The relationship between photoconductivity and content of azo has been studied in double-layered photoreceptur devices where azo/titanium oxide phthalocyanine (TiOPc) composites were used as the charge generation materials (CGMs) and N,N'-diethyl-p-phenyl aldehyde biphenyl hydrazone (DENH) served as the charge transporting material (CTM). Composites of 3,3'-dichloro-4,4'-bis(1 "-azo-2"-hydroxy-3"-naphthoyl-o-chloroanide) biphenyl (DBCL) and TiOPc change photosensitivity with the content of DBCL, and two maximums were observed at 5 and 60% (by weight), respectively. Composites of 4,4'-bis (1 "-azo-2"-hydroxy-3 "-naphthoyl-o-chloroanide)biphenyl ether (DBO) and TiOPc show two maximums at 25 and 68%, respectively, while two maximums at 8 and 70% were recorded fur composites of TiOPc with 4,4'-bis(1"-azo-2"-hydroxy-3"-naphthoyl-o-chloroanide) biphenyl (AZO-AS). Results from ESR measurements indicate that there exists a charge transfer from azos to TiOPc. Different contents of TiOPc change the degree of the charge transfer, resulting in various xerographic properties of the composites. (C) 2002 Published by Elsevier Science B.V.