Photoelectrochemical immunosensor for sensitive detection of alpha-fetoprotein based on a graphene honeycomb film

•A photoelectrochemical electrode was fabricated based on a graphene honeycomb film.•A fluorescent probe (AFP-PFBT-GOD) was synthesized for the detection current promotion.•This photoelectrochemical biosensor can sensitively detect alpha-fetoprotein by competitive immunoassay.•The photoelectrochemical biosensor has high detection sensitivity and good reliability.•The detection limit of alpha-fetoprotein is lower than 0.05 ng/mL.