A composition comprising a polymer represented by the following formula (i), wherein the composition exhibits photorefractive ability:
wherein R is selected from the group consisting of a linear alkyl group with up to 10 carbons, a branched alkyl group with up to 10 carbons, and an aromatic group with up to 10 carbons; n is an integer of 10 to 10,000; Z is a group which contains at least a tri-aromatic amine moiety shown in the structure (ii):
wherein Ra1-Ra14 are independently selected from the group consisting of a hydrogen atom, a linear alkyl group with up to 10 carbons, a branched alkyl group with up to 10 carbons, and an aromatic group with up to 10 carbons.