Singlet fission(SF)is a photochemical process where a singlet excited chromophore shares its energy(ES1)with a ground-state neighbor chromophore to produce two triplet excited molecules(ET1).[1] The diradical character can be used to screen materials for singlet fission[2].In this work,the spin-projected unrestricted Hartree-Fock method is employed to evaluate the multiple diradical characters y0 and y1 of a series of heteroatom-doping π-conjugated acenes.It turns out that such heteroacenes have better diradical character than acenes and they do not exhibit obvious tetraradical character(y1/y0 > 0.2 and 0.2 < y0 < 0.6).The excitation energies of S1,T1 and T2 state are calculated by means of the time-dependent tuned long-range corrected density functional theory method with the Tamm-Dancoff approximation.On the basis of the diradical-character properties and energy level matching conditions(ES1≥2ET1 and ET2≥2ET1),our calculated results demonstrate that heteroacenes are possible candidates for energetically efficient singlet fission.The chalcogen-containing heteroacenes are better than N-doped acenes as singlet-fission materials.