The effect of interchain coupling on the formation and the stability of a biexciton is studied in poly （p-phenylene vinylene） chains in the framework of the tight-binding approach. We obtain an intrachain exciton and biexciton as well as an interchain exciton and biexciton through a double-photon excitation.It is found that a biexciton is energetically favourable to two single excitons even when there exists an interchain coupling.There is a turnover value t⊥c of the interchain coupling for the formation of a biexciton,beyond which two excitons are combined into one biexciton.The binding energy of a biexciton is calculated to decrease with the increase of interchain coupling,which indicates that a biexciton is relatively stable in polymers with a weak interchain coupling.The conclusion is consistent with the experimental observations.In addition,a suggestion about how to improve the yielding efficiency or the formation of biexcitons in actual applications is given.
