lower temperatures.