Improved thermal stability of nonpolymeric organic glasses by doping with fullerene C60

The doping of nonpolymeric organic glasses with C60 is found to improve their thermal stability. Films of triphenylamine dimer (TPD) N,N′-diphenyl-N,N′-(3-methyl-phenyl)-1,1′-biphenyl-4,4′-diamine, doped with fullerene C60 and 7,7,8,8-tetracyano-quinodimethane (TCNQ) on a level between 10 and 20 mol %, were prepared using vacuum codeposition techniques. While undoped and TCNQ-doped TPD films tend to crystallize under ambient conditions, no crystallization occurs on C60-doped TPD films on minimum doping level of 15 mol %. The crystallization can be suppressed even at temperatures about 333 K, the glass transition temperature of pure TPD, if the doping level of the C60-doped TPD films reaches 20 mol %.