Charge transport materials having at least a metallocene group

Improved charge transport material comprises the formula: where M comprises a metallocenyl group; Y comprises a functional group selected from the group consisting of a metallocenyl group, a hydrazone group, an azine group, a reactive ring group, an ethylenically unsaturated group, and combinations thereof; R1 and R2 comprise, each independently, H, an organic group, or an organometallic group; and X is a bond, O, S, an aminylene group, a sulfonyl group, an organic linking group, or a combination thereof.